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JDBC Tutorial

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The JDBC API is a Java API that can access any kind of tabular data, especially data
stored in a Relational Database. JDBC stands for Java Database Connectivity.

JDBC works with Java on a variety of platforms, such as Windows, Mac OS, and the
various versions of UNIX. This tutorial gives an initial push to start you with log4J. For
more detail kindly check tutorialspoint.com/jdbc

What is JDBC?
JDBC stands for Java Database Connectivity, which is a standard Java API for database-
independent connectivity between the Java programming language and a wide range of
databases.

The JDBC library includes APIs for each of the tasks commonly associated with database usage:

 Making a connection to a database
 Creating SQL or MySQL statements
 Executing that SQL or MySQL queries in the database
 Viewing & Modifying the resulting records

Pre-Requisite:
You need to have good understanding on the following two subjects to learn JDBC:

1. Core JAVA Programming
2. SQL or MySQL Database

JDBC - Environment Setup:
Make sure you have done following setup:

1. Core JAVA Installation
2. SQL or MySQL Database Installation

Apart from the above you need to setup a database which you would use for your project.
Assuming this is EMP and you have created on table Employees within the same database.

Creating JDBC Application:
There are six steps involved in building a JDBC application which I'm going to brief in this
tutorial:

Import the packages:

This requires that you include the packages containing the JDBC classes needed for database
programming. Most often, using import java.sql.* will suffice as follows:

//STEP 1. Import required packages
import java.sql.*;

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Register the JDBC driver:

This requires that you initialize a driver so you can open a communications channel with the
database. Following is the code snippet to achieve this:

//STEP 2: Register JDBC driver
Class.forName("com.mysql.jdbc.Driver");

Open a connection:

This requires using the DriverManager.getConnection() method to create a Connection object,
which represents a physical connection with the database as follows:

//STEP 3: Open a connection
// Database credentials
static final String USER = "username";
static final String PASS = "password";
System.out.println("Connecting to database...");
conn = DriverManager.getConnection(DB_URL,USER,PASS);

Execute a query:

This requires using an object of type Statement or PreparedStatement for building and
submitting an SQL statement to the database as follows:

//STEP 4: Execute a query
System.out.println("Creating statement...");
stmt = conn.createStatement();
String sql;
sql = "SELECT id, first, last, age FROM Employees";
ResultSet rs = stmt.executeQuery(sql);

If there is an SQL UPDATE,INSERT or DELETE statement required, then following code snippet
would be required:

String sql;
sql = "DELETE FROM Employees";
ResultSet rs = stmt.executeUpdate(sql);

Extract data from result set:

This step is required in case you are fetching data from the database. You can use the
appropriate ResultSet.getXXX() method to retrieve the data from the result set as follows:

//STEP 5: Extract data from result set
while(rs.next()){
//Retrieve by column name
int id = rs.getInt("id");
int age = rs.getInt("age");
String first = rs.getString("first");
String last = rs.getString("last");

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//Display values
System.out.print("ID: " + id);
System.out.print(", Age: " + age);
System.out.print(", First: " + first);
System.out.println(", Last: " + last);
}

Clean up the environment:

You should explicitly close all database resources versus relying on the JVM's garbage collection
as follows:

//STEP 6: Clean-up environment
rs.close();
stmt.close();
conn.close();

JDBC Program:
Based on the above steps, we can have following consolidated sample code which we can use as
a template while writing our JDBC code:

This sample code has been written based on the environment and database setup done in
Environment chapter.

import java.sql.*;

public class FirstExample {
// JDBC driver name and database URL
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
static final String DB_URL = "jdbc:mysql://localhost/EMP";


public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
try{

conn = DriverManager.getConnection(DB_URL,USER,PASS);

String sql;
sql = "SELECT id, first, last, age FROM Employees";

while(rs.next()){

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//Display values
}
//STEP 6: Clean-up environment
rs.close();
stmt.close();
conn.close();
}catch(SQLException se){
//Handle errors for JDBC
se.printStackTrace();
}catch(Exception e){
//Handle errors for Class.forName
e.printStackTrace();
}finally{
//finally block used to close resources
try{
if(stmt!=null)
stmt.close();
}catch(SQLException se2){
}// nothing we can do
try{
if(conn!=null)
conn.close();
}//end finally try
}//end try
System.out.println("Goodbye!");
}//end main
}//end FirstExample

Now let us compile above example as follows:

C:>javac FirstExample.java
C:>

When you run FirstExample, it produces following result:

C:>java FirstExample
Connecting to database...
Creating statement...
ID: 100, Age: 18, First: Zara, Last: Ali
ID: 101, Age: 25, First: Mahnaz, Last: Fatma
ID: 102, Age: 30, First: Zaid, Last: Khan
ID: 103, Age: 28, First: Sumit, Last: Mittal
C:>

SQLException Methods:

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A SQLException can occur both in the driver and the database. When such an exception occurs,
an object of type SQLException will be passed to the catch clause.

The passed SQLException object has the following methods available for retrieving additional
information about the exception:

Method Description

getErrorCode( ) Gets the error number associated with the exception.

getMessage( ) Gets the JDBC driver's error message for an error
handled by the driver or gets the Oracle error number
and message for a database error.

getSQLState( ) Gets the XOPEN SQLstate string. For a JDBC driver
error, no useful information is returned from this
method. For a database error, the five-digit XOPEN
SQLstate code is returned. This method can return
null.

getNextException( ) Gets the next Exception object in the exception chain.

printStackTrace( ) Prints the current exception, or throwable, and its
backtrace to a standard error stream.

printStackTrace(PrintStream s) Prints this throwable and its backtrace to the print
stream you specify.

printStackTrace(PrintWriter w) Prints this throwable and its backtrace to the print
writer you specify.

By utilizing the information available from the Exception object, you can catch an exception and
continue your program appropriately. Here is the general form of a try block:

try {
// Your risky code goes between these curly braces!!!
}
catch(Exception ex) {
// Your exception handling code goes between these
// curly braces, similar to the exception clause
// in a PL/SQL block.
}
finally {
// Your must-always-be-executed code goes between these
// curly braces. Like closing database connection.
}

JDBC - Data Types:

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The following table summarizes the default JDBC data type that the Java data type is converted
to when you call the setXXX() method of the PreparedStatement or CallableStatement object or
the ResultSet.updateXXX() method.

SQL JDBC/Java setXXX updateXXX

VARCHAR java.lang.String setString updateString

CHAR java.lang.String setString updateString

LONGVARCHAR java.lang.String setString updateString

BIT boolean setBoolean updateBoolean

NUMERIC java.math.BigDecimal setBigDecimal updateBigDecimal

TINYINT byte setByte updateByte

SMALLINT short setShort updateShort

INTEGER int setInt updateInt

BIGINT long setLong updateLong

REAL float setFloat updateFloat

FLOAT float setFloat updateFloat

DOUBLE double setDouble updateDouble

VARBINARY byte[ ] setBytes updateBytes

BINARY byte[ ] setBytes updateBytes

DATE java.sql.Date setDate updateDate

TIME java.sql.Time setTime updateTime

TIMESTAMP java.sql.Timestamp setTimestamp updateTimestamp

CLOB java.sql.Clob setClob updateClob

BLOB java.sql.Blob setBlob updateBlob

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ARRAY java.sql.Array setARRAY updateARRAY

REF java.sql.Ref SetRef updateRef

STRUCT java.sql.Struct SetStruct updateStruct

JDBC 3.0 has enhanced support for BLOB, CLOB, ARRAY, and REF data types. The ResultSet
object now has updateBLOB(), updateCLOB(), updateArray(), and updateRef() methods that
enable you to directly manipulate the respective data on the server.

The setXXX() and updateXXX() methods enable you to convert specific Java types to specific
JDBC data types. The methods, setObject() and updateObject(), enable you to map almost any
Java type to a JDBC data type.

ResultSet object provides corresponding getXXX() method for each data type to retrieve column
value. Each method can be used with column name or by its ordinal position.

SQL JDBC/Java setXXX getXXX

VARCHAR java.lang.String setString getString

CHAR java.lang.String setString getString

LONGVARCHAR java.lang.String setString getString

BIT boolean setBoolean getBoolean

NUMERIC java.math.BigDecimal setBigDecimal getBigDecimal

TINYINT byte setByte getByte

SMALLINT short setShort getShort

INTEGER int setInt getInt

BIGINT long setLong getLong

REAL float setFloat getFloat

FLOAT float setFloat getFloat

DOUBLE double setDouble getDouble

VARBINARY byte[ ] setBytes getBytes

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BINARY byte[ ] setBytes getBytes

DATE java.sql.Date setDate getDate

TIME java.sql.Time setTime getTime

TIMESTAMP java.sql.Timestamp setTimestamp getTimestamp

CLOB java.sql.Clob setClob getClob

BLOB java.sql.Blob setBlob getBlob

ARRAY java.sql.Array setARRAY getARRAY

REF java.sql.Ref SetRef getRef

STRUCT java.sql.Struct SetStruct getStruct

JDBC - Create Database Example
This tutorial provides an example on how to create a Database using JDBC application. Before
executing following example, make sure you have the following in place:

 You should have admin privilege to create a database in the given schema. To execute
the following example you need to replace username and password with your actual
user name and password.
 Your MySQL or whatever database you are using is up and running.

Required Steps:
There are following steps required to create a new Database using JDBC application:

1. Import the packages . Requires that you include the packages containing the JDBC
classes needed for database programming. Most often, using import java.sql.* will
suffice.
2. Register the JDBC driver . Requires that you initialize a driver so you can open a
communications channel with the database.
3. Open a connection . Requires using the DriverManager.getConnection() method to
create a Connection object, which represents a physical connection with datbase server.

To create a new database, you need not to give any database name while preparing
database URL as mentioned in the below example.

4. Execute a query . Requires using an object of type Statement for building and
submitting an SQL statement to the database.
5. Clean up the environment . Requires explicitly closing all database resources versus
relying on the JVM's garbage collection.

Sample Code:

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Copy and past following example in JDBCExample.java, compile and run as follows:

import java.sql.*;

public class JDBCExample {
static final String DB_URL = "jdbc:mysql://localhost/";


try{

conn = DriverManager.getConnection(DB_URL, USER, PASS);

System.out.println("Creating database...");

String sql = "CREATE DATABASE STUDENTS";
stmt.executeUpdate(sql);
System.out.println("Database created successfully...");
}finally{
try{
if(stmt!=null)
stmt.close();
}catch(SQLException se2){
}// nothing we can do
try{
if(conn!=null)
conn.close();
}//end finally try
}//end try
}//end main
}//end JDBCExample


C:>javac JDBCExample.java
C:>

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When you run JDBCExample, it produces following result:

C:>java JDBCExample
Connecting to database...
Creating database...
Database created successfully...
Goodbye!
C:>

JDBC - Select Database Example
This tutorial provides an example on how to select a Database using JDBC application. Before

 To execute the following example you need to replace username and password with
your actual user name and password.

Required Steps:

1. Import the packages . Requires that you include the packages containing the JDBC
suffice.
2. Register the JDBC driver . Requires that you initialize a driver so you can open a
3. Open a connection . Requires using the DriverManager.getConnection() method to
create a Connection object, which represents a physical connection with a selected
database.

Selection of database is made while you prepare database URL. Following example
would make connection with STUDENTS database.


Sample Code:

import java.sql.*;

static final String DB_URL = "jdbc:mysql://localhost/STUDENTS";


try{

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System.out.println("Connecting to a selected database...");
System.out.println("Connected database successfully...");
}finally{
try{
if(conn!=null)
conn.close();
}//end finally try
}//end try
}//end main
}//end JDBCExample


C:>


C:>java JDBCExample
Connecting to a selected database...
Connected database successfully...
Goodbye!
C:>

JDBC - Drop Database Example
This tutorial provides an example on how to drop an existing Database using JDBC application.
Before executing following example, make sure you have the following in place:

 To execute the following example you need to replace username and password with
your actual user name and password.

NOTE: This is a serious operation and you have to make a firm decision before proceeding to
delete a database because everything you have in your database would be lost.

Required Steps:

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1. Import the packages: Requires that you include the packages containing the JDBC
suffice.
2. Register the JDBC driver: Requires that you initialize a driver so you can open a
3. Open a connection: Requires using the DriverManager.getConnection() method to
create a Connection object, which represents a physical connection with a database
server.

Deleting a database does not require database name to be in your database URL.
Following example would delete STUDENTS database.

4. Execute a query: Requires using an object of type Statement for building and
submitting an SQL statement to delete the database.

Sample Code:

import java.sql.*;

static final String DB_URL = "jdbc:mysql://localhost/";


try{


System.out.println("Deleting database...");

String sql = "DROP DATABASE STUDENTS";
System.out.println("Database deleted successfully...");
}finally{

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try{
if(stmt!=null)
conn.close();
}// do nothing
try{
if(conn!=null)
conn.close();
}//end finally try
}//end try
}//end main
}//end JDBCExample


C:>


C:>java JDBCExample
Deleting database...
Database deleted successfully...
Goodbye!
C:>

JDBC - Create Tables Example
This tutorial provides an example on how to create a table using JDBC application. Before

 To execute the following example you can replace username and password with your
actual user name and password.

Required Steps:

suffice.
server.
submitting an SQL statement to create a table in a seleted database.

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Sample Code:

import java.sql.*;



try{


System.out.println("Creating table in given database...");

String sql = "CREATE TABLE REGISTRATION " +
"(id INTEGER not NULL, " +
" first VARCHAR(255), " +
" last VARCHAR(255), " +
" age INTEGER, " +
" PRIMARY KEY ( id ))";

System.out.println("Created table in given database...");
}finally{
try{
if(stmt!=null)
conn.close();
}// do nothing
try{
if(conn!=null)
conn.close();
}//end finally try

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}//end try
}//end main
}//end JDBCExample


C:>


C:>java JDBCExample
Creating table in given database...
Created table in given database...
Goodbye!
C:>

JDBC - Drop Tables Example
This tutorial provides an example on how to delete a table using JDBC application. Before


NOTE: This is a serious operation and you have to make a firm decision before proceeding to
delete a table because everything you have in your table would be lost.

Required Steps:

suffice.
server.
submitting an SQL statement to drop a table in a seleted database.

Sample Code:


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import java.sql.*;



try{


System.out.println("Deleting table in given database...");

String sql = "DROP TABLE REGISTRATION ";

System.out.println("Table deleted in given database...");
}finally{
try{
if(stmt!=null)
conn.close();
}// do nothing
try{
if(conn!=null)
conn.close();
}//end finally try
}//end try
}//end main
}//end JDBCExample


C:>

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C:>java JDBCExample
Deleting table in given database...
Table deleted in given database...
Goodbye!
C:>

JDBC - Insert Records Example
This tutorial provides an example on how to insert records in a table using JDBC application.


Required Steps:

suffice.
server.
submitting an SQL statement to insert records into a table.
5. Clean up the environment: Requires explicitly closing all database resources versus

Sample Code:

import java.sql.*;



try{

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System.out.println("Inserting records into the table...");

String sql = "INSERT INTO Registration " +
"VALUES (100, 'Zara', 'Ali', 18)";
sql = "INSERT INTO Registration " +
"VALUES (101, 'Mahnaz', 'Fatma', 25)";
"VALUES (102, 'Zaid', 'Khan', 30)";
"VALUES(103, 'Sumit', 'Mittal', 28)";
System.out.println("Inserted records into the table...");

}finally{
try{
if(stmt!=null)
conn.close();
}// do nothing
try{
if(conn!=null)
conn.close();
}//end finally try
}//end try
}//end main
}//end JDBCExample


C:>


C:>java JDBCExample

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Inserting records into the table...
Inserted records into the table...
Goodbye!
C:>

JDBC - Select Records Example
This tutorial provides an example on how to select/ fetch records from a table using JDBC
application. Before executing following example, make sure you have the following in place:


Required Steps:

suffice.
server.
submitting an SQL statement to select (i.e. fetch ) records from a table.
5. Extract Data: Once SQL query is executed, you can fetch records from the table.

Sample Code:

import java.sql.*;



try{


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String sql = "SELECT id, first, last, age FROM Registration";
while(rs.next()){

//Display values
}
rs.close();
}finally{
try{
if(stmt!=null)
conn.close();
}// do nothing
try{
if(conn!=null)
conn.close();
}//end finally try
}//end try
}//end main
}//end JDBCExample


C:>


C:>java JDBCExample

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Goodbye!
C:>

JDBC - Update Records Example
This tutorial provides an example on how to update records in a table using JDBC application.


Required Steps:

suffice.
server.
submitting an SQL statement to update records in a table. This Query makes use of IN
and WHERE clause to update conditional records.

Sample Code:

import java.sql.*;



try{

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String sql = "UPDATE Registration " +
"SET age = 30 WHERE id in (100, 101)";

// Now you can extract all the records
// to see the updated records
sql = "SELECT id, first, last, age FROM Registration";

while(rs.next()){

//Display values
}
rs.close();
}finally{
try{
if(stmt!=null)
conn.close();
}// do nothing
try{
if(conn!=null)
conn.close();
}//end finally try
}//end try
}//end main
}//end JDBCExample


C:>

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C:>java JDBCExample
Goodbye!
C:>

JDBC - Delete Records Example
This tutorial provides an example on how to delete records from a table using JDBC application.


Required Steps:

suffice.
server.
submitting an SQL statement to delete records from a table. This Query makes use of
WHERE clause to delete conditional records.

Sample Code:

import java.sql.*;




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try{


String sql = "DELETE FROM Registration " +
"WHERE id = 101";

// Now you can extract all the records
// to see the remaining records
sql = "SELECT id, first, last, age FROM Registration";

while(rs.next()){

//Display values
}
rs.close();
}finally{
try{
if(stmt!=null)
conn.close();
}// do nothing
try{
if(conn!=null)
conn.close();
}//end finally try
}//end try
}//end main
}//end JDBCExample

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C:>


C:>java JDBCExample
Goodbye!
C:>

JDBC - Batch Processing:
Batch Processing allows you to group related SQL statements into a batch and submit them with
one call to the database.

When you send several SQL statements to the database at once, you reduce the amount of
communication overhead, thereby improving performance.

 JDBC drivers are not required to support this feature. You should use the
DatabaseMetaData.supportsBatchUpdates() method to determine if the target database
supports batch update processing. The method returns true if your JDBC driver
supports this feature.
 The addBatch() method of Statement, PreparedStatement, and CallableStatement is
used to add individual statements to the batch. The executeBatch() is used to start
the execution of all the statements grouped together.
 The executeBatch() returns an array of integers, and each element of the array
represents the update count for the respective update statement.
 Just as you can add statements to a batch for processing, you can remove them with
the clearBatch() method. This method removes all the statements you added with the
addBatch() method. However, you cannot selectively choose which statement to
remove.

JDBC - Streaming Data:
A PreparedStatement object has the ability to use input and output streams to supply parameter
data. This enables you to place entire files into database columns that can hold large values,
such as CLOB and BLOB data types.

There are following methods which can be used to stream data:

1. setAsciiStream(): This method is used to supply large ASCII values.
2. setCharacterStream(): This method is used to supply large UNICODE values.
3. setBinaryStream(): This method is used to supply large binary values.

The setXXXStream() method requires an extra parameter, the file size, besides the parameter
placeholder. This parameter informs the driver how much data should be sent to the database
using the stream.

Further Detail:

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Refer to the link http://www.tutorialspoint.com/jdbc

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