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JDBC resource lookup from EJB

Friday Oct 26, 2007

Accessing a JDBC resource from an EJB is a fairly simple thing to do. As simple as the following:

1. Start domain and database

After installing GlassFishV2, start the domain domain1 and start the database. I would be using Derby in this example. Derby can be started in 2 ways

<INSTALL_ROOT>/bin/asadmin start-database
From netbeans : Tools -> Java DB Database -> Start JavaDB Server. The port settings for the server started up can be modified in ~/.netbeans-derby/derby.properties

Now, the database is started at port :1527 and domain is running at 4848.

2. Create a JDBC Connection pool and JDBC Resource

Login to the Admin Console (http://localhost:4848) and navigate to Resources->JDBC->ConnectionPools. Click on New and enter the details like Name:Cacti ResourceType:javax.sql.DataSource DatabaseVendor:Derby. In the next screen, accept the default values but don't forget to enter the following additional properties

DatabaseName : sampleDB
ConnectionAttributes : create=true (if the sampleDB does not exist)
Password : dbpassword
PortNumber : 1527 (or the customized DB port)
ServerName : localhost
User : dbuser

Click on Finish. To verify, click on the 'Cacti' connection pool you just created and do a 'Ping connection Pool".

Navigate to Resources->JDBC->JDBCResource on the left panel of the admin console and click on New. Specify a JNDI name as "jdbc/cactus". I chose to append the name cactus with jdbc since i am accessing a database. Choose the pool name you just created "Cacti" and click on 'OK'.

3. Access the resource in your app

Suppose i have an EJB that has to use this JDBC resource. This can be done as follows in the SampleEjb.java : test() method

InitialContext ic = new InitialContext();
DataSource ds = (javax.sql.DataSource) ic.lookup("jdbc/cactus"

Connection con = ds.getConnection();

insert("something", ...., con);

con.close();

Create the appropriate Remote and Home interfaces.

4. Specifying the appropriate deployment descriptors:

Consider this is a web application.

application.xml

<application>
    <display-name>Sample EJB Test</display-name>
    <module>
            <web>
                <web-uri>sample-test.war</web-uri>
                <context-root>/sample-test</context-root>
            </web>
    </module>
    <module>
            <ejb>sample-test.jar</ejb>
    </module>
</application>

ejb-jar.xml

<ejb-jar>
    <description>Sample test</description>
    <display-name>Sample test </display-name>
<enterprise-beans>
      <session>
          <description> Sample bean </description>
          <display-name> Sample bean </display-name>
          <ejb-name>SampleRemote</ejb-name>
          <home>examples.SampleRemoteHome</home>
          <remote>examples.SampleRemote</remote>
          <ejb-class>examples.SampleEjb</ejb-class>
          <session-type>Stateless</session-type>
          <transaction-type>Bean</transaction-type>
      </session>
</enterprise-beans>
</ejb-jar>

sun-ejb-jar.xml

<sun-ejb-jar>
        <enterprise-beans>
                <ejb>
                        <ejb-name>SampleRemote</ejb-name>
                        <jndi-name>SampleRemote</jndi-name>
                </ejb>
        </enterprise-beans>
</sun-ejb-jar>

web.xml

<web-app>
    <distributable/>
    <servlet>
        <servlet-name>SampleTestServlet</servlet-name>
        <display-name>Sample Test Servlet</display-name>
        <servlet-class>servlets.SampleTestServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>SampleTestServlet</servlet-name>
        <url-pattern>/SampleTestServlet</url-pattern>
    </servlet-mapping>
</web-app>

5. After all this coding, the structure would look like

/opt/sample
           -src
                -examples.SampleEjb
                -examples.SampleRemoteHome
                -examples.SampleRemote
                -servlets.SampleTestServlet
           -descriptor
                -ear
                    -application.xml
                -jar
                    -ejb-jar.xml
                    -sun-ejb-jar.xml
                -web
                    -web.xml
           -web
                 -index.jsp
           -build.xml