Spring jdbc dao
- 1. Spring JDBC/DAO By → Anuj Kumar Singh
- 2. What is Spring DAO (Data Access Object) DAO is used to read and write data to and from database respectively.The table below shows the responsibility of Spring and User. Note : The Spring Framework takes care of all the low-level details that can make JDBC such a tedious API to develop with
- 3. Action Spring User Define Connection Parameter Yes Open the Connection Yes Specify the SQL statement Yes Declare parameters and provide parameter values Yes Prepare and Execute the Statement Yes Set up the loop to iterate through the result (if any) Yes Do the work for each iteration Yes Process any Exception Yes Handle Transactions Yes Close the Connection,Statement and ResultSet Yes
- 4. Steps for DAO We have to follow three steps while configuring the Spring Context in XML. Step 1: Configure Data Source 1. Driver Based Data Source 2. JNDI Data Source 3. Pooled Data Source Step 2: Configure JDBC Template 1. JDBC Template 2. NamedParameter JDBC Template 3. Simple JDBC Template
- 5. Step 3: Configure custom DAO Class Step 1: Configure Data Source The very first step you need to work on database is configuring the data source in Spring’s context file. If you remember the basic steps of JDBC Connection in Java, first we load the driver using Class.forName(), then getting connection using DriverManager providing the URL such as Connection con = DriverManager.getConnection(, ,) and then using Statement or PreparedStatement. While configuring the DataSource in Spring we may need to pass connection details (such as DriverName, URL, Username, Password) to Spring framework. The benefit of configuring data sources in this way is that they can be managed completely external to the application, leaving the application to simply ask for a data source when it’s ready to access the database.
- 6. 1. Driver Based Data Source It is the simplest data source that can be configured in Spring. This should not be used in Production but it is good to use in Development Environment for unit testing. There are Two data source classes. • DriverManagerDataSource • SingleConnectionDataSource The basic difference is DriverManagerDataSource provides a new connection each time, where as SingleConnectionDataSource provides the same connection. Let’s see an example, to connect MySQL database I am using com.mysql.jdbc.Driver class. And don’t need any username or password. We use DriverManagerDataSource so the configuration would be:
- 7. <bean id=”MyDataSource” class=”org.springframework.jdbc.datasource.DriverManagerDataSource”> <property name=”driverClassName” value=”com.mysql.jdbc.Driver”/> <property name=”url” value=”jdbc:mysql://localhost/test”/ > <property name=”username” value=””/> <property name=”password” value=””/> </bean>
- 8. How it is if we take the connection details (Driver class name, url, username, password etc. ) from a property file rather than defining in Spring Context XML file itself? Yes, it is a good idea to take the database connection details from a property file. So let’s create a property file. We will name the file as: jdbc.properties
- 9. You need this extra entry to include the properties from jdbc.properties file. Properties define in jdbc.properties file
- 10. 2. JNDI (Java Naming and Directory Interface) DATA SOURCE Application server are often pooled for greater performance. The application servers such as WebSphere, WebLogic, Jboss allow to configure connection pools. And these connection pools can be retrieved through a JNDI. The benefit of configuring data sources in this way is that they can be managed completely external to the application, leaving the application to simply ask for a data source when it’s ready to access the database. In driver based data source, we saw any of the 2 classes DriverManagerDataSource and SingleConnectionDataSource can be used to establish the connection. Similarly for JNDI data source, we use JndiObjectFactoryBean.
- 11. I have created a connection pool my application server. The JNDI name is “mysqldatasource”. There is a servlet deployed in the same Server which gets the DAO object from the Spring Container. Spring provided the dataSource to the DAO after getting connection from the connection-pool mysqldatasource.
- 12. 3. Pooled Data Source If you’re unable to retrieve a data source from JNDI, the next best thing is to configure a pooled data source directly in Spring. Spring doesn’t provide a pooled data source, there’s a suitable one available in the Jakarta Commons Database Connection Pools (DBCP) project. To add DBCP to your application, you need to download the JAR file and place it into your build path along with spring library files. The class you do use for Pooled Data Source is : org.apache.commons.dbcp.BasicDataSource
- 13. Two new properties in Pooled Data Source
- 14. Step 2: Configure JDBC Template After configuring the DataSource, the next step is configuring the JDBCTemplate. The JdbcTemplate class is the central class in the JDBC core package. It simplifies the use of JDBC since it handles the creation and release of resources. This helps to avoid common errors such as forgetting to always close the connection. It executes the core JDBC workflow like statement creation and execution, leaving application code to provide SQL and extract results. This class executes SQL queries, update statements or stored procedure calls, imitating iteration over ResultSets and extraction of returned parameter values. It also catches JDBC exceptions and translates them to the generic, more informative, exception hierarchy defined in the org.springframework.dao package.
- 15. Option 1: The JdbcTemplate can be used within a DAO implementation via direct instantiation with a DataSource reference OR Option 2: be configured in a Spring IOC container and given to DAOs as a bean reference. Option 1: Explanation The JdbcTemplate within a DAO implementation via direct instantiation with a DataSource reference.
- 16. Option 2: Explanation Configured in Spring IOC container and given JdbcTemplate to DAOs as a bean reference.
- 18. Step 3: Writing DAO Layer We already discussed that the JdbcTemplate can be used within a DAO implementation via direct instantiation with a DataSource reference OR be configured in a Spring IOC container and given to DAOs as a bean reference. Now we will see how they can be implemented in the DAO class. Option 1: The JdbcTemplate within a DAO implementation via direct instantiation with a DataSource reference.
- 19. We are injecting DataSource but not JDBCTemplate In DAO Class Created JDBCTemplate instance and assign to localobject Using JDBCTemplate
- 20. Option 2: Configured in Spring IOC container and given JdbcTemplate to DAOs as a bean reference. Explanation : In all our examples, we adopted this option only…
- 21. In DAO Class Bean id must be JDBCTemplate JDBCTemplate not DataSource