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Simply Easy Learning
ABOUT THE TUTORIAL
Hibernate Tutorial
Hibernate is a high-performance Object/Relational persistence and query service which is licensed under the
open source GNU Lesser General Public License (LGPL) and is free to download. Hibernate not only takes care
of the mapping from Java classes to database tables (and from Java data types to SQL data types), but also
provides data query and retrieval facilities.
This tutorial will teach you how to use Hibernate to develop your database based web applications in simple and
easy steps.
Audience
This tutorial is designed for Java programmers with a need to understand the Hibernate framework and API. After
completing this tutorial you will find yourself at a moderate level of expertise in using Hibernate from where you
can take yourself to next levels.
Prerequisites
We assume you have good understanding of the Java programming language. A basic understanding of
relational databases, JDBC and SQL is very helpful.
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Table of Content
Hibernate Tutorial .................................................................... 2
Audience.................................................................................. 2
Prerequisites............................................................................ 2
Copyright & Disclaimer Notice.................................................. 2
ORM Overview......................................................................... 8
Pros and Cons of JDBC...................................................................................8
Why Object Relational Mapping (ORM)?.........................................................8
What is ORM? ..............................................................................................9
Java ORM Frameworks................................................................................10
Hibernate Overview ............................................................... 11
Hibernate Advantages.................................................................................11
Supported Databases..................................................................................12
Supported Technologies..............................................................................12
Hibernate Architecture ........................................................... 13
Configuration Object...................................................................................14
SessionFactory Object .................................................................................14
Session Object............................................................................................15
Transaction Object......................................................................................15
Query Object..............................................................................................15
Criteria Object............................................................................................15
Hibernate Environment .......................................................... 16
Downloading Hibernate:..............................................................................16
Installing Hibernate.....................................................................................17
Hibernate Prerequisites...............................................................................17
Hibernate Configuration ......................................................... 18
Hibernate Properties...................................................................................18
Hibernate with MySQL Database..................................................................19
Hibernate Sessions................................................................ 21
Session Interface Methods ..........................................................................22
Hibernate Persistent Class..................................................... 24
A simple POJO example:..............................................................................24
Hibernate Mapping Files ........................................................ 26
Hibernate Mapping Types ...................................................... 29
Primitive types ...........................................................................................29
Date and time types....................................................................................29
Binary and large object types.......................................................................30
JDK-related types........................................................................................30

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Hibernate Examples............................................................... 31
Create POJO Classes....................................................................................31
Create Database Tables...............................................................................32
Create Mapping Configuration File ...............................................................32
Create Application Class ..............................................................................33
Compilation and Execution ..........................................................................35
Hibernate O/R Mapping ......................................................... 36
Collections Mappings ............................................................................36
Hibernate Set Mappings..............................................................................36
Define RDBMS Tables ................................................................................37
Define POJO Classes...................................................................................37
Define Hibernate Mapping File ..................................................................39
Create Application Class ............................................................................40
Compilation and Execution........................................................................42
Hibernate SortedSet Mappings ....................................................................43
Hibernate List Mappings..............................................................................50
Hibernate Bag Mappings .............................................................................57
Hibernate Map Mappings ............................................................................63
Hibernate SortedMap Mappings ..................................................................69

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Association Mappings ...........................................................................76
Hibernate Many-to-One Mappings ...............................................................76
Hibernate One-to-One Mappings .................................................................83
Hibernate One-to-Many Mappings ...............................................................90
Hibernate Many-to-Many Mappings.............................................................96
Create Application Class ..........................................................................100
Compilation and Execution......................................................................102
Component Mappings...............................................................................103
Hibernate Component Mappings................................................................103
Define RDBMS Tables ..............................................................................103
Define POJO Classes.................................................................................104
Define Hibernate Mapping File ................................................................106
Create Application Class ..........................................................................107
Compilation and Execution......................................................................109
Hibernate Annotations.......................................................... 111
Environment Setup for Hibernate Annotation..............................................111
Annotated Class Example ..........................................................................111
@Entity Annotation ..................................................................................112
@Table Annotation...................................................................................113

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@Id and @GeneratedValue Annotations.....................................................113
@Column Annotation ...............................................................................113
Database Configuration.............................................................................115
Compilation and Execution ........................................................................116
Hibernate Query Language.................................................. 117
FROM Clause............................................................................................117
AS Clause.................................................................................................117
SELECT Clause ..........................................................................................118
WHERE Clause..........................................................................................118
ORDER BY Clause ......................................................................................118
GROUP BY Clause......................................................................................118
Using Named Paramters............................................................................119
UPDATE Clause.........................................................................................119
DELETE Clause ..........................................................................................119
INSERT Clause ..........................................................................................119
Aggregate Methods ..................................................................................119
Pagination using Query .............................................................................120
Hibernate Criteria Queries ................................................... 121
Restrictions with Criteria ...........................................................................121
Pagination using Criteria............................................................................122
Sorting the Results....................................................................................123
Projections & Aggregations........................................................................123
Criteria Queries Example ...........................................................................123
Hibernate Native SQL .......................................................... 128
Scalar queries...........................................................................................128
Entity queries...........................................................................................128
Named SQL queries...................................................................................129
Native SQL Example ..................................................................................129
Hibernate Caching ............................................................... 133
First-level cache........................................................................................133
Second-level cache ...................................................................................134
Query-level cache.....................................................................................134
The Second Level Cache ............................................................................134
Concurrency strategies..............................................................................134
Cache provider .........................................................................................135
The Query-level Cache ..............................................................................137

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Hibernate Batch Processing................................................. 138
Batch Processing Example .........................................................................139
Hibernate Interceptors.......................................................... 143
How to use Interceptors? ..........................................................................144
Create Interceptors...................................................................................144
Create POJO Classes..................................................................................145
Create Database Tables.............................................................................145
Create Mapping Configuration File .............................................................146

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ORM Overview
JDBC stands for Java Database Connectivity and provides a set of Java API for accessing the relational
databases from Java program. These Java APIs enables Java programs to execute SQL statements and interact
with any SQL compliant database.
JDBC provides a flexible architecture to write a database independent application that can run on different
platforms and interact with different DBMS without any modification.
Pros and Cons of JDBC
Pros of JDBC Cons of JDBC
 Clean and simple SQL processing
 Good performance with large data
 Very good for small applications
 Simple syntax so easy to learn
 Complex if it is used in large projects
 Large programming overhead
 No encapsulation
 Hard to implement MVC concept
 Query is DBMS specific
Why Object Relational Mapping (ORM)?
When we work with an object-oriented systems, there's a mismatch between the object model and the relational
database. RDBMSs represent data in a tabular format whereas object-oriented languages, such as Java or C#
represent it as an interconnected graph of objects. Consider the following Java Class with proper constructors and
associated public function:
public class Employee {
private int id;
private String first_name;
private String last_name;
private int salary;
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public Employee() {}
public Employee(String fname, String lname, int salary) {
this.first_name = fname;
this.last_name = lname;
this.salary = salary;
}
public int getId() {
return id;
}
public String getFirstName() {
return first_name;
}
public String getLastName() {
return last_name;
}
public int getSalary() {
return salary;
}
}
Consider above objects need to be stored and retrieved into the following RDBMS table:
create table EMPLOYEE (
id INT NOT NULL auto_increment,
first_name VARCHAR(20) default NULL,
last_name VARCHAR(20) default NULL,
salary INT default NULL,
PRIMARY KEY (id)
);
First problem, what if we need to modify the design of our database after having developed few pages or our
application? Second, Loading and storing objects in a relational database exposes us to the following five
mismatch problems.
Mismatch Description
Granularity
Sometimes you will have an object model which has more classes than the
number of corresponding tables in the database.
Inheritance
RDBMSs do not define anything similar to Inheritance which is a natural paradigm
in object-oriented programming languages.
Identity
A RDBMS defines exactly one notion of 'sameness': the primary key. Java,
however, defines both object identity (a==b) and object equality (a.equals(b)).
Associations
Object-oriented languages represent associations using object references where
as am RDBMS represents an association as a foreign key column.
Navigation The ways you access objects in Java and in a RDBMS are fundamentally different.
The Object-Relational Mapping (ORM) is the solution to handle all the above impedance mismatches.
What is ORM?
ORM stands for Object-Relational Mapping (ORM) is a programming technique for converting data between
relational databases and object oriented programming languages such as Java, C# etc. An ORM system has
following advantages over plain JDBC

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S.N. Advantages
1 Lets business code access objects rather than DB tables.
2 Hides details of SQL queries from OO logic.
3 Based on JDBC 'under the hood'
4 No need to deal with the database implementation.
5 Entities based on business concepts rather than database structure.
6 Transaction management and automatic key generation.
7 Fast development of application.
An ORM solution consists of the following four entities:
S.N. Solutions
1 An API to perform basic CRUD operations on objects of persistent classes.
2 A language or API to specify queries that refer to classes and properties of classes.
3 A configurable facility for specifying mapping metadata.
4
A technique to interact with transactional objects to perform dirty checking, lazy association
fetching, and other optimization functions.
Java ORM Frameworks
There are several persistent frameworks and ORM options in Java. A persistent framework is an ORM service that
stores and retrieves objects into a relational database.
 Enterprise JavaBeans Entity Beans
 Java Data Objects
 Castor
 TopLink
 Spring DAO
 Hibernate
 And many more

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Hibernate Overview
Hibernate is an Object-Relational Mapping(ORM) solution for JAVA and it raised as an open source
persistent framework created by Gavin King in 2001. It is a powerful, high performance Object-Relational
Persistence and Query service for any Java Application.
Hibernate maps Java classes to database tables and from Java data types to SQL data types and relieve the
developer from 95% of common data persistence related programming tasks.
Hibernate sits between traditional Java objects and database server to handle all the work in persisting those
objects based on the appropriate O/R mechanisms and patterns.
Hibernate Advantages
 Hibernate takes care of mapping Java classes to database tables using XML files and without writing
any line of code.
 Provides simple APIs for storing and retrieving Java objects directly to and from the database.
 If there is change in Database or in any table then the only need to change XML file properties.
 Abstract away the unfamiliar SQL types and provide us to work around familiar Java Objects.
 Hibernate does not require an application server to operate.
 Manipulates Complex associations of objects of your database.
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 Minimize database access with smart fetching strategies.
 Provides Simple querying of data.
Supported Databases
Hibernate supports almost all the major RDBMS. Following is list of few of the database engines supported by
Hibernate.
 HSQL Database Engine
 DB2/NT
 MySQL
 PostgreSQL
 FrontBase
 Oracle
 Microsoft SQL Server Database
 Sybase SQL Server
 Informix Dynamic Server
Supported Technologies
Hibernate supports a variety of other technologies, including the following:
 XDoclet Spring
 J2EE
 Eclipse plug-ins
 Maven

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Hibernate Architecture
The Hibernate architecture is layered to keep you isolated from having to know the underlying APIs.
Hibernate makes use of the database and configuration data to provide persistence services (and persistent
objects) to the application.
Following is a very high level view of the Hibernate Application Architecture.
Following is a detailed view of the Hibernate Application Architecture with few important core classes.
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Hibernate uses various existing Java APIs, like JDBC, Java Transaction API(JTA), and Java Naming and
Directory Interface (JNDI). JDBC provides a rudimentary level of abstraction of functionality common to relational
databases, allowing almost any database with a JDBC driver to be supported by Hibernate. JNDI and JTA allow
Hibernate to be integrated with J2EE application servers.
Following section gives brief description of each of the class objects involved in Hibernate Application
Architecture.
Configuration Object
The Configuration object is the first Hibernate object you create in any Hibernate application and usually created
only once during application initialization. It represents a configuration or properties file required by the Hibernate.
The Configuration object provides two keys components:
 Database Connection: This is handled through one or more configuration files supported by Hibernate.
These files are hibernate.properties and hibernate.cfg.xml.
 Class Mapping Setup: This component creates the connection between the Java classes and database
tables.
SessionFactory Object
Configuration object is used to create a SessionFactory object which inturn configures Hibernate for the
application using the supplied configuration file and allows for a Session object to be instantiated. The
SessionFactory is a thread safe object and used by all the threads of an application.

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The SessionFactory is heavyweight object so usually it is created during application start up and kept for later
use. You would need one SessionFactory object per database using a separate configuration file. So if you are
using multiple databases then you would have to create multiple SessionFactory objects.
Session Object
A Session is used to get a physical connection with a database. The Session object is lightweight and designed to
be instantiated each time an interaction is needed with the database. Persistent objects are saved and retrieved
through a Session object.
The session objects should not be kept open for a long time because they are not usually thread safe and they
should be created and destroyed them as needed.
Transaction Object
A Transaction represents a unit of work with the database and most of the RDBMS supports transaction
functionality. Transactions in Hibernate are handled by an underlying transaction manager and transaction (from
JDBC or JTA).
This is an optional object and Hibernate applications may choose not to use this interface, instead managing
transactions in their own application code.
Query Object
Query objects use SQL or Hibernate Query Language (HQL) string to retrieve data from the database and create
objects. A Query instance is used to bind query parameters, limit the number of results returned by the query, and
finally to execute the query.
Criteria Object
Criteria object are used to create and execute object oriented criteria queries to retrieve objects.

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Hibernate Environment
This chapter will explain how to install Hibernate and other associated packages to prepare a develop
environment for the Hibernate applications. We will work with MySQL database to experiment with Hibernate
examples, so make sure you already have setup for MySQL database. For a more detail on MySQL you can
check our MySQL Tutorial.
Downloading Hibernate:
It is assumed that you already have latest version of Java is installed on your machine. Following are the simple
steps to download and install Hibernate on your machine.
 Make a choice whether you want to install Hibernate on Windows, or Unix and then proceed to the next
step to download .zip file for windows and .tz file for Unix.
 Download the latest version of Hibernate from http://www.hibernate.org/downloads.
 At the time of writing this tutorial I downloaded hibernate-distribution-3.6.4.Final and when you unzip
the downloaded file it will give you directory structure as follows.
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Installing Hibernate
Once you downloaded and unzipped the latest version of the Hibernate Installation file, you need to perform
following two simple steps. Make sure you are setting your CLASSPATH variable properly otherwise you will face
problem while compiling your application.
 Now copy all the library files from /lib into your CLASSPATH, and change your classpath variable to
include all the JARs:
 Finally copy hibernate3.jar file into your CLASSPATH. This file lies in the root directory of the
installation and is the primary JAR that Hibernate needs to do its work.
Hibernate Prerequisites
Following is the list of the packages/libraries required by Hibernate and you should install them before starting
with Hibernate. To install these packages you would have to copy library files from /lib into your CLASSPATH,
and change your CLASSPATH variable accordingly.
S.N. Packages/Libraries
1 dom4j - XML parsing www.dom4j.org/
2 Xalan - XSLT Processor http://xml.apache.org/xalan-j/
3 Xerces - The Xerces Java Parser http://xml.apache.org/xerces-j/
4 cglib - Appropriate changes to Java classes at runtime http://cglib.sourceforge.net/
5 log4j - Logging Faremwork http://logging.apache.org/log4j
6 Commons - Logging, Email etc. http://jakarta.apache.org/commons
7 SLF4J - Logging Facade for Java http://www.slf4j.org

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Hibernate Configuration
Hibernate requires to know in advance where to find the mapping information that defines how your Java
classes relate to the database tables. Hibernate also requires a set of configuration settings related to database
and other related parameters. All such information is usually supplied as a standard Java properties file
called hibernate.properties, or as an XML file named hibernate.cfg.xml.
I will consider XML formatted file hibernate.cfg.xml to specify required Hibernate properties in my examples.
Most of the properties take their default values and it is not required to specify them in the property file unless it is
really required. This file is kept in the root directory of your application's classpath.
Hibernate Properties
Following is the list of important properties you would require to configure for a databases in a standalone
situation:
S.N. Properties and Description
1
hibernate.dialect
This property makes Hibernate generate the appropriate SQL for the chosen database.
2
hibernate.connection.driver_class
The JDBC driver class.
3
hibernate.connection.url
The JDBC URL to the database instance.
4
hibernate.connection.username
The database username.
5
hibernate.connection.password
The database password.
6
hibernate.connection.pool_size
Limits the number of connections waiting in the Hibernate database connection pool.
7
hibernate.connection.autocommit
Allows autocommit mode to be used for the JDBC connection.
If you are using a database along with an application server and JNDI then you would have to configure the
following properties:
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S.N. Properties and Description
1
hibernate.connection.datasource
The JNDI name defined in the application server context you are using for the application.
2
hibernate.jndi.class
The InitialContext class for JNDI.
3
hibernate.jndi.<JNDIpropertyname>
Passes any JNDI property you like to the JNDI InitialContext.
4
hibernate.jndi.url
Provides the URL for JNDI.
5
hibernate.connection.username
The database username.
6
hibernate.connection.password
The database password.
Hibernate with MySQL Database
MySQL is one of the most popular open-source database systems available today. Let us
createhibernate.cfg.xml configuration file and place it in the root of your application's classpath. You would have
to make sure that you have testdb database available in your MySQL database and you have a
user test available to access the database.
The XML configuration file must conform to the Hibernate 3 Configuration DTD, which is available from
http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd.
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration SYSTEM
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="hibernate.dialect">
org.hibernate.dialect.MySQLDialect
</property>
<property name="hibernate.connection.driver_class">
com.mysql.jdbc.Driver
</property>

<property name="hibernate.connection.url">
jdbc:mysql://localhost/test
</property>
<property name="hibernate.connection.username">
root
</property>
<property name="hibernate.connection.password">
root123
</property>

<mapping resource="Employee.hbm.xml"/>
</session-factory>
</hibernate-configuration>

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The above configuration file includes <mapping> tags which are related to hibernate-mapping file and we will see
in next chapter what exactly is a hibernate mapping file and how and why do we use it. Following is the list of
various important databases dialect property type:
Database Dialect Property
DB2 org.hibernate.dialect.DB2Dialect
HSQLDB org.hibernate.dialect.HSQLDialect
HypersonicSQL org.hibernate.dialect.HSQLDialect
Informix org.hibernate.dialect.InformixDialect
Ingres org.hibernate.dialect.IngresDialect
Interbase org.hibernate.dialect.InterbaseDialect
Microsoft SQL Server 2000 org.hibernate.dialect.SQLServerDialect
Microsoft SQL Server 2005 org.hibernate.dialect.SQLServer2005Dialect
Microsoft SQL Server 2008 org.hibernate.dialect.SQLServer2008Dialect
MySQL org.hibernate.dialect.MySQLDialect
Oracle (any version) org.hibernate.dialect.OracleDialect
Oracle 11g org.hibernate.dialect.Oracle10gDialect
Oracle 10g org.hibernate.dialect.Oracle10gDialect
Oracle 9i org.hibernate.dialect.Oracle9iDialect
PostgreSQL org.hibernate.dialect.PostgreSQLDialect
Progress org.hibernate.dialect.ProgressDialect
SAP DB org.hibernate.dialect.SAPDBDialect
Sybase org.hibernate.dialect.SybaseDialect
Sybase Anywhere org.hibernate.dialect.SybaseAnywhereDialect
Serial No Class Name Functionality
1 Assert A set of assert methods.
2 TestCase A test case defines the fixture to run multiple tests.
3 TestResult
A TestResult collects the results of executing a
test case.
4 TestSuite A TestSuite is a Composite of Tests.

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Hibernate Sessions
ASession is used to get a physical connection with a database. The Session object is lightweight and
designed to be instantiated each time an interaction is needed with the database. Persistent objects are saved
and retrieved through a Session object.
The session objects should not be kept open for a long time because they are not usually thread safe and they
should be created and destroyed them as needed. The main function of the Session is to offer create, read and
delete operations for instances of mapped entity classes. Instances may exist in one of the following three states
at a given point in time:
 transient: A new instance of a a persistent class which is not associated with a Session and has no
representation in the database and no identifier value is considered transient by Hibernate.
 persistent: You can make a transient instance persistent by associating it with a Session. A persistent
instance has a representation in the database, an identifier value and is associated with a Session.
 detached: Once we close the Hibernate Session, the persistent instance will become a detached
instance.
A Session instance is serializable if its persistent classes are serializable. A typical transaction should use the
following idiom:
Session session = factory.openSession();
Transaction tx = null;
try {
tx = session.beginTransaction();
// do some work
...
tx.commit();
}
catch (Exception e) {
if (tx!=null) tx.rollback();
e.printStackTrace();
}finally {
session.close();
}
If the Session throws an exception, the transaction must be rolled back and the session must be discarded.
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Session Interface Methods
There are number of methods provided by the Session interface but I'm going to list down few important methods
only, which we will use in this tutorial. You can check Hibernate documentation for a complete list of methods
associated with Session and SessionFactory.
S.N. Session Methods and Description
1
Transaction beginTransaction()
Begin a unit of work and return the associated Transaction object.
2
void cancelQuery()
Cancel the execution of the current query.
3
void clear()
Completely clear the session.
4
Connection close()
End the session by releasing the JDBC connection and cleaning up.
5
Criteria createCriteria(Class persistentClass)
Create a new Criteria instance, for the given entity class, or a superclass of an entity class.
6
Criteria createCriteria(String entityName)
Create a new Criteria instance, for the given entity name.
7
Serializable getIdentifier(Object object)
Return the identifier value of the given entity as associated with this session.
8
Query createFilter(Object collection, String queryString)
Create a new instance of Query for the given collection and filter string.
9
Query createQuery(String queryString)
Create a new instance of Query for the given HQL query string.
10
SQLQuery createSQLQuery(String queryString)
Create a new instance of SQLQuery for the given SQL query string.
11
void delete(Object object)
Remove a persistent instance from the datastore.
12
void delete(String entityName, Object object)
Remove a persistent instance from the datastore.
13
Session get(String entityName, Serializable id)
Return the persistent instance of the given named entity with the given identifier, or null if
there is no such persistent instance.
14
SessionFactory getSessionFactory()
Get the session factory which created this session.
15
void refresh(Object object)
Re-read the state of the given instance from the underlying database.
16
Transaction getTransaction()
Get the Transaction instance associated with this session.
17
boolean isConnected()
Check if the session is currently connected.
18
boolean isDirty()
Does this session contain any changes which must be synchronized with the database?

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19
boolean isOpen()
Check if the session is still open.
20
Serializable save(Object object)
Persist the given transient instance, first assigning a generated identifier.
21
void saveOrUpdate(Object object)
Either save(Object) or update(Object) the given instance.
22
void update(Object object)
Update the persistent instance with the identifier of the given detached instance.
23
void update(String entityName, Object object)
Update the persistent instance with the identifier of the given detached instance.

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Hibernate Persistent Class
The entire concept of Hibernate is to take the values from Java class attributes and persist them to a
database table. A mapping document helps Hibernate in determining how to pull the values from the classes and
map them with table and associated fields.
Java classes whose objects or instances will be stored in database tables are called persistent classes in
Hibernate. Hibernate works best if these classes follow some simple rules, also known as the Plain Old Java
Object (POJO) programming model. There are following main rules of persistent classes, however, none of these
rules are hard requirements.
 All Java classes that will be persisted need a default constructor.
 All classes should contain an ID in order to allow easy identification of your objects within Hibernate and
the database. This property maps to the primary key column of a database table.
 All attributes that will be persisted should be declared private and have getXXX and setXXXmethods
defined in the JavaBean style.
 A central feature of Hibernate, proxies, depends upon the persistent class being either non-final, or the
implementation of an interface that declares all public methods.
 All classes that do not extend or implement some specialized classes and interfaces required by the EJB
framework.
The POJO name is used to emphasize that a given object is an ordinary Java Object, not a special object, and in
particular not an Enterprise JavaBean.
A simple POJO example:
Based on the few rules mentioned above we can define a POJO class as follows:
private int id;
private String firstName;
private String lastName;
private int salary;
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this.firstName = fname;
this.lastName = lname;
}
return id;
}
public void setId( int id ) {
this.id = id;
}
return firstName;
}
public void setFirstName( String first_name ) {
this.firstName = first_name;
}
return lastName;
}
public void setLastName( String last_name ) {
this.lastName = last_name;
}
return salary;
}
public void setSalary( int salary ) {
}
}

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Hibernate Mapping Files
An Object/relational mappings are usually defined in an XML document. This mapping file instructs
Hibernate how to map the defined class or classes to the database tables.
Though many Hibernate users choose to write the XML by hand, a number of tools exist to generate the mapping
document. These include XDoclet, Middlegen and AndroMDA for advanced Hibernate users.
Let us consider our previously defined POJO class whose objects will persist in the table defined in next section.
private int id;
private int salary;
}
return id;
}
this.id = id;
}
return firstName;
}
}
return lastName;
}
}
return salary;
}
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8

TUTORIALS POINT
}
}
There would be one table corresponding to each object you are willing to provide persistence. Consider above
objects need to be stored and retrieved into the following RDBMS table:
PRIMARY KEY (id)
);
Based on the two above entities we can define following mapping file which instructs Hibernate how to map the
defined class or classes to the database tables.
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="Employee" table="EMPLOYEE">
<meta attribute="class-description">
This class contains the employee detail.
</meta>
<id name="id" type="int" column="id">
<generator class="native"/>
</id>
<property name="firstName" column="first_name" type="string"/>
<property name="lastName" column="last_name" type="string"/>
<property name="salary" column="salary" type="int"/>
</class>
</hibernate-mapping>
You should save the mapping document in a file with the format <classname>.hbm.xml. We saved our mapping
document in the file Employee.hbm.xml. Let us see little detail about the mapping elements used in the mapping
file:
 The mapping document is an XML document having <hibernate-mapping> as the root element which
contains all the <class> elements.
 The <class> elements are used to define specific mappings from a Java classes to the database tables.
The Java class name is specified using the name attribute of the class element and the database table
name is specified using the table attribute.
 The <meta> element is optional element and can be used to create the class description.
 The <id> element maps the unique ID attribute in class to the primary key of the database table.
The name attribute of the id element refers to the property in the class and the column attribute refers to
the column in the database table. The type attribute holds the hibernate mapping type, this mapping
types will convert from Java to SQL data type.
 The <generator> element within the id element is used to automatically generate the primary key
values. Set the class attribute of the generator element is set to native to let hibernate pick up

TUTORIALS POINT
either identity, sequence or hilo algorithm to create primary key depending upon the capabilities of the
underlying database.
 The <property> element is used to map a Java class property to a column in the database table.
The name attribute of the element refers to the property in the class and the column attribute refers to
There are other attributes and elements available which will be used in a mapping document and I would try to
cover as many as possible while discussing other Hibernate related topics.

TUTORIALS POINT
Hibernate Mapping Types
When you prepare a Hibernate mapping document, we have seen that you map Java data types into
RDBMS data types. The types declared and used in the mapping files are not Java data types; they are not SQL
database types either. These types are called Hibernate mapping types, which can translate from Java to SQL
data types and vice versa.
This chapter lists down all the basic, date and time, large object, and various other built-in mapping types.
Primitive types
Mapping type Java type ANSI SQL Type
integer int or java.lang.Integer INTEGER
long long or java.lang.Long BIGINT
short short or java.lang.Short SMALLINT
float float or java.lang.Float FLOAT
double double or java.lang.Double DOUBLE
big_decimal java.math.BigDecimal NUMERIC
character java.lang.String CHAR(1)
string java.lang.String VARCHAR
byte byte or java.lang.Byte TINYINT
boolean boolean or java.lang.Boolean BIT
yes/no boolean or java.lang.Boolean
CHAR(1) ('Y' or
'N')
true/false boolean or java.lang.Boolean
CHAR(1) ('T' or
'F')
Date and time types
.CHAPTER
9

TUTORIALS POINT
date java.util.Date or java.sql.Date DATE
time java.util.Date or java.sql.Time TIME
timestamp java.util.Date or java.sql.Timestamp TIMESTAMP
calendar java.util.Calendar TIMESTAMP
calendar_date java.util.Calendar DATE
Binary and large object types
binary byte[]
VARBINARY (or
BLOB)
text java.lang.String CLOB
serializable any Java class that implements java.io.Serializable
VARBINARY (or
BLOB)
clob java.sql.Clob CLOB
blob java.sql.Blob BLOB
JDK-related types
class java.lang.Class VARCHAR
locale java.util.Locale VARCHAR
timezone java.util.TimeZone VARCHAR
currency java.util.Currency VARCHAR

TUTORIALS POINT
Hibernate Examples
Let us try an example of using Hibernate to provide Java persistence in a standalone application. We will
go through different steps involved in creating Java Application using Hibernate technology.
Create POJO Classes
The first step in creating an application is to build the Java POJO class or classes, depending on the application
that will be persisted to the database. Let us consider our Employee class with getXXX andsetXXX methods to
make it JavaBeans compliant class.
A POJO (Plain Old Java Object) is a Java object that doesn't extend or implement some specialized classes and
interfaces respectively required by the EJB framework. All normal Java objects are POJO.
When you design a classs to be persisted by Hibernate, it's important to provide JavaBeans compliant code as
well as one attribute which would work as index like id attribute in the Employee class.
private int id;
private int salary;
}
return id;
}
this.id = id;
}
return firstName;
}
}
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10

TUTORIALS POINT
return lastName;
}
}
return salary;
}
}
}
Create Database Tables
Second step would be creating tables in your database. There would be one table corresponding to each object
you are willing to provide persistence. Consider above objects need to be stored and retrieved into the following
RDBMS table:
PRIMARY KEY (id)
);
Create Mapping Configuration File
This step is to create a mapping file that instructs Hibernate how to map the defined class or classes to the
database tables.
<hibernate-mapping>
</meta>
</id>
</class>
document in the file Employee.hbm.xml. Let us see little detail about the mapping document:
contains all the <class> elements.

TUTORIALS POINT
 The <class> elements are used to define specific mappings from a Java classes to the database tables.
The Java class name is specified using the name attribute of the class element and the database table
name is specified using the table attribute.
The name attribute of the id element refers to the property in the class and the column attribute refers to
 The <generator> element within the id element is used to automatically generate the primary key
values. Set the class attribute of the generator element is set to native to let hibernate pick up
either identity, sequence or hilo algorithm to create primary key depending upon the capabilities of the
underlying database.
The name attribute of the element refers to the property in the class and the column attribute refers to
There are other attributes and elements available which will be used in a mapping document and I would try to
cover as many as possible while discussing other Hibernate related topics.
Create Application Class
Finally, we will create our application class with the main() method to run the application. We will use this
application to save few Employee's records and then we will apply CRUD operations on those records.
import java.util.List;
import java.util.Date;
import java.util.Iterator;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class ManageEmployee {
private static SessionFactory factory;
public static void main(String[] args) {
try{
factory = new Configuration().configure().buildSessionFactory();
}catch (Throwable ex) {
System.err.println("Failed to create sessionFactory object." + ex);
throw new ExceptionInInitializerError(ex);
}
ManageEmployee ME = new ManageEmployee();
/* Add few employee records in database */
Integer empID1 = ME.addEmployee("Zara", "Ali", 1000);
Integer empID2 = ME.addEmployee("Daisy", "Das", 5000);
Integer empID3 = ME.addEmployee("John", "Paul", 10000);
/* List down all the employees */
ME.listEmployees();
/* Update employee's records */
ME.updateEmployee(empID1, 5000);

TUTORIALS POINT
/* Delete an employee from the database */
ME.deleteEmployee(empID2);
/* List down new list of the employees */
ME.listEmployees();
}
/* Method to CREATE an employee in the database */
public Integer addEmployee(String fname, String lname, int salary){
Integer employeeID = null;
try{
Employee employee = new Employee(fname, lname, salary);
employeeID = (Integer) session.save(employee);
tx.commit();
}catch (HibernateException e) {
}finally {
session.close();
}
return employeeID;
}
/* Method to READ all the employees */
public void listEmployees( ){
try{
List employees = session.createQuery("FROM Employee").list();
for (Iterator iterator =
employees.iterator(); iterator.hasNext();){
Employee employee = (Employee) iterator.next();
System.out.print("First Name: " + employee.getFirstName());
System.out.print(" Last Name: " + employee.getLastName());
System.out.println(" Salary: " + employee.getSalary());
}
tx.commit();
}finally {
session.close();
}
}
/* Method to UPDATE salary for an employee */
public void updateEmployee(Integer EmployeeID, int salary ){
try{
Employee employee =
(Employee)session.get(Employee.class, EmployeeID);
employee.setSalary( salary );
session.update(employee);
tx.commit();
}finally {
session.close();
}
}
/* Method to DELETE an employee from the records */
public void deleteEmployee(Integer EmployeeID){

TUTORIALS POINT
try{
Employee employee =
session.delete(employee);
tx.commit();
}finally {
session.close();
}
}
}
Compilation and Execution
Here are the steps to compile and run the above mentioned application. Make sure you have set PATH and
CLASSPATH appropriately before proceeding for the compilation and execution.
 Create hibernate.cfg.xml configuration file as explained in configuration chapter.
 Create Employee.hbm.xml mapping file as shown above.
 Create Employee.java source file as shown above and compile it.
 Create ManageEmployee.java source file as shown above and compile it.
 Execute ManageEmployee binary to run the program.
You would get following result, and records would be created in EMPLOYEE table.
$java ManageEmployee
.......VARIOUS LOG MESSAGES WILL DISPLAY HERE........
First Name: Zara Last Name: Ali Salary: 1000
First Name: Daisy Last Name: Das Salary: 5000
First Name: John Last Name: Paul Salary: 10000
If you check your EMPLOYEE table, it should have following records:
mysql> select * from EMPLOYEE;
+----+------------+-----------+--------+
| id | first_name | last_name | salary |
+----+------------+-----------+--------+
| 29 | Zara | Ali | 5000 |
| 31 | John | Paul | 10000 |
+----+------------+-----------+--------+
2 rows in set (0.00 sec
mysql>

TUTORIALS POINT
Hibernate O/R Mapping
So far we have seen very basic O/R mapping using hibernate but there are three most important mapping
topics which we have to learn in detail. These are the mapping of collections, the mapping of associations
between entity classes and Component Mappings.
Collections Mappings
If an entity or class has collection of values for a particular variable, then we can map those values using any one
of the collection interfaces available in java. Hibernate can persist instances ofjava.util.Map, java.util.Set,
java.util.SortedMap, java.util.SortedSet, java.util.List, and any array of persistent entities or values.
Collection type Mapping and Description
java.util.Set This is mapped with a <set> element and initialized with java.util.HashSet
java.util.SortedSet
This is mapped with a <set> element and initialized with java.util.TreeSet.
The sort attribute can be set to either a comparator or natural ordering.
java.util.List This is mapped with a <list> element and initialized with java.util.ArrayList
java.util.Collection
This is mapped with a <bag> or <ibag> element and initialized with
java.util.ArrayList
java.util.Map
This is mapped with a <map> element and initialized with
java.util.HashMap
java.util.SortedMap
This is mapped with a <map> element and initialized with
java.util.TreeMap. The sort attribute can be set to either a comparator or
natural ordering.
Arrays are supported by Hibernate with <primitive-array> for Java primitive value types and <array> for everything
else. However, they are rarely used so I'm not going to discuss them in this tutorial.
If you want to map a user defined collection interfaces which is not directly supported by Hibernate, you need to
tell Hibernate about the semantics of your custom collections which is not very easy and not recommend to be
used.
Hibernate Set Mappings
A Set is a java collection that does not contain any duplicate element. More formally, sets contain no pair of
elements e1 and e2 such that e1.equals(e2), and at most one null element. So objects to be added to a set must
CHAPTER
11

TUTORIALS POINT
implement both the equals() and hashCode() methods so that Java can determine whether any two
elements/objects are identical.
A Set is mapped with a <set> element in the mapping table and initialized with java.util.HashSet. You can use Set
collection in your class when there is no duplicate element required in the collection.
Define RDBMS Tables
Consider a situation where we need to store our employee records in EMPLOYEE table which will have following
structure:
PRIMARY KEY (id)
);
Further, assume each employee can have one or more certificate associated with him/her. So we will store
certificate related information in a separate table which has following structure:
create table CERTIFICATE (
certificate_name VARCHAR(30) default NULL,
employee_id INT default NULL,
PRIMARY KEY (id)
);
There will be one-to-many relationship between EMPLOYEE and CERTIFICATE objects:
Define POJO Classes
Let us implement our POJO class Employee which will be used to persist the objects related to EMPLOYEE table
and having a collection of certificates in Set variable.
import java.util.*;
private int id;
private int salary;
private Set certificates;
}
return id;
}
this.id = id;
}

TUTORIALS POINT
return firstName;
}
}
return lastName;
}
}
return salary;
}
}
public Set getCertificates() {
return certificates;
}
public void setCertificates( Set certificates ) {
this.certificates = certificates;
}
}
Now let us define another POJO class corresponding to CERTIFICATE table so that certificate objects can be
stored and retrieved into the CERTIFICATE table. This class should also implement both the equals() and
hashCode() methods so that Java can determine whether any two elements/objects are identical.
public class Certificate {
private int id;
private String name;
public Certificate() {}
public Certificate(String name) {
this.name = name;
}
return id;
}
this.id = id;
}
public String getName() {
return name;
}
public void setName( String name ) {
this.name = name;
}
public boolean equals(Object obj) {
if (obj == null) return false;
if (!this.getClass().equals(obj.getClass())) return false;
Certificate obj2 = (Certificate)obj;
if((this.id == obj2.getId()) && (this.name.equals(obj2.getName())))
{
return true;
}
return false;
}
public int hashCode() {
int tmp = 0;
tmp = ( id + name ).hashCode();

TUTORIALS POINT
return tmp;
}
}
Define Hibernate Mapping File
Let us develop our mapping file which instructs Hibernate how to map the defined classes to the database tables.
The <set> element will be used to define the rule for Set collection used.
<hibernate-mapping>
</meta>
</id>
<set name="certificates" cascade="all">
<key column="employee_id"/>
<one-to-many class="Certificate"/>
</set>
</class>
<class name="Certificate" table="CERTIFICATE">
This class contains the certificate records.
</meta>
</id>
<property name="name" column="certificate_name" type="string"/>
</class>
document in the file Employee.hbm.xml. You are already familiar with most of the mapping detail but let us see all
the elements of mapping file once again:
contains two <class> elements corresponding to each class.
 The <class> elements are used to define specific mappings from a Java classes to the database tables. The
Java class name is specified using the name attribute of the class element and the database table name is
specified using the table attribute.
The name attribute of the id element refers to the property in the class and the column attribute refers to the
column in the database table. The type attribute holds the hibernate mapping type, this mapping types will
convert from Java to SQL data type.
 The <generator> element within the id element is used to automatically generate the primary key values. Set
the class attribute of the generator element is set to native to let hibernate pick up either identity,
sequence or hilo algorithm to create primary key depending upon the capabilities of the underlying database.

TUTORIALS POINT
The name attribute of the element refers to the property in the class and the column attribute refers to the
 The <set> element is new here and has been introduced to set the relationship between Certificate and
Employee classes. We used the cascade attribute in the <set> element to tell Hibernate to persist the
Certificate objects at the same time as the Employee objects. The nameattribute is set to the
defined Set variable in the parent class, in our case it is certificates. For each set variable, we need to define a
separate set element in the mapping file.
 The <key> element is the column in the CERTIFICATE table that holds the foreign key to the parent object ie.
table EMPLOYEE.
 The <one-to-many> element indicates that one Employee object relates to many Certificate objects and, as
such, the Certificate object must have a Employee parent associated with it. You can use either <one-to-
one>, <many-to-one> or <many-to-many> elements based on your requirement.
application to save few Employee's records alongwith their certificates and then we will apply CRUD operations
on those records.
import java.util.*;
try{
}
/* Let us have a set of certificates for the first employee */
HashSet set1 = new HashSet();
set1.add(new Certificate("MCA"));
set1.add(new Certificate("MBA"));
set1.add(new Certificate("PMP"));
/* Add employee records in the database */
Integer empID1 = ME.addEmployee("Manoj", "Kumar", 4000, set1);
/* Another set of certificates for the second employee */
set2.add(new Certificate("BCA"));
set2.add(new Certificate("BA"));
/* Add another employee record in the database */
Integer empID2 = ME.addEmployee("Dilip", "Kumar", 3000, set2);
ME.listEmployees();
/* Update employee's salary records */

TUTORIALS POINT
ME.listEmployees();
}
/* Method to add an employee record in the database */
public Integer addEmployee(String fname, String lname,
int salary, Set cert){
try{
employee.setCertificates(cert);
tx.commit();
}finally {
session.close();
}
return employeeID;
}
/* Method to list all the employees detail */
try{
for (Iterator iterator1 =
employees.iterator(); iterator1.hasNext();){
Employee employee = (Employee) iterator1.next();
Set certificates = employee.getCertificates();
certificates.iterator(); iterator2.hasNext();){
Certificate certName = (Certificate) iterator2.next();
System.out.println("Certificate: " + certName.getName());
}
}
tx.commit();
}finally {
session.close();
}
}
/* Method to update salary for an employee */
try{
Employee employee =
tx.commit();

TUTORIALS POINT
}finally {
session.close();
}
}
/* Method to delete an employee from the records */
try{
Employee employee =
tx.commit();
}finally {
session.close();
}
}
}
 Create Certificate.java source file as shown above and compile it.
You would get following result on the screen, and same time records would be created in EMPLOYEE and
CERTIFICATE tables.
First Name: Manoj Last Name: Kumar Salary: 4000
Certificate: MBA
Certificate: PMP
Certificate: MCA
First Name: Dilip Last Name: Kumar Salary: 3000
Certificate: BCA
Certificate: BA
Certificate: MBA
Certificate: PMP

TUTORIALS POINT
Certificate: MCA
If you check your EMPLOYEE and CERTIFICATE tables, they should have following records:
mysql> select * from employee;
+----+------------+-----------+--------+
+----+------------+-----------+--------+
| 1 | Manoj | Kumar | 5000 |
+----+------------+-----------+--------+
1 row in set (0.00 sec)
mysql> select * from certificate;
+----+------------------+-------------+
| id | certificate_name | employee_id |
+----+------------------+-------------+
| 1 | MBA | 1 |
| 2 | PMP | 1 |
| 3 | MCA | 1 |
+----+------------------+-------------+
3 rows in set (0.00 sec)
mysql>
Hibernate SortedSet Mappings
A SortedSet is a java collection that does not contain any duplicate element and elements are ordered using their
natural ordering or by a comparator provided.
A SortedSet is mapped with a <set> element in the mapping table and initialized with java.util.TreeSet.
The sort attribute can be set to either a comparator or natural ordering. If we use natural ordering then its iterator
will traverse the set in ascending element order.
Define RDBMS Tables
structure:
PRIMARY KEY (id)
);
PRIMARY KEY (id)
);

TUTORIALS POINT
Define POJO Classes
and having a collection of certificates in SortedSet variable.
import java.util.*;
private int id;
private int salary;
private SortedSet certificates;
}
return id;
}
this.id = id;
}
return firstName;
}
}
return lastName;
}
}
return salary;
}
}
public SortedSet getCertificates() {
}
public void setCertificates( SortedSet certificates ) {
}
}
stored and retrieved into the CERTIFICATE table. This class should also implementComparable interface
and compareTo method which will be used to sort the elements in case you setsort="natural" in your mapping
file (see below mapping file).
public class Certificate implements Comparable <Certificate>{

TUTORIALS POINT
private int id;
this.name = name;
}
return id;
}
this.id = id;
}
return name;
}
this.name = name;
}
public int compareTo(Certificate that){
final int BEFORE = -1;
final int AFTER = 1;
if (that == null) {
return BEFORE;
}
Comparable thisCertificate = this.getName();
Comparable thatCertificate = that.getName();
if(thisCertificate == null) {
return AFTER;
} else if(thatCertificate == null) {
return BEFORE;
} else {
return thisCertificate.compareTo(thatCertificate);
}
}
}
The <set> element will be used to define the rule for SortedSet collection used.
<hibernate-mapping>
</meta>
</id>
<set name="certificates" cascade="all" sort="MyClass">

TUTORIALS POINT
</set>
</class>
</meta>
</id>
</class>
sequence or hilo algorithm to create primary key depending upon the capabilities of the underlying
database.
 The <set> element is used to set the relationship between Certificate and Employee classes. We used
the cascade attribute in the <set> element to tell Hibernate to persist the Certificate objects at the same time
as the Employee objects. The name attribute is set to the definedSortedSet variable in the parent class, in
our case it is certificates. The sort attribute can be set to natural to have natural sorting or it can be set to a
custom class implementingjava.util.Comparator. We have used a class MyClass which implements
java.util.Comparator to reverse the sorting order implemented in Certificate class.
 The <key> element is the column in the CERTIFICATE table that holds the foreign key to the parent object
ie. table EMPLOYEE.
If we use sort="natural" setting then we do not need to create a separate class because Certificate class already
has implemented Comparable interface and hibernate will use compareTo() method defined in Certificate class to
compare certificate names. But we are using a custom comparator classMyClass in our mapping file so we would
have to create this class based on our sorting algorithm. Let us do descending sorting in this class using this
class.
import java.util.Comparator;

TUTORIALS POINT
public class MyClass implements Comparator<Certificate>{
public int compare(Certificate o1, Certificate o2) {
/* To reverse the sorting order, multiple by -1 */
if (o2 == null) {
return BEFORE * -1;
}
Comparable thisCertificate = o1.getName();
Comparable thatCertificate = o2.getName();
return AFTER * 1;
return BEFORE * -1;
} else {
return thisCertificate.compareTo(thatCertificate) * -1;
}
}
}
on those records.
import java.util.*;
try{
}
TreeSet set1 = new TreeSet();
TreeSet set2 = new TreeSet();

TUTORIALS POINT
ME.listEmployees();
ME.listEmployees();
}
int salary, SortedSet cert){
try{
tx.commit();
}finally {
session.close();
}
return employeeID;
}
try{
SortedSet certificates = employee.getCertificates();
}
}
tx.commit();
}finally {
session.close();
}
}
try{

TUTORIALS POINT
Employee employee =
tx.commit();
}finally {
session.close();
}
}
try{
Employee employee =
tx.commit();
}finally {
session.close();
}
}
}
 Create MyClass.java source file as shown above and compile it.
CERTIFICATE tables. You can see certificates has been sorted in reverse order. You can try by changing your
mapping file, simply set sort="natural" and execute your program and compare the results.
Certificate: PMP
Certificate: MCA

TUTORIALS POINT
Certificate: MBA
Certificate: BCA
Certificate: BA
Certificate: PMP
Certificate: MCA
Certificate: MBA
+----+------------+-----------+--------+
+----+------------+-----------+--------+
| 1 | Manoj | Kumar | 5000 |
+----+------------+-----------+--------+
+----+------------------+-------------+
+----+------------------+-------------+
| 1 | MBA | 1 |
| 2 | PMP | 1 |
| 3 | MCA | 1 |
+----+------------------+-------------+
mysql>
Hibernate List Mappings
A List is a java collection that stores elements in sequence and allow duplicate elements. The user of this
interface has precise control over where in the list each element is inserted. The user can access elements by
their integer index, and search for elements in the list. More formally, lists typically allow pairs of elements e1 and
e2 such that e1.equals(e2), and they typically allow multiple null elements if they allow null elements at all.
A List is mapped with a <list> element in the mapping table and initialized with java.util.ArrayList.
Define RDBMS Tables
structure:
PRIMARY KEY (id)
);

TUTORIALS POINT
Further, assume each employee can have one or more certificate associated with him/her. A List collection
mapping needs an index column in the collection table. The index column defines the position of the element in
the collection. So we will store certificate related information in a separate table which has following structure:
idx INT default NULL,
PRIMARY KEY (id)
);
There will be one-to-many relationship between EMPLOYEE and CERTIFICATE objects.
Define POJO Classes
Let us implement a POJO class Employee which will be used to persist the objects related to EMPLOYEE table
and having a collection of certificates in List variable.
import java.util.*;
private int id;
private int salary;
private List certificates;
}
return id;
}
this.id = id;
}
return firstName;
}
}
return lastName;
}
}
return salary;
}
}
public List getCertificates() {

TUTORIALS POINT
}
public void setCertificates( List certificates ) {
}
}
We need to define another POJO class corresponding to CERTIFICATE table so that certificate objects can be
stored and retrieved into the CERTIFICATE table.
public class Certificate{
private int id;
this.name = name;
}
return id;
}
this.id = id;
}
return name;
}
this.name = name;
}
}
The <list> element will be used to define the rule for List collection used. The index of list is always of type integer
and is mapped using the <list-index> element.
<hibernate-mapping>
</meta>
</id>
<list name="certificates" cascade="all">
<list-index column="idx"/>
</list>
</class>

TUTORIALS POINT
</meta>
</id>
</class>
 The <list> element is used to set the relationship between Certificate and Employee classes. We used
the cascade attribute in the <list> element to tell Hibernate to persist the Certificate objects at the same time
as the Employee objects. The name attribute is set to the defined Listvariable in the parent class, in our case
it is certificates.
table EMPLOYEE.
 The <list-index> element is used to keep the position of the element and map with the index column in the
collection table. The index of the persistent list starts at zero. You could change this, for example, with <list-
index base="1".../> in your mapping.
one>, <many-to-one> or <many-to-many> elements based on your requirement. If we changed this example
to use a many-to-many relationship, we would need an association table to map between the parent and the
child objects.
on those records.
import java.util.*;

TUTORIALS POINT
try{
}
ArrayList set1 = new ArrayList();
ME.listEmployees();
ME.listEmployees();
}
int salary, ArrayList cert){
try{
tx.commit();
}finally {
session.close();
}
return employeeID;
}

TUTORIALS POINT
try{
List certificates = employee.getCertificates();
}
}
tx.commit();
}finally {
session.close();
}
}
try{
Employee employee =
tx.commit();
}finally {
session.close();
}
}
try{
Employee employee =
tx.commit();
}finally {
session.close();
}
}
}

TUTORIALS POINT
Certificate: MCA
Certificate: MBA
Certificate: PMP
Certificate: BCA
Certificate: BA
Certificate: MCA
Certificate: MBA
Certificate: PMP
+----+------------+-----------+--------+
+----+------------+-----------+--------+
| 51 | Manoj | Kumar | 5000 |
+----+------------+-----------+--------+
mysql> select * from CERTIFICATE;
+----+------------------+------+-------------+
| id | certificate_name | idx | employee_id |
+----+------------------+------+-------------+
| 6 | MCA | 0 | 51 |
| 7 | MBA | 1 | 51 |
| 8 | PMP | 2 | 51 |
+----+------------------+------+-------------+
mysql>
Alternatively, you could map a Java array instead of a list. A array mapping is virtually identical to the previous
example, except with different element and attribute names (<array> and <array-index>). However, for reasons
explained earlier, Hibernate applications rarely use arrays.

TUTORIALS POINT
Hibernate Bag Mappings
A Bag is a java collection that stores elements without caring about the sequencing but allow duplicate elements
in the list. A bag is a random grouping of the objects in the list.
A Collection is mapped with a <bag> element in the mapping table and initialized with java.util.ArrayList.
Define RDBMS Tables
structure:
PRIMARY KEY (id)
);
Further, assume each employee can have one or more certificate associated with him/her. We will store
PRIMARY KEY (id)
);
Define POJO Classes
import java.util.*;
private int id;
private int salary;
private Collection certificates;
}
return id;
}
this.id = id;
}

TUTORIALS POINT
return firstName;
}
}
return lastName;
}
}
return salary;
}
}
public Collection getCertificates() {
}
public void setCertificates( Collection certificates ) {
}
}
private int id;
this.name = name;
}
return id;
}
this.id = id;
}
return name;
}
this.name = name;
}
}
The <bag> element will be used to define the rule for the Collection used.

TUTORIALS POINT
<hibernate-mapping>
</meta>
</id>
<bag name="certificates" cascade="all">
</bag>
</class>
</meta>
</id>
</class>
database.
 The <bag> element is used to set the relationship between Certificate and Employee classes. We used
the cascade attribute in the <bag> element to tell Hibernate to persist the Certificate objects at the same time
as the Employee objects. The name attribute is set to the definedCollection variable in the parent class, in
our case it is certificates.
ie. table EMPLOYEE.

TUTORIALS POINT
on those records.
import java.util.*;
try{
}
ME.listEmployees();
ME.listEmployees();
}
int salary, ArrayList cert){
try{

TUTORIALS POINT
tx.commit();
}finally {
session.close();
}
return employeeID;
}
try{
Collection certificates = employee.getCertificates();
}
}
tx.commit();
}finally {
session.close();
}
}
try{
Employee employee =
tx.commit();
}finally {
session.close();
}
}
try{
Employee employee =
tx.commit();

TUTORIALS POINT
}finally {
session.close();
}
}
}
Certificate: MCA
Certificate: MBA
Certificate: PMP
Certificate: BCA
Certificate: BA
Certificate: MCA
Certificate: MBA
Certificate: PMP
+----+------------+-----------+--------+
+----+------------+-----------+--------+
| 53 | Manoj | Kumar | 5000 |
+----+------------+-----------+--------+
+----+------------------+-------------+
+----+------------------+-------------+

TUTORIALS POINT
| 11 | MCA | 53 |
| 12 | MBA | 53 |
| 13 | PMP | 53 |
+----+------------------+-------------+
mysql>
Hibernate Map Mappings
A Map is a java collection that stores elements in key-value pairs and does not allow duplicate elements in the
list. The Map interface provides three collection views, which allow a map's contents to be viewed as a set of
keys, collection of values, or set of key-value mappings.
A Map is mapped with a <map> element in the mapping table and an unordered map can be initialized with
java.util.HashMap.
Define RDBMS Tables
structure:
PRIMARY KEY (id)
);
certificate_type VARCHAR(40) default NULL,
PRIMARY KEY (id)
);
Define POJO Classes
import java.util.*;
private int id;

TUTORIALS POINT
private int salary;
private Map certificates;
}
return id;
}
this.id = id;
}
return firstName;
}
}
return lastName;
}
}
return salary;
}
}
public Map getCertificates() {
}
public void setCertificates( Map certificates ) {
}
}
private int id;
this.name = name;
}
return id;
}
this.id = id;
}

TUTORIALS POINT
return name;
}
this.name = name;
}
}
The <map> element will be used to define the rule for the Map used.
<hibernate-mapping>
</meta>
</id>
<map name="certificates" cascade="all">
<index column="certificate_type" type="string"/>
</map>
</class>
</meta>
</id>
</class>

TUTORIALS POINT
 The <map> element is used to set the relationship between Certificate and Employee classes. We used
the cascade attribute in the <map> element to tell Hibernate to persist the Certificate objects at the same time
as the Employee objects. The name attribute is set to the defined Mapvariable in the parent class, in our case
it is certificates.
 The <index> element is used to represents the key parts of the key/value map pair. The key will be stored in
the column certificate_type using a type of string.
table EMPLOYEE.
application to save an Employee record alongwith a list of certificates and then we will apply CRUD operations on
that record.
import java.util.*;
try{
}
HashMap set = new HashMap();
set.put("ComputerScience", new Certificate("MCA"));
set.put("BusinessManagement", new Certificate("MBA"));
set.put("ProjectManagement", new Certificate("PMP"));
Integer empID = ME.addEmployee("Manoj", "Kumar", 4000, set);
ME.listEmployees();
ME.updateEmployee(empID, 5000);
ME.listEmployees();
}

TUTORIALS POINT
int salary, HashMap cert){
try{
tx.commit();
}finally {
session.close();
}
return employeeID;
}
try{
Map ec = employee.getCertificates();
System.out.println("Certificate: " +
(((Certificate)ec.get("ComputerScience")).getName()));
(((Certificate)ec.get("BusinessManagement")).getName()));
(((Certificate)ec.get("ProjectManagement")).getName()));
}
tx.commit();
}finally {
session.close();
}
}
try{
Employee employee =
tx.commit();
}finally {
session.close();
}

TUTORIALS POINT
}
try{
Employee employee =
tx.commit();
}finally {
session.close();
}
}
}
CERTIFICATE tables.
Certificate: MCA
Certificate: MBA
Certificate: PMP
Certificate: MCA
Certificate: MBA
Certificate: PMP
+----+------------+-----------+--------+

TUTORIALS POINT
+----+------------+-----------+--------+
| 60 | Manoj | Kumar | 5000 |
+----+------------+-----------+--------+
mysql>select * from CERTIFICATE;
+----+--------------------+------------------+-------------+
| id | certificate_type | certificate_name | employee_id |
+----+--------------------+------------------+-------------+
| 16 | ProjectManagement | PMP | 60 |
| 17 | BusinessManagement | MBA | 60 |
| 18 | ComputerScience | MCA | 60 |
+----+--------------------+------------------+-------------+
mysql>
Hibernate SortedMap Mappings
A SortedMap is a similar java collection as Map that stores elements in key-value pairs and provides a total
ordering on its keys. Duplicate elements are not allowed in the map. The map is ordered according to the natural
ordering of its keys, or by a Comparator typically provided at sorted map creation time.
A SortedMap is mapped with a <map> element in the mapping table and an ordered map can be initialized with
java.util.TreeMap.
Define RDBMS Tables
structure:
PRIMARY KEY (id)
);
certificate_type VARCHAR(40) default NULL,
PRIMARY KEY (id)
);

TUTORIALS POINT
Define POJO Classes
import java.util.*;
private int id;
private int salary;
private SortedMap certificates;
}
return id;
}
this.id = id;
}
return firstName;
}
}
return lastName;
}
}
return salary;
}
}
public SortedMap getCertificates() {
}
public void setCertificates( SortedMap certificates ) {
}
}
stored and retrieved into the CERTIFICATE table. This class should also implement Comparable interface and
compareTo method which will be used to sort the key elements of the SortedMap in case you set sort="natural" in
your mapping file (see below mapping file).

TUTORIALS POINT
public class Certificate implements Comparable <String>{
private int id;
this.name = name;
}
return id;
}
this.id = id;
}
return name;
}
this.name = name;
}
public int compareTo(String that){
if (that == null) {
return BEFORE;
}
Comparable thisCertificate = this;
Comparable thatCertificate = that;
return AFTER;
return BEFORE;
} else {
return thisCertificate.compareTo(thatCertificate);
}
}
}
The <map> element will be used to define the rule for the Map used.
<hibernate-mapping>
</meta>
</id>
<map name="certificates" cascade="all" sort="MyClass">
<index column="certificate_type" type="string"/>

TUTORIALS POINT
</map>
</class>
</meta>
</id>
</class>
 The <map> element is used to set the relationship between Certificate and Employee classes. We used
the cascade attribute in the <map> element to tell Hibernate to persist the Certificate objects at the same time
as the Employee objects. The name attribute is set to the definedSortedMap variable in the parent class, in
our case it is certificates. The sort attribute can be set to natural to have natural sorting or it can be set to a
custom class implementingjava.util.Comparator. We have used a class MyClass which implements
java.util.Comparator to reverse the sorting order implemented in Certificate class.
 The <index> element is used to represents the key parts of the key/value map pair. The key will be stored in
the column certificate_type using a type of string.
table EMPLOYEE.
If we use sort="natural" setting then we do not need to create a separate class because Certificate class already
has implemented Comparable interface and hibernate will use compareTo() method defined in Certificate class to
compare SortedMap keys. But we are using a custom comparator classMyClass in our mapping file so we would
have to create this class based on our sorting algorithm. Let us do descending sorting of the keys available in the
map.
import java.util.Comparator;

TUTORIALS POINT
public class MyClass implements Comparator <String>{
public int compare(String o1, String o2) {
/* To reverse the sorting order, multiple by -1 */
if (o2 == null) {
return BEFORE * -1;
}
Comparable thisCertificate = o1;
Comparable thatCertificate = o2;
return AFTER * 1;
return BEFORE * -1;
} else {
return thisCertificate.compareTo(thatCertificate) * -1;
}
}
}
Finally, we will create our application class with the main() method to run the application. We will use this application to save few
Employee's records alongwith their certificates and then we will apply CRUD operations on those records.
import java.util.*;
try{
}
TreeMap set1 = new TreeMap();
set1.put("ComputerScience", new Certificate("MCA"));
set1.put("BusinessManagement", new Certificate("MBA"));
set1.put("ProjectManagement", new Certificate("PMP"));
TreeMap set2 = new TreeMap();
set2.put("ComputerScience", new Certificate("MCA"));
set2.put("BusinessManagement", new Certificate("MBA"));
ME.listEmployees();

TUTORIALS POINT
ME.listEmployees();
}
int salary, TreeMap cert){
try{
tx.commit();
}finally {
session.close();
}
return employeeID;
}
try{
SortedMap<String, Certificate> map =
employee.getCertificates();
for(Map.Entry<String,Certificate> entry : map.entrySet()){
System.out.print("tCertificate Type: " + entry.getKey());
System.out.println(", Name: " +
(entry.getValue()).getName());
}
}
tx.commit();
}finally {
session.close();
}
}
try{
Employee employee =

TUTORIALS POINT
tx.commit();
}finally {
session.close();
}
}
try{
Employee employee =
tx.commit();
}finally {
session.close();
}
}
}
 Create MyClass.java source file as shown above and compile it.
CERTIFICATE tables. You can see certificates type has been sorted in reverse order. You can try by changing
your mapping file, simply set sort="natural" and execute your program and compare the results.
Certificate Type: ProjectManagement, Name: PMP
Certificate Type: ComputerScience, Name: MCA
Certificate Type: BusinessManagement, Name: MBA

TUTORIALS POINT
Certificate Type: ProjectManagement, Name: PMP
+----+------------+-----------+--------+
+----+------------+-----------+--------+
| 74 | Manoj | Kumar | 5000 |
+----+------------+-----------+--------+
+----+--------------------+------------------+-------------+
| id | certificate_type | certificate_name | employee_id |
+----+--------------------+------------------+-------------+
| 52 | BusinessManagement | MBA | 74 |
| 53 | ComputerScience | MCA | 74 |
| 54 | ProjectManagement | PMP | 74 |
+----+--------------------+------------------+-------------+
mysql>
Association Mappings
The mapping of associations between entity classes and the relationships between tables is the soul of ORM.
Following are the four ways in which the cardinality of the relationship between the objects can be expressed. An
association mapping can be unidirectional as well as bidirectional.
Mapping type Description
Many-to-One Mapping many-to-one relationship using Hibernate
One-to-One Mapping one-to-one relationship using Hibernate
One-to-Many Mapping one-to-many relationship using Hibernate
Many-to-Many Mapping many-to-many relationship using Hibernate
Hibernate Many-to-One Mappings
A many-to-one association is the most common kind of association where an Object can be associated with
multiple objects. For example a same address object can be associated with multiple employee objects.
Define RDBMS Tables
structure:

TUTORIALS POINT
address INT NOT NULL,
PRIMARY KEY (id)
);
Further, many employee can have same address, so this association can be presented using many-to-one
association. We will store address related information in a separate table which has following structure:
create table ADDRESS (
street_name VARCHAR(40) default NULL,
city_name VARCHAR(40) default NULL,
state_name VARCHAR(40) default NULL,
zipcode VARCHAR(10) default NULL,
PRIMARY KEY (id)
);
Create both the RBDMS tables and keep them ready for the next implementation.
Define POJO Classes
and having a variable of Address type.
import java.util.*;
public class Employee{
private int id;
private int salary;
private Address address;
public Employee(String fname, String lname,
int salary, Address address ) {
this.address = address;
}
return id;
}
this.id = id;
}
return firstName;
}
}
return lastName;

TUTORIALS POINT
}
}
return salary;
}
}
public Address getAddress() {
return address;
}
public void setAddress( Address address ) {
}
}
We need to define another POJO class corresponding to ADDRESS table so that address objects can be stored
and retrieved into the ADDRESS table.
import java.util.*;
public class Address{
private int id;
private String street;
private String city;
private String state;
private String zipcode;
public Address() {}
public Address(String street, String city,
String state, String zipcode) {
this.street = street;
this.city = city;
this.state = state;
this.zipcode = zipcode;
}
return id;
}
this.id = id;
}
public String getStreet() {
return street;
}
public void setStreet( String street ) {
}
public String getCity() {
return city;
}
public void setCity( String city ) {
this.city = city;
}
public String getState() {
return state;
}

TUTORIALS POINT
public void setState( String state ) {
this.state = state;
}
public String getZipcode() {
return zipcode;
}
public void setZipcode( String zipcode ) {
}
}
Let us develop our mapping files which instructs Hibernate how to map the defined classes to the database
tables. The <many-to-one> element will be used to define the rule to establish a many-to-one relationship
between EMPLOYEE and ADDRESS entities.
<hibernate-mapping>
</meta>
</id>
<many-to-one name="address" column="address"
class="Address" not-null="true"/>
</class>
<class name="Address" table="ADDRESS">
This class contains the address detail.
</meta>
</id>
<property name="street" column="street_name" type="string"/>
<property name="city" column="city_name" type="string"/>
<property name="state" column="state_name" type="string"/>
<property name="zipcode" column="zipcode" type="string"/>
</class>

TUTORIALS POINT
database.
 The <many-to-one> element is used to set the relationship between EMPLOYEE and ADDRESS entities.
The name attribute is set to the defined variable in the parent class, in our case it isaddress.
The column attribute is used to set the column name in the parent table EMPLOYEE.
on those records.
import java.util.*;
try{
}
/* Let us have one address object */
Address address = ME.addAddress("Kondapur","Hyderabad","AP","532");
Integer empID1 = ME.addEmployee("Manoj", "Kumar", 4000, address);
Integer empID2 = ME.addEmployee("Dilip", "Kumar", 3000, address);
ME.listEmployees();
ME.listEmployees();

TUTORIALS POINT
}
/* Method to add an address record in the database */
public Address addAddress(String street, String city,
Integer addressID = null;
Address address = null;
try{
address = new Address(street, city, state, zipcode);
addressID = (Integer) session.save(address);
tx.commit();
}finally {
session.close();
}
return address;
}
int salary, Address address){
try{
Employee employee = new Employee(fname, lname, salary, address);
tx.commit();
}finally {
session.close();
}
return employeeID;
}
try{
Address add = employee.getAddress();
System.out.println("Address ");
System.out.println("tStreet: " + add.getStreet());
System.out.println("tCity: " + add.getCity());
System.out.println("tState: " + add.getState());
System.out.println("tZipcode: " + add.getZipcode());
}
tx.commit();
}finally {

TUTORIALS POINT
session.close();
}
}
try{
Employee employee =
tx.commit();
}finally {
session.close();
}
}
try{
Employee employee =
tx.commit();
}finally {
session.close();
}
}
}
 Create Address.java source file as shown above and compile it.
ADDRESS tables.

TUTORIALS POINT
address INT NOT NULL,
PRIMARY KEY (id)
);
Further, assuming that an address can be associated a single employee only, so this association can be
presented using one-to-one association. We will store address related information in a separate table which has
following structure:
create table ADDRESS (
PRIMARY KEY (id)
);
Create both the RBDMS tables and keep them ready for the next implementation.
Define POJO Classes
and having a variable of Address type.
import java.util.*;
public class Employee{
private int id;
private int salary;
}
return id;
}
this.id = id;
}
return firstName;
}
}
return lastName;
}
}

TUTORIALS POINT
return salary;
}
}
return address;
}
}
}
We need to define another POJO class corresponding to ADDRESS table so that address objects can be stored
and retrieved into the ADDRESS table.
import java.util.*;
private int id;
public Address() {}
this.city = city;
this.state = state;
}
return id;
}
this.id = id;
}
return street;
}
}
return city;
}
this.city = city;
}
return state;
}
this.state = state;
}

TUTORIALS POINT
return zipcode;
}
}
}
Let us develop our mapping files which instructs Hibernate how to map the defined classes to the database
tables. The <many-to-one> element will be used to define the rule to establish a one-to-one relationship between
EMPLOYEE and ADDRESS entities but column attribute will be set to uniqueconstraint and rest of the mapping
file will remain as it was in case of many-to-one association.
<hibernate-mapping>
</meta>
</id>
<many-to-one name="address" column="address" unique="true"
class="Address" not-null="true"/>
</class>
<class name="Address" table="ADDRESS">
This class contains the address detail.
</meta>
</id>
</class>

TUTORIALS POINT
 The <many-to-one> element is used to set the relationship between EMPLOYEE and ADDRESS entities.
The name attribute is set to the defined variable in the parent class, in our case it isaddress.
The column attribute is used to set the column name in the parent table EMPLOYEE which is set
to unique so that only one Employee object can be associated with an address object.
on those records.
import java.util.*;
try{
}
Address address1 = ME.addAddress("Kondapur","Hyderabad","AP","532");
Integer empID1 = ME.addEmployee("Manoj", "Kumar", 4000, address1);
/* Let us have another address object */
Address address2 = ME.addAddress("Saharanpur","Ambehta","UP","111");
Integer empID2 = ME.addEmployee("Dilip", "Kumar", 3000, address2);
ME.listEmployees();
ME.listEmployees();
}

TUTORIALS POINT
try{
tx.commit();
}finally {
session.close();
}
return address;
}
try{
tx.commit();
}finally {
session.close();
}
return employeeID;
}
try{
}
tx.commit();
}finally {
session.close();
}
}

TUTORIALS POINT
try{
Employee employee =
tx.commit();
}finally {
session.close();
}
}
}
 Create Address.java source file as shown above and compile it.
ADDRESS tables.
Address
Street: Kondapur
City: Hyderabad
State: AP
Zipcode: 532
Address
Street: Saharanpur
City: Ambehta
State: UP
Zipcode: 111
Address
Street: Kondapur
City: Hyderabad
State: AP
Zipcode: 532
Address
Street: Saharanpur

TUTORIALS POINT
City: Ambehta
State: UP
Zipcode: 111
+----+------------+-----------+--------+---------+
| id | first_name | last_name | salary | address |
+----+------------+-----------+--------+---------+
| 7 | Manoj | Kumar | 5000 | 5 |
| 8 | Dilip | Kumar | 3000 | 6 |
+----+------------+-----------+--------+---------+
mysql> select * from ADDRESS;
+----+-------------+-----------+------------+---------+
| id | street_name | city_name | state_name | zipcode |
+----+-------------+-----------+------------+---------+
| 5 | Kondapur | Hyderabad | AP | 532 |
| 6 | Saharanpur | Ambehta | UP | 111 |
+----+-------------+-----------+------------+---------+
mysql>
Hibernate One-to-Many Mappings
A One-to-Many mapping can be implemented using a Set java collection that does not contain any duplicate
element. We already have seen how to map Set collection in hibernate, so if you already learned Set mapping
then you are all set to go with one-to-many mapping.
Define RDBMS Tables
structure:
PRIMARY KEY (id)
);

TUTORIALS POINT
PRIMARY KEY (id)
);
Define POJO Classes
import java.util.*;
private int id;
private int salary;
}
return id;
}
this.id = id;
}
return firstName;
}
}
return lastName;
}
}
return salary;
}
}
}
}
}
stored and retrieved into the CERTIFICATE table. This class should also implement both the equals() and
hashCode() methods so that Java can determine whether any two elements/objects are identical.

TUTORIALS POINT
private int id;
this.name = name;
}
return id;
}
this.id = id;
}
return name;
}
this.name = name;
}
{
return true;
}
return false;
}
int tmp = 0;
return tmp;
}
}
<hibernate-mapping>
</meta>
</id>
<set name="certificates" cascade="all">
</set>
</class>

TUTORIALS POINT
</meta>
</id>
</class>
database.
 The <set> element sets the relationship between Certificate and Employee classes. We used
the cascade attribute in the <set> element to tell Hibernate to persist the Certificate objects at the same time
as the Employee objects. The name attribute is set to the defined Set variable in the parent class, in our case
it is certificates. For each set variable, we need to define a separate set element in the mapping file.
ie. table EMPLOYEE.
 The <one-to-many> element indicates that one Employee object relates to many Certificate objects.
on those records.
import java.util.*;
try{

TUTORIALS POINT
}
ME.listEmployees();
ME.listEmployees();
}
try{
tx.commit();
}finally {
session.close();
}
return employeeID;
}
try{

TUTORIALS POINT
}
}
tx.commit();
}finally {
session.close();
}
}
try{
Employee employee =
tx.commit();
}finally {
session.close();
}
}
try{
Employee employee =
tx.commit();
}finally {
session.close();
}
}
}

TUTORIALS POINT
CERTIFICATE tables.
Certificate: MBA
Certificate: PMP
Certificate: MCA
Certificate: BCA
Certificate: BA
Certificate: MBA
Certificate: PMP
Certificate: MCA
+----+------------+-----------+--------+
+----+------------+-----------+--------+
| 1 | Manoj | Kumar | 5000 |
+----+------------+-----------+--------+
+----+------------------+-------------+
+----+------------------+-------------+
| 1 | MBA | 1 |
| 2 | PMP | 1 |
| 3 | MCA | 1 |
+----+------------------+-------------+
mysql>
Hibernate Many-to-Many Mappings
A Many-to-Many mapping can be implemented using a Set java collection that does not contain any duplicate
element. We already have seen how to map Set collection in hibernate, so if you already learned Set mapping
then you are all set to go with many-to-many mapping.

TUTORIALS POINT
Define RDBMS Tables
structure:
PRIMARY KEY (id)
);
Further, assume each employee can have one or more certificate associated with him/her and a similar certificate
can be associated with more than one employee. We will store certificate related information in a separate table
which has following structure:
PRIMARY KEY (id)
);
Now to implement many-to-many relationship between EMPLOYEE and CERTIFICATE objects, we would have
to introduce one more intermediate table having Employee ID and Certificate ID as follows:
create table EMP_CERT (
employee_id INT NOT NULL,
certificate_id INT NOT NULL,
PRIMARY KEY (employee_id,certificate_id)
);
Define POJO Classes
import java.util.*;
private int id;
private int salary;
}
return id;
}
this.id = id;
}
return firstName;
}

TUTORIALS POINT
}
return lastName;
}
}
return salary;
}
}
}
}
}
Now let us define another POJO class corresponding to CERTIFICATE table so that certificate objects can be stored and
retrieved into the CERTIFICATE table. This class should also implement both the equals() and hashCode() methods so that
Java can determine whether any two elements/objects are identical.
private int id;
this.name = name;
}
return id;
}
this.id = id;
}
return name;
}
this.name = name;
}
{
return true;
}
return false;
}
int tmp = 0;
return tmp;
}
}

TUTORIALS POINT
The <set> element will be used to define the rule for many-to-many relationship.
<hibernate-mapping>
</meta>
</id>
<set name="certificates" cascade="save-update" table="EMP_CERT">
<many-to-many column="certificate_id" class="Certificate"/>
</set>
</class>
</meta>
</id>
</class>
 The <set> element sets the relationship between Certificate and Employee classes. We setcascade attribute
to save-update to tell Hibernate to persist the Certificate objects for SAVE i.e. CREATE and UPDATE

TUTORIALS POINT
operations at the same time as the Employee objects. The name attribute is set to the defined Set variable in
the parent class, in our case it is certificates. For each set variable, we need to define a separate set element
in the mapping file. Here we used nameattribute to set the intermediate table name to EMP_CERT.
 The <key> element is the column in the EMP_CERT table that holds the foreign key to the parent object ie.
table EMPLOYEE and links to the certification_id in the CERTIFICATE table.
 The <many-to-many> element indicates that one Employee object relates to many Certificate objects and
column attributes are used to link intermediate EMP_CERT.
on those records.
import java.util.*;
try{
}
HashSet certificates = new HashSet();
certificates.add(new Certificate("MCA"));
certificates.add(new Certificate("MBA"));
certificates.add(new Certificate("PMP"));
Integer empID1 = ME.addEmployee("Manoj", "Kumar", 4000, certificates);
Integer empID2 = ME.addEmployee("Dilip", "Kumar", 3000, certificates);
ME.listEmployees();
ME.listEmployees();
}

TUTORIALS POINT
try{
tx.commit();
}finally {
session.close();
}
return employeeID;
}
try{
}
}
tx.commit();
}finally {
session.close();
}
}
try{
Employee employee =
tx.commit();
}finally {
session.close();
}
}
try{
Employee employee =

TUTORIALS POINT
tx.commit();
}finally {
session.close();
}
}
}
You would get following result on the screen, and same time records would be created in EMPLOYEE,
EMP_CERT and CERTIFICATE tables.
Certificate: MBA
Certificate: PMP
Certificate: MCA
Certificate: MBA
Certificate: PMP
Certificate: MCA
Certificate: MBA
Certificate: PMP
Certificate: MCA
If you check your EMPLOYEE, EMP_CERT and CERTIFICATE tables, they should have following records:
+----+------------+-----------+--------+
+----+------------+-----------+--------+
| 22 | Manoj | Kumar | 5000 |
+----+------------+-----------+--------+

TUTORIALS POINT
+----+------------------+
| id | certificate_name |
+----+------------------+
| 4 | MBA |
| 5 | PMP |
| 6 | MCA |
+----+------------------+
mysql> select * from EMP_CERT;
+-------------+----------------+
| employee_id | certificate_id |
+-------------+----------------+
| 22 | 4 |
| 22 | 5 |
| 22 | 6 |
+-------------+----------------+
mysql>
Component Mappings
It is very much possible that an Entity class can have a reference to another class as a member variable. If the
referred class does not have it's own life cycle and completely depends on the life cycle of the owning entity class,
then the referred class hence therefore is called as the Component class.
The mapping of Collection of Components is also possible in a similar way just as the mapping of regular
Collections with minor configuration differences. We will see these two mappings in detail with examples.
Mapping type Description
Component Mappings
Mapping for a class having a reference to another class as a member
variable.
Hibernate Component Mappings
A Component mapping is a mapping for a class having a reference to another class as a member variable. We
have seen such mapping while having two tables and using <set> element in the mapping file. Now we will use
<component> element in the mapping file and a single table would be used to keep the attributes contained inside
the class variable.
Define RDBMS Tables
structure:
PRIMARY KEY (id)

TUTORIALS POINT
);
Further, assume each employe will have an address, so let us add address specific fields in the same table as
follows:
PRIMARY KEY (id)
);
Define POJO Classes
Let us implement our POJO class Employee which will be used to persist the objects related to EMPLOYEE
table.
import java.util.*;
public class Employee implements java.io.Serializable {
private int id;
private int salary;
}
return id;
}
this.id = id;
}
return firstName;
}
}
return lastName;
}
}
return salary;

TUTORIALS POINT
}
}
return address;
}
}
}
We need to define another POJO class corresponding to ADDRESS entity having address related fields.
import java.util.*;
private int id;
public Address() {}
this.city = city;
this.state = state;
}
return id;
}
this.id = id;
}
return street;
}
}
return city;
}
this.city = city;
}
return state;
}
this.state = state;
}
return zipcode;
}

TUTORIALS POINT
}
}
The <component> element will be used to define the rule for all the fields associated with ADDRESS table.
<hibernate-mapping>
</meta>
</id>
<component name="address" class="Address">
</component>
</class>
</meta>
</id>
</class>

TUTORIALS POINT
 The <component> element sets the existence of different attributes of Address class inside Employee
classes.
on those records.
import java.util.*;
try{
}
Address address1 = ME.addAddress("Kondapur","Hyderabad","AP","532");
Integer empID1 = ME.addEmployee("Manoj", "Kumar", 4000, address1);
/* Let us have another address object */
Address address2 = ME.addAddress("Saharanpur","Ambehta","UP","111");
Integer empID2 = ME.addEmployee("Dilip", "Kumar", 3000, address2);
ME.listEmployees();
ME.listEmployees();
}

TUTORIALS POINT
try{
tx.commit();
}finally {
session.close();
}
return address;
}
try{
tx.commit();
}finally {
session.close();
}
return employeeID;
}
try{
}
tx.commit();
}finally {
session.close();
}
}
try{

TUTORIALS POINT
Employee employee =
tx.commit();
}finally {
session.close();
}
}
}
You would get following result on the screen, and same time records would be created in EMPLOYEE table.
Address
Street: Kondapur
City: Hyderabad
State: AP
Zipcode: 532
Address
Street: Saharanpur
City: Ambehta
State: UP
Zipcode: 111
Address
Street: Kondapur
City: Hyderabad
State: AP
Zipcode: 532
Address
Street: Saharanpur
City: Ambehta
State: UP

TUTORIALS POINT
Zipcode: 111
mysql> select id, first_name,salary, street_name, state_name from EMPLOYEE;
+----+------------+--------+-------------+------------+
| id | first_name | salary | street_name | state_name |
+----+------------+--------+-------------+------------+
| 1 | Manoj | 5000 | Kondapur | AP |
| 2 | Dilip | 3000 | Saharanpur | UP |
+----+------------+--------+-------------+------------+
mysql>

TUTORIALS POINT
Hibernate Annotations
So far you have seen how Hibernate uses XML mapping file for the transformation of data from POJO to
database tables and vice versa. Hibernate annotations is the newest way to define mappings without a use of
XML file. You can use annotations in addition to or as a replacement of XML mapping metadata.
Hibernate Annotations is the powerful way to provide the metadata for the Object and Relational Table mapping.
All the metadata is clubbed into the POJO java file along with the code this helps the user to understand the table
structure and POJO simultaneously during the development.
If you going to make your application portable to other EJB 3 compliant ORM applications, you must use
annotations to represent the mapping information but still if you want greater flexibility then you should go with
XML-based mappings.
Environment Setup for Hibernate Annotation
First of all you would have to make sure that you are using JDK 5.0 otherwise you need to upgrade your JDK to
JDK 5.0 to take advantage of the native support for annotations.
Second, you will need to install the Hibernate 3.x annotations distribution package, available from the
sourceforge: (Download Hibernate Annotation) and copy hibernate-annotations.jar, lib/hibernate-comons-
annotations.jar and lib/ejb3-persistence.jar from the Hibernate Annotations distribution to your CLASSPATH
Annotated Class Example
As I mentioned above while working with Hibernate Annotation all the metadata is clubbed into the POJO java file
along with the code this helps the user to understand the table structure and POJO simultaneously during the
development.
Consider we are going to use following EMPLOYEE table to store our objects:
PRIMARY KEY (id)
);
CHAPTER
12

TUTORIALS POINT
Following is the mapping of Employee class with annotations to map objects with the defined EMPLOYEE table:
import javax.persistence.*;
@Entity
@Table(name = "EMPLOYEE")
@Id @GeneratedValue
@Column(name = "id")
private int id;
@Column(name = "first_name")
@Column(name = "last_name")
@Column(name = "salary")
private int salary;
return id;
}
this.id = id;
}
return firstName;
}
}
return lastName;
}
}
return salary;
}
}
}
Hibernate detects that the @Id annotation is on a field and assumes that it should access properties on an object
directly through fields at runtime. If you placed the @Id annotation on the getId() method, you would enable
access to properties through getter and setter methods by default. Hence, all other annotations are also placed
on either fields or getter methods, following the selected strategy. Following section will explain the annotations
used in the above class.
@Entity Annotation
The EJB 3 standard annotations are contained in the javax.persistence package, so we import this package as
the first step. Second we used the @Entity annotation to the Employee class which marks this class as an entity
bean, so it must have a no-argument constructor that is visible with at least protected scope.

TUTORIALS POINT
@Table Annotation
The @Table annotation allows you to specify the details of the table that will be used to persist the entity in the
database.
The @Table annotation provides four attributes, allowing you to override the name of the table, its catalogue, and
its schema, and enforce unique constraints on columns in the table. For now we are using just table name which
is EMPLOYEE.
@Id and @GeneratedValue Annotations
Each entity bean will have a primary key, which you annotate on the class with the @Id annotation. The primary
key can be a single field or a combination of multiple fields depending on your table structure.
By default, the @Id annotation will automatically determine the most appropriate primary key generation strategy
to be used but you can override this by applying the @GeneratedValue annotation which takes two
parameters strategy and generator which I'm not going to discuss here, so let us use only default the default key
generation strategy. Letting Hibernate determine which generator type to use makes your code portable between
different databases.
@Column Annotation
The @Column annotation is used to specify the details of the column to which a field or property will be mapped.
You can use column annotation with the following most commonly used attributes:
 name attribute permits the name of the column to be explicitly specified.
 length attribute permits the size of the column used to map a value particularly for a String value.
 nullable attribute permits the column to be marked NOT NULL when the schema is generated.
 unique attribute permits the column to be marked as containing only unique values.
application to save few Employee's records and then we will apply CRUD operations on those records.
import org.hibernate.cfg.AnnotationConfiguration;
try{
factory = new AnnotationConfiguration().
configure().
//addPackage("com.xyz") //add package if used.
addAnnotatedClass(Employee.class).
buildSessionFactory();
}

TUTORIALS POINT
ME.listEmployees();
ME.listEmployees();
}
try{
Employee employee = new Employee();
employee.setFirstName(fname);
employee.setLastName(lname);
employee.setSalary(salary);
tx.commit();
}finally {
session.close();
}
return employeeID;
}
try{
}
tx.commit();
}finally {
session.close();
}
}
try{
Employee employee =

TUTORIALS POINT
tx.commit();
}finally {
session.close();
}
}
try{
Employee employee =
tx.commit();
}finally {
session.close();
}
}
}
Database Configuration
Now let us create hibernate.cfg.xml configuration file to define database related parameters. This time we are
not going
<session-factory>
</property>
</property>

</property>
root
</property>
cohondob
</property>
</session-factory>

TUTORIALS POINT
 Delete Employee.hbm.xml mapping file from the path.
+----+------------+-----------+--------+
+----+------------+-----------+--------+
| 29 | Zara | Ali | 5000 |
| 31 | John | Paul | 10000 |
+----+------------+-----------+--------+
mysql>

TUTORIALS POINT
Hibernate Query Language
Hibernate Query Language (HQL) is an object-oriented query language, similar to SQL, but instead of
operating on tables and columns, HQL works with persistent objects and their properties. HQL queries are
translated by Hibernate into conventional SQL queries which in turns perform action on database.
Although you can use SQL statements directly with Hibernate using Native SQL but I would recommend to use
HQL whenever possible to avoid database portability hassles, and to take advantage of Hibernate's SQL
generation and caching strategies.
Keywords like SELECT , FROM and WHERE etc. are not case sensitive but properties like table and column
names are case sensitive in HQL.
FROM Clause
You will use FROM clause if you want to load a complete persistent objects into memory. Following is the simple
syntax of using FROM clause:
String hql = "FROM Employee";
Query query = session.createQuery(hql);
List results = query.list();
If you need to fully qualify a class name in HQL, just specify the package and class name as follows:
String hql = "FROM com.hibernatebook.criteria.Employee";
AS Clause
The AS clause can be used to assign aliases to the classes in your HQL queries, specially when you have long
queries. For instance, our previous simple example would be the following:
String hql = "FROM Employee AS E";
The AS keyword is optional and you can also specify the alias directly after the class name, as follows:
CHAPTER
13

TUTORIALS POINT
String hql = "FROM Employee E";
SELECT Clause
The SELECT clause provides more control over the result set than the from clause. If you want to obtain few
properties of objects instead of the complete object, use the SELECT clause. Following is the simple syntax of
using SELECT clause to get just first_name field of the Employee object:
String hql = "SELECT E.firstName FROM Employee E";
It is notable here that Employee.firstName is a property of Employee object rather than a field of the
EMPLOYEE table.
WHERE Clause
If you want to narrow the specific objects that are returned from storage, you use the WHERE clause. Following is
the simple syntax of using WHERE clause:
String hql = "FROM Employee E WHERE E.id = 10";
ORDER BY Clause
To sort your HQL query's results, you will need to use the ORDER BY clause. You can order the results by any
property on the objects in the result set either ascending (ASC) or descending (DESC). Following is the simple
syntax of using ORDER BY clause:
String hql = "FROM Employee E WHERE E.id > 10 ORDER BY E.salary DESC";
If you wanted to sort by more than one property, you would just add the additional properties to the end of the
order by clause, separated by commas as follows:
String hql = "FROM Employee E WHERE E.id > 10 " +
"ORDER BY E.firstName DESC, E.salary DESC ";
GROUP BY Clause
This clause lets Hibernate pull information from the database and group it based on a value of an attribute and,
typically, use the result to include an aggregate value. Following is the simple syntax of using GROUP BY clause:
String hql = "SELECT SUM(E.salary), E.firtName FROM Employee E " +
"GROUP BY E.firstName";

TUTORIALS POINT
Using Named Paramters
Hibernate supports named parameters in its HQL queries. This makes writing HQL queries that accept input from
the user easy and you do not have to defend against SQL injection attacks. Following is the simple syntax of
using named parameters:
String hql = "FROM Employee E WHERE E.id = :employee_id";
query.setParameter("employee_id",10);
UPDATE Clause
Bulk updates are new to HQL with Hibernate 3, and deletes work differently in Hibernate 3 than they did in
Hibernate 2. The Query interface now contains a method called executeUpdate() for executing HQL UPDATE or
DELETE statements.
The UPDATE clause can be used to update one or more properties of an one or more objects. Following is the
simple syntax of using UPDATE clause:
String hql = "UPDATE Employee set salary = :salary " +
"WHERE id = :employee_id";
query.setParameter("salary", 1000);
query.setParameter("employee_id", 10);
int result = query.executeUpdate();
System.out.println("Rows affected: " + result);
DELETE Clause
The DELETE clause can be used to delete one or more objects. Following is the simple syntax of using DELETE
clause:
String hql = "DELETE FROM Employee " +
"WHERE id = :employee_id";
INSERT Clause
HQL supports INSERT INTO clause only where records can be inserted from one object to another object.
Following is the simple syntax of using INSERT INTO clause:
String hql = "INSERT INTO Employee(firstName, lastName, salary)" +
"SELECT firstName, lastName, salary FROM old_employee";
Aggregate Methods
HQL supports a range of aggregate methods, similar to SQL. They work the same way in HQL as in SQL and
following is the list of the available functions:

TUTORIALS POINT
S.N. Functions Description
1 avg(property name) The average of a property's value
2 count(property name or *) The number of times a property occurs in the results
3 max(property name) The maximum value of the property values
4 min(property name) The minimum value of the property values
5 sum(property name) The sum total of the property values
The distinct keyword only counts the unique values in the row set. The following query will return only unique
count:
String hql = "SELECT count(distinct E.firstName) FROM Employee E";
Pagination using Query
There are two methods of the Query interface for pagination.
S.N. Method & Description
1
Query setFirstResult(int startPosition)
This method takes an integer that represents the first row in your result set, starting with row 0.
2
Query setMaxResults(int maxResult)
This method tells Hibernate to retrieve a fixed number maxResults of objects.
Using above two methods together, we can construct a paging component in our web or Swing application.
Following is the example which you can extend to fetch 10 rows at a time:
String hql = "FROM Employee";
query.setFirstResult(1);
query.setMaxResults(10);

TUTORIALS POINT
Hibernate Criteria Queries
Hibernate provides alternate ways of manipulating objects and in turn data available in RDBMS tables.
One of the methods is Criteria API which allows you to build up a criteria query object programmatically where
you can apply filtration rules and logical conditions.
The Hibernate Session interface provides createCriteria() method which can be used to create aCriteria object
that returns instances of the persistence object's class when your application executes a criteria query.
Following is the simplest example of a criteria query is one which will simply return every object that corresponds
to the Employee class.
Criteria cr = session.createCriteria(Employee.class);
List results = cr.list();
Restrictions with Criteria
You can use add() method available for Criteria object to add restriction for a criteria query. Following is the
example to add a restriction to return the records with salary is equal to 2000:
cr.add(Restrictions.eq("salary", 2000));
Following are the few more examples covering different scenarios and can be used as per requirement:
// To get records having salary more than 2000
cr.add(Restrictions.gt("salary", 2000));
// To get records having salary less than 2000
cr.add(Restrictions.lt("salary", 2000));
// To get records having fistName starting with zara
cr.add(Restrictions.like("firstName", "zara%"));
// Case sensitive form of the above restriction.
CHAPTER
14

TUTORIALS POINT
cr.add(Restrictions.ilike("firstName", "zara%"));
// To get records having salary in between 1000 and 2000
cr.add(Restrictions.between("salary", 1000, 2000));
// To check if the given property is null
cr.add(Restrictions.isNull("salary"));
// To check if the given property is not null
cr.add(Restrictions.isNotNull("salary"));
// To check if the given property is empty
cr.add(Restrictions.isEmpty("salary"));
// To check if the given property is not empty
cr.add(Restrictions.isNotEmpty("salary"));
You can create AND or OR conditions using LogicalExpression restrictions as follows:
Criterion salary = Restrictions.gt("salary", 2000);
Criterion name = Restrictions.ilike("firstNname","zara%");
// To get records matching with OR condistions
LogicalExpression orExp = Restrictions.or(salary, name);
cr.add( orExp );
// To get records matching with AND condistions
LogicalExpression andExp = Restrictions.and(salary, name);
cr.add( andExp );
Though all the above conditions can be used directly with HQL as explained in previous tutorial.
Pagination using Criteria
There are two methods of the Criteria interface for pagination.
S.N. Method & Description
1
public Criteria setFirstResult(int firstResult)
This method takes an integer that represents the first row in your result set, starting with row 0.
2
public Criteria setMaxResults(int maxResults)
This method tells Hibernate to retrieve a fixed number maxResults of objects.
Using above two methods together, we can construct a paging component in our web or Swing application.
Following is the example which you can extend to fetch 10 rows at a time:
cr.setFirstResult(1);
cr.setMaxResults(10);

TUTORIALS POINT
Sorting the Results
The Criteria API provides the org.hibernate.criterion.Order class to sort your result set in either ascending or
descending order, according to one of your object's properties. This example demonstrates how you would use
the Order class to sort the result set:
// To get records having salary more than 2000
// To sort records in descening order
crit.addOrder(Order.desc("salary"));
// To sort records in ascending order
crit.addOrder(Order.asc("salary"));
Projections & Aggregations
The Criteria API provides the org.hibernate.criterion.Projections class which can be used to get average,
maximum or minimum of the property values. The Projections class is similar to the Restrictions class in that it
provides several static factory methods for obtaining Projection instances.
Following are the few examples covering different scenarios and can be used as per requirement:
// To get total row count.
cr.setProjection(Projections.rowCount());
// To get average of a property.
cr.setProjection(Projections.avg("salary"));
// To get distinct count of a property.
cr.setProjection(Projections.countDistinct("firstName"));
// To get maximum of a property.
cr.setProjection(Projections.max("salary"));
// To get minimum of a property.
cr.setProjection(Projections.min("salary"));
// To get sum of a property.
cr.setProjection(Projections.sum("salary"));
Criteria Queries Example
Consider the following POJO class:
private int id;

TUTORIALS POINT
private int salary;
}
return id;
}
this.id = id;
}
return firstName;
}
}
return lastName;
}
}
return salary;
}
}
}
Let us create the following EMPLOYEE table to store Employee objects:
PRIMARY KEY (id)
);
Following will be mapping file.
<hibernate-mapping>
</meta>
</id>

TUTORIALS POINT
</class>
Finally, we will create our application class with the main() method to run the application where we will
use Criteria queries:
import org.hibernate.Criteria;
import org.hibernate.criterion.Restrictions;
import org.hibernate.criterion.Projections;
try{
}
Integer empID4 = ME.addEmployee("Mohd", "Yasee", 3000);
ME.listEmployees();
/* Print Total employee's count */
ME.countEmployee();
/* Print Toatl salary */
ME.totalSalary();
}
try{
tx.commit();
}finally {
session.close();
}
return employeeID;
}

TUTORIALS POINT
/* Method to READ all the employees having salary more than 2000 */
try{
// Add restriction.
List employees = cr.list();
}
tx.commit();
}finally {
session.close();
}
}
/* Method to print total number of records */
public void countEmployee(){
try{
// To get total row count.
cr.setProjection(Projections.rowCount());
List rowCount = cr.list();
System.out.println("Total Coint: " + rowCount.get(0) );
tx.commit();
}finally {
session.close();
}
}
/* Method to print sum of salaries */
public void totalSalary(){
try{
// To get total salary.
cr.setProjection(Projections.sum("salary"));
List totalSalary = cr.list();
System.out.println("Total Salary: " + totalSalary.get(0) );
tx.commit();
}finally {
session.close();
}
}

TUTORIALS POINT
}
First Name: Mohd Last Name: Yasee Salary: 3000
Total Coint: 4
Total Salary: 15000
+----+------------+-----------+--------+
+----+------------+-----------+--------+
| 14 | Zara | Ali | 2000 |
| 15 | Daisy | Das | 5000 |
| 16 | John | Paul | 5000 |
| 17 | Mohd | Yasee | 3000 |
+----+------------+-----------+--------+
mysql>

TUTORIALS POINT
Hibernate Native SQL
You can use native SQL to express database queries if you want to utilize database-specific features
such as query hints or the CONNECT keyword in Oracle. Hibernate 3.x allows you to specify handwritten SQL,
including stored procedures, for all create, update, delete, and load operations.
Your application will create a native SQL query from the session with the createSQLQuery() method on the
Session interface:
public SQLQuery createSQLQuery(String sqlString) throws HibernateException
After you pass a string containing the SQL query to the createSQLQuery() method, you can associate the SQL
result with either an existing Hibernate entity, a join, or a scalar result using addEntity(), addJoin(), and
addScalar() methods respectively.
Scalar queries
The most basic SQL query is to get a list of scalars (values) from one or more tables. Following is the syntax for
using native SQL for scalar values:
String sql = "SELECT first_name, salary FROM EMPLOYEE";
SQLQuery query = session.createSQLQuery(sql);
query.setResultTransformer(Criteria.ALIAS_TO_ENTITY_MAP);
Entity queries
The above queries were all about returning scalar values, basically returning the "raw" values from the resultset.
The following is the syntax to get entity objects as a whole from a native sql query via addEntity().
String sql = "SELECT * FROM EMPLOYEE";
query.addEntity(Employee.class);
CHAPTER
15

TUTORIALS POINT
Named SQL queries
The following is the syntax to get entity objects from a native sql query via addEntity() and using named SQL
query.
String sql = "SELECT * FROM EMPLOYEE WHERE id = :employee_id";
Native SQL Example
Consider the following POJO class:
private int id;
private int salary;
}
return id;
}
this.id = id;
}
return firstName;
}
}
return lastName;
}
}
return salary;
}
}
}

TUTORIALS POINT
PRIMARY KEY (id)
);
Following will be mapping file.
<hibernate-mapping>
</meta>
</id>
</class>
Finally, we will create our application class with the main() method to run the application where we will use Native
SQL queries:
import java.util.*;
import org.hibernate.SQLQuery;
import org.hibernate.Criteria;
import org.hibernate.Hibernate;
try{
}
Integer empID4 = ME.addEmployee("Mohd", "Yasee", 3000);
/* List down employees and their salary using Scalar Query */
ME.listEmployeesScalar();
/* List down complete employees information using Entity Query */

TUTORIALS POINT
ME.listEmployeesEntity();
}
try{
tx.commit();
}finally {
session.close();
}
return employeeID;
}
/* Method to READ all the employees using Scalar Query */
public void listEmployeesScalar( ){
try{
String sql = "SELECT first_name, salary FROM EMPLOYEE";
query.setResultTransformer(Criteria.ALIAS_TO_ENTITY_MAP);
List data = query.list();
for(Object object : data)
{
Map row = (Map)object;
System.out.print("First Name: " + row.get("first_name"));
System.out.println(", Salary: " + row.get("salary"));
}
tx.commit();
}finally {
session.close();
}
}
/* Method to READ all the employees using Entity Query */
public void listEmployeesEntity( ){
try{
String sql = "SELECT * FROM EMPLOYEE";
List employees = query.list();
}
tx.commit();

TUTORIALS POINT
}finally {
session.close();
}
}
}
First Name: Zara, Salary: 2000
First Name: Daisy, Salary: 5000
First Name: John, Salary: 5000
First Name: Mohd, Salary: 3000
First Name: Mohd Last Name: Yasee Salary: 3000
+----+------------+-----------+--------+
+----+------------+-----------+--------+
| 26 | Zara | Ali | 2000 |
| 27 | Daisy | Das | 5000 |
| 28 | John | Paul | 5000 |
| 29 | Mohd | Yasee | 3000 |
+----+------------+-----------+--------+
mysql>

TUTORIALS POINT
Hibernate Caching
Caching is all about application performance optimization and it sits between your application and the
database to avoid the number of database hits as many as possible to give a better performance for performance
critical applications.
Caching is important to Hibernate as well which utilizes a multilevel caching schemes as explained below:
First-level cache
The first-level cache is the Session cache and is a mandatory cache through which all requests must pass. The
Session object keeps an object under its own power before committing it to the database.
CHAPTER
16

TUTORIALS POINT
If you issue multiple updates to an object, Hibernate tries to delay doing the update as long as possible to reduce
the number of update SQL statements issued. If you close the session, all the objects being cached are lost and
either persisted or updated in the database.
Second-level cache
Second level cache is an optional cache and first-level cache will always be consulted before any attempt is made
to locate an object in the second-level cache. The second-level cache can be configured on a per-class and per-
collection basis and mainly responsible for caching objects across sessions.
Any third-party cache can be used with Hibernate. An org.hibernate.cache.CacheProvider interface is provided,
which must be implemented to provide Hibernate with a handle to the cache implementation.
Query-level cache
Hibernate also implements a cache for query resultsets that integrates closely with the second-level cache.
This is an optional feature and requires two additional physical cache regions that hold the cached query results
and the timestamps when a table was last updated. This is only useful for queries that are run frequently with the
same parameters.
The Second Level Cache
Hibernate uses first-level cache by default and you have nothing to do to use first-level cache. Let's go straight to
the optional second-level cache. Not all classes benefit from caching, so it's important to be able to disable the
second-level cache
The Hibernate second-level cache is set up in two steps. First, you have to decide which concurrency strategy to
use. After that, you configure cache expiration and physical cache attributes using the cache provider.
Concurrency strategies
A concurrency strategy is a mediator which responsible for storing items of data in the cache and retrieving them
from the cache. If you are going to enable a second-level cache, you will have to decide, for each persistent class
and collection, which cache concurrency strategy to use.
 Transactional: Use this strategy for read-mostly data where it is critical to prevent stale data in concurrent
transactions,in the rare case of an update.
 Read-write: Again use this strategy for read-mostly data where it is critical to prevent stale data in concurrent
transactions,in the rare case of an update.
 Nonstrict-read-write: This strategy makes no guarantee of consistency between the cache and the database.
Use this strategy if data hardly ever changes and a small likelihood of stale data is not of critical concern.
 Read-only: A concurrency strategy suitable for data which never changes. Use it for reference data only.
If we are going to use second-level caching for our Employee class, let us add the mapping element required to
tell Hibernate to cache Employee instances using read-write strategy.
<hibernate-mapping>

TUTORIALS POINT
</meta>
<cache usage="read-write"/>
</id>
</class>
The usage="read-write" attribute tells Hibernate to use a read-write concurrency strategy for the defined cache.
Cache provider
Your next step after considering the concurrency strategies you will use for your cache candidate classes is to
pick a cache provider. Hibernate forces you to choose a single cache provider for the whole application.
S.N. Cache Name Description
1 EHCache
It can cache in memory or on disk and clustered caching and it
supports the optional Hibernate query result cache.
2 OSCache
Supports caching to memory and disk in a single JVM, with a rich set
of expiration policies and query cache support.
3 warmCache
A cluster cache based on JGroups. It uses clustered invalidation but
doesn't support the Hibernate query cache
4 JBoss Cache
A fully transactional replicated clustered cache also based on the
JGroups multicast library. It supports replication or invalidation,
synchronous or asynchronous communication, and optimistic and
pessimistic locking. The Hibernate query cache is supported
Every cache provider is not compatible with every concurrency strategy. The following compatibility matrix will
help you choose an appropriate combination.
Strategy/Provider Read-only Nonstrictread-write Read-write
Transaction
al
EHCache X X X
OSCache X X X
SwarmCache X X
JBoss Cache X X
You will specify a cache provider in hibernate.cfg.xml configuration file. We choose EHCache as our second-level
cache provider:

TUTORIALS POINT
<session-factory>
</property>
</property>
</property>
root
</property>
root123
</property>
<property name="hibernate.cache.provider_class">
org.hibernate.cache.EhCacheProvider
</property>
</session-factory>
Now, you need to specify the properties of the cache regions. EHCache has its own configuration
file,ehcache.xml, which should be in the CLASSPATH of the application. A cache configuration in ehcache.xml
for the Employee class may look like this:
<diskStore path="java.io.tmpdir"/>
<defaultCache
maxElementsInMemory="1000"
eternal="false"
timeToIdleSeconds="120"
timeToLiveSeconds="120"
overflowToDisk="true"
/>
<cache name="Employee"
maxElementsInMemory="500"
eternal="true"
timeToIdleSeconds="0"
timeToLiveSeconds="0"
overflowToDisk="false"
/>
That's it, now we have second-level caching enabled for the Employee class and Hibernate now hits the second-
level cache whenever you navigate to a Employee or when you load a Employee by identifier.
You should analyze your all the classes and choose appropriate caching strategy for each of the classes.
Sometime, second-level caching may downgrade the performance of the application. So it is recommended to
benchmark your application first without enabling caching and later on enable your well suited caching and check
the performance. If caching is not improving system performance then there is no point in enabling any type of
caching.

TUTORIALS POINT
The Query-level Cache
To use the query cache, you must first activate it using the hibernate.cache.use_query_cache="true"property
in the configuration file. By setting this property to true, you make Hibernate create the necessary caches in
memory to hold the query and identifier sets.
Next, to use the query cache, you use the setCacheable(Boolean) method of the Query class. For example:
Session session = SessionFactory.openSession();
Query query = session.createQuery("FROM EMPLOYEE");
query.setCacheable(true);
List users = query.list();
SessionFactory.closeSession();
Hibernate also supports very fine-grained cache support through the concept of a cache region. A cache region is
part of the cache that's given a name.
Query query = session.createQuery("FROM EMPLOYEE");
query.setCacheable(true);
query.setCacheRegion("employee");
List users = query.list();
SessionFactory.closeSession();
This code uses the method to tell Hibernate to store and look for the query in the employee area of the cache.

TUTORIALS POINT
Hibernate Batch Processing
Consider a situation when you need to upload a large number of records into your database using
Hibernate. Following is the code snippet to achieve this using Hibernate:
Transaction tx = session.beginTransaction();
for ( int i=0; i<100000; i++ ) {
Employee employee = new Employee(.....);
session.save(employee);
}
tx.commit();
session.close();
Because by default, Hibernate will cache all the persisted objects in the session-level cache and ultimately your
application would fall over with an OutOfMemoryException somewhere around the 50,000th row. You can
resolve this problem if you are using batch processing with Hibernate.
To use the batch processing feature, first set hibernate.jdbc.batch_size as batch size to a number either at 20
or 50 depending on object size. This will tell the hibernate container that every X rows to be inserted as batch. To
implement this in your code we would need to do little modification as follows:
for ( int i=0; i<100000; i++ ) {
Employee employee = new Employee(.....);
if( i % 50 == 0 ) { // Same as the JDBC batch size
//flush a batch of inserts and release memory:
session.flush();
session.clear();
}
}
tx.commit();
session.close();
Above code will work fine for the INSERT operation, but if you are willing to make UPDATE operation then you
can achieve using the following code:
Session session = sessionFactory.openSession();
CHAPTER
17

TUTORIALS POINT
ScrollableResults employeeCursor = session.createQuery("FROM EMPLOYEE")
.scroll();
int count = 0;
while ( employeeCursor.next() ) {
Employee employee = (Employee) employeeCursor.get(0);
employee.updateEmployee();
seession.update(employee);
if ( ++count % 50 == 0 ) {
session.flush();
session.clear();
}
}
tx.commit();
session.close();
Batch Processing Example
Let us modify configuration file as to add hibernate.jdbc.batch_size property:
<session-factory>
</property>
</property>
</property>
root
</property>
root123
</property>
<property name="hibernate.jdbc.batch_size">
50
</property>
</session-factory>
Consider the following POJO Employee class:

TUTORIALS POINT
private int id;
private int salary;
}
return id;
}
this.id = id;
}
return firstName;
}
}
return lastName;
}
}
return salary;
}
}
}
PRIMARY KEY (id)
);
Following will be mapping file to map Employee objects with EMPLOYEE table.
<hibernate-mapping>
</meta>

TUTORIALS POINT
</id>
</class>
Finally, we will create our application class with the main() method to run the application where we will
use flush() and clear() methods available with Session object so that Hibernate keep writing these records into
the database instead of caching them in the memory.
import java.util.*;
try{
}
/* Add employee records in batches */
ME.addEmployees( );
}
/* Method to create employee records in batches */
public void addEmployees( ){
try{
for ( int i=0; i<100000; i++ ) {
String fname = "First Name " + i;
String lname = "Last Name " + i;
Integer salary = i;
if( i % 50 == 0 ) {
session.flush();
session.clear();
}
}
tx.commit();
}finally {
session.close();
}
return ;
}
}

TUTORIALS POINT
 Create hibernate.cfg.xml configuration file as explained above.
 Execute ManageEmployee binary to run the program which will create 100000 records in EMPLOYEE table.

TUTORIALS POINT
Hibernate Interceptors
As you have learnt that in Hibernate, an object will be created and persisted. Once the object has been
changed, it must be saved back to the database. This process continues until the next time the object is needed,
and it will be loaded from the persistent store.
Thus an object passes through different stages in its life cycle and Interceptor Interface provides methods which
can be called at different stages to perform some required tasks. These methods are callbacks from the session
to the application, allowing the application to inspect and/or manipulate properties of a persistent object before it
is saved, updated, deleted or loaded. Following is the list of all the methods available within the Interceptor
interface:
S.N. Method and Description
1
findDirty()
This method is be called when the flush() method is called on a Session object.
2
instantiate()
This method is called when a persisted class is instantiated.
3
isUnsaved()
This method is called when an object is passed to the saveOrUpdate() method/
4
onDelete()
This method is called before an object is deleted.
5
onFlushDirty()
This method is called when Hibernate detects that an object is dirty (ie. have been
changed) during a flush i.e. update operation.
6
onLoad()
This method is called before an object is initialized.
7
onSave()
This method is called before an object is saved.
8
postFlush()
This method is called after a flush has occurred and an object has been updated in
memory.
9
preFlush()
This method is called before a flush.
Hibernate Interceptor gives us total control over how an object will look to both the application and the database.
CHAPTER
18

TUTORIALS POINT
How to use Interceptors?
To build an interceptor you can either implement Interceptor class directly or extend EmptyInterceptorclass.
Following will be the simple steps to use Hibernate Interceptor functionality.
Create Interceptors
We will extend EmptyInterceptor in our example where Interceptor's method will be called automatically
when Employee object is created and updated. You can implement more methods as per your requirements.
import java.io.Serializable;
import org.hibernate.EmptyInterceptor;
import org.hibernate.type.Type;
public class MyInterceptor extends EmptyInterceptor {
private int updates;
private int creates;
private int loads;
public void onDelete(Object entity,
Serializable id,
Object[] state,
String[] propertyNames,
Type[] types) {
// do nothing
}
// This method is called when Employee object gets updated.
public boolean onFlushDirty(Object entity,
Serializable id,
Object[] currentState,
Object[] previousState,
Type[] types) {
if ( entity instanceof Employee ) {
System.out.println("Update Operation");
return true;
}
return false;
}
public boolean onLoad(Object entity,
Serializable id,
Object[] state,
Type[] types) {
// do nothing
return true;
}
// This method is called when Employee object gets created.
public boolean onSave(Object entity,
Serializable id,
Object[] state,
Type[] types) {
if ( entity instanceof Employee ) {
System.out.println("Create Operation");
return true;
}
return false;
}
//called before commit into database
public void preFlush(Iterator iterator) {
System.out.println("preFlush");

TUTORIALS POINT
}
//called after committed into database
public void postFlush(Iterator iterator) {
System.out.println("postFlush");
}
}
Create POJO Classes
Now let us modify a little bit our first example where we used EMPLOYEE table and Employee class to play with:
private int id;
private int salary;
}
return id;
}
this.id = id;
}
return firstName;
}
}
return lastName;
}
}
return salary;
}
}
}
Create Database Tables
Second step would be creating tables in your database. There would be one table corresponding to each object
you are willing to provide persistence. Consider above objects need to be stored and retrieved into the following
RDBMS table:

TUTORIALS POINT
PRIMARY KEY (id)
);
Create Mapping Configuration File
This step is to create a mapping file that instructs Hibernate how to map the defined class or classes to the
database tables.
<hibernate-mapping>
</meta>
</id>
</class>
Finally, we will create our application class with the main() method to run the application. Here it should be noted
that while creating session object we used our Interceptor class as an argument.
try{
}

TUTORIALS POINT
ME.listEmployees();
ME.listEmployees();
}
Session session = factory.openSession( new MyInterceptor() );
try{
tx.commit();
}finally {
session.close();
}
return employeeID;
}
try{
}
tx.commit();
}finally {
session.close();
}
}
try{
Employee employee =

TUTORIALS POINT
tx.commit();
}finally {
session.close();
}
}
try{
Employee employee =
tx.commit();
}finally {
session.close();
}
}
}
 Create MyInterceptor.java source file as shown above and compile it.
Create Operation
preFlush
postFlush
Create Operation
preFlush
postFlush
Create Operation
preFlush
postFlush

TUTORIALS POINT
preFlush
postFlush
preFlush
Update Operation
postFlush
preFlush
postFlush
preFlush
postFlush
+----+------------+-----------+--------+
+----+------------+-----------+--------+
| 29 | Zara | Ali | 5000 |
| 31 | John | Paul | 10000 |
+----+------------+-----------+--------+
mysql>

Hibernate tutorial

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