The Program Directory Structure

Below is the program directory structure for the BankClient application which invokes the BankServiceBean in order to add the Customer entity to the database.

There are a couple of differences in the directory structure from the one described in the previous chapter. We have added an entity subdirectory; this contains the entity source code, Customer.java. We have also added a config subdirectory containing the manifest.mf and persistence.xml files.

Building the Application

Because we are persisting entities from an EJB container we need to place the persistence.xml file in the META-INF directory within the EJB module, BankService.jar. The package-ejb target in the Ant build file does this:

<target name="package-ejb" depends="compile">
<jar jarfile="${build.dir}/BankService.jar">
<fileset dir="${build.dir}">
<include name="ejb30/session/**" />
<include name="ejb30/entity/**" />
</fileset>
<metainf dir="${config.dir}">
<include name="persistence.xml" />
</metainf>
</jar>
</target>

We can use the jar -tvf command to examine the contents of the JAR file:

C:\EJB3Chapter03\glassfish\lab1\build>jar -tvf BankService.jar
...META-INF/
...META-INF/MANIFEST.MF
...ejb30/
...ejb30/entity/
...ejb30/session/
...ejb30/entity/Customer.class
...ejb30/session/BankService.class
...ejb30/session/BankServiceBean.class
...META-INF/persistence.xml

This is only one of a number of ways to package the persistence unit. Entities can be persisted not only from an EJB container but also from a web container or from a Java SE application running outside the container. We shall see an example of Java SE persistence in Chapter 6. Consequently the persistence unit (entity classes together with the persistence.xml file) can be placed in WEB-INF/classes directory of a WAR file or in a Java SE application client jar file.

Alternatively we can package a persistence unit into a separate jar file. This jar file can then be added to the WEB-INF/lib directory of a WAR file, the root of an EAR file or in the library directory of an EAR file. Adding a persistence unit to a Java EE module limits its scope to that module. If we place the persistence unit in an EAR it is visible to all modules within the application.

In our example we want the database tables to be created at deploy time, and dropped when we undeploy an application from the container. We modify the deploy target in our Ant build file, adding a createtables=true clause:

<target name="deploy">
<exec executable="${glassfish.home}/bin/asadmin"
failonerror="true"
vmlauncher="false">
<arg line="deploy --user admin --passwordfile
adminpassword --createtables=true
${build.dir}/BankService.ear"/>
</exec>
</target>

Similarly we add a droptables=true clause for the undeploy target.

<target name="undeploy">
<exec executable="${glassfish.home}/bin/asadmin"
failonerror="true"
vmlauncher="false">
<arg line="undeploy --user admin --passwordfile
adminpassword --droptables=true BankService"/>
</exec>
</target>

Note that before we can deploy BankService within GlassFish, we need to start up the embedded Derby database. We do this from the command-line with the asadmin utility:

C:\> asadmin start-database