Exercise 6.2: @IdClass

Exercise 6.2: @IdClass

This exercise shows you an example of using @javax.persistence.IdClass to map a primary key class to the database.

Start Up JBoss

If you already have JBoss running, there is no reason to restart it. Otherwise, start it up as instructed in Workbook 1.

Initialize the Database

The database tables will be created when Exercise 6.2 is deployed to JBoss. If you have problems running this example, shut down JBoss and run the clean.db Ant task.

Build and Deploy the Example Programs

Perform the following steps:

As in the last exercise, titan.jar is rebuilt, copied to the JBoss deploy directory, and redeployed by the application server.

Examine the Example Files

The Customer entity code was a cut-and-paste from the @IdClass section of Chapter 6, so it needs no further explanation. TRavelAgentBean again acts as a simple data access object, wrapping invocations around the EntityManager instance injected into this EJB. The Client application simply allocates a Customer entity and then calls createCustomer( ) and findCustomer( ) on TRavelAgentBean to insert and find the Customer in the database.

Run the Client

Run the Client application by invoking ant run.client at the command prompt. Remember to set your JBOSS_HOME and PATH environment variables. This is the output:

run.client:
     [java] Bill
     [java] Burke
     [java] 9999999