Chapter 24. Exercises for Chapter 6

Exercise 6.1: Basic Persistence in CMP 2.0

This exercise begins walking you through the intricacies of CMP 2.0. In this chapter, you will learn more detailed JBoss CMP 2.0 configuration mechanisms by creating the Customer EJB described in the EJB book.

Start Up JBoss

If you already have JBoss running, there is no reason to restart it. Otherwise, start it up as instructed in the JBoss Installation and Configuration chapter.

Initialize the Database

The database table for this exercise will automatically be created in JBoss’s default database, HypersonicSQL, when the EJB JAR is deployed.

Build and Deploy the Example Programs

Perform the following steps:

  1. Open a command prompt or shell terminal and change to the ex06_1 directory created by the extraction process

  2. Set the JAVA_HOME and JBOSS_HOME environment variables to point to where your JDK and JBoss 4.0 are installed. Examples:

    Windows: C:workbookex06_1> set JAVA_HOME=C:jdk1.4.2 C:workbookex06_1> set JBOSS_HOME=C:jboss-4.0
    Unix: $ export JAVA_HOME=/usr/local/jdk1.4.2 $ export JBOSS_HOME=/usr/local/jboss-4.0

  3. Add ant to your execution path.

    Windows: C:workbookex06_1> set PATH=..antin;%PATH%
    Unix: $ export PATH=../ant/bin:$PATH

  4. Perform the build by typing ant.

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

Examine the JBoss-Specific Files

In this section, we introduce a new JBoss CMP 2.0 deployment descriptor, jbosscmp-jdbc.xml. This file provides more detailed control of your bean’s database mapping as well as more advanced performance-tuning options.

jbosscmp-jdbc.xml

<jbosscmp-jdbc>

   <defaults>
      <datasource>java:/DefaultDS</datasource>
      <datasource-mapping>Hypersonic SQL</datasource-mapping>
      <create-table>true</create-table>
      <remove-table>true</remove-table>
   </defaults>

   <enterprise-beans>
      <entity>
         <ejb-name>CustomerEJB</ejb-name>
         <table-name>Customer</table-name>
         <cmp-field>
            <field-name>id</field-name>
            <column-name>ID</column-name>
         </cmp-field>
         <cmp-field>
            <field-name>lastName</field-name>
            <column-name>LAST_NAME</column-name>
         </cmp-field>
         <cmp-field>
            <field-name>firstName</field-name>
            <column-name>FIRST_NAME</column-name>
         </cmp-field>
         <cmp-field>
            <field-name>hasGoodCredit</field-name>
            <column-name>HAS_GOOD_CREDIT</column-name>
         </cmp-field>
      </entity>
   </enterprise-beans>
</jbosscmp-jdbc>

The <defaults> section

The <datasource> configuration variable tells JBoss’s CMP engine what database connection pool to use for the entity beans defined in this JAR.

<datasource>java:/DefaultDS</datasource>

It is currently configured to use the default data source defined in $JBOSS_HOME/server/default/deploy/hsqldb-service.xml, but you can change it to your own defined data sources. The workbook’s Appendix goes into more detail on how to configure your own data sources.

This variable describes the database mapping that CMP should use:

<datasource-mapping>Hypersonic SQL</datasource-mapping>

Here are some other mappings you could use (this list is not exhaustive):

<datasource-mapping>Oracle8</datasource-mapping>
<datasource-mapping>Oracle7</datasource-mapping>
<datasource-mapping>MS SQLSERVER</datasource-mapping>
<datasource-mapping>MS SQLSERVER2000</datasource-mapping>

For other available supported database mappings, please review JBoss’s advanced documentation on its web site at http://www.jboss.org.

When the <create-table> configuration variable is set to true, JBoss creates the database tables for each entity bean defined in the deployment descriptor unless these tables already exist. This create action is triggered when the EJB JAR is deployed:

<create-table>true</create-table>

When the <remove-table> configuration variable is set to true, JBoss drops the database tables for each entity bean defined in the deployment descriptor. This remove action is triggered when the EJB JAR is redeployed or undeployed:

<remove-table>true</remove-table>

The <enterprise-beans> section

There’s an XML fragment <entity></entity> for each entity bean defined in this EJB JAR. The <ejb-name> variable defines the entity bean that is described in that section:

<ejb-name>CustomerEJB</ejb-name>

The <table-name> variable defines what database table this entity bean should map to:

<table-name>Customer</table-name>

Each <cmp-field> section describes the mapping between an entity bean’s fields and the corresponding columns of the database table. The <field-name> tag is the entity bean field’s name, while the <column-name> defines the table column’s name:

<cmp-field>
     <field-name>id</field-name>
     <column-name>ID</column-name>
  </cmp-field>

Examine and Run the Client Applications

There is only one client application for this exercise, Client_61. It is modeled after the example in the EJB book. It creates Customer EJBs in the database based on the command-line parameters.

To run the client, first set your JBOSS_HOME and PATH environment variables appropriately. Then invoke the provided wrapper script to execute the program. For each customer, you must supply on the command line a set of values for primary key, first name, and last name, as shown here:

Client_61 777 Bill Burke 888 Sacha Labourey

The output of this execution should be:

C:workbookex06_1>client_61 777 Bill Burke 888 Sacha Labourey
Buildfile: build.xml

prepare:

compile:

ejbjar:

run.client_61:
     [java] 777 = Bill Burke
     [java] 888 = Sacha Labourey

When it finishes, the example program removes the created beans, so no data remains in the database.

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