Overview

An entity bean is defined as a representation of persistent data that has the ability to read from database and populate its fields with data. It can be updated and stored back to the database. There are two types of entity beans: Bean-Managed Persistence(BMP) and Container-Managed Persistent(CMP). This article covers an example of a CMP, more specifically, a CMP application migration. For this type of entity bean, actual code must be written to handle persistent operations such as loading, saving and finding data. The developer must use persistence API such as JDBC to select, insert, update, delete from a database.

This article is organized in the following sections:

• CMP implementation analysis
• Sample application
• The JBoss environment
• The Geronimo environment
• Step-by-step migration
• Summary

CMP implementation analysis

CMP implementation may vary from one vendor to another. The purpose of this section is to provide a CMP specific feature-to-feature comparison between JBoss v4 and Apache Geronimo M5 so you can clearly identify the differences and plan accordingly before migration.

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Sample application

The Loan CMP application is very simple. When the command line client is run, an entry is made into the database. The findByPrimaryKey() method of the CustomerHomeRemote interface is called and the field values of the returned CustomerRemote object are printed to the console. This is followed by a call to the findBySssNo() method after which the field values of the returned CustomerRemote object are printed to the console.

The following figure illustrates the application flow:

The user runs the command line client which then either creates an entity bean (which then adds itself to the datasource) or asks for one, by primary key, which is created from information that is stored in the database.

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Application Beans

The Loan CMP application consists of the following packages:

• com.ibm.demo.entity.client
  • CMPClient
    • contains the main class that is called from the console.
• com.ibm.demo.entity.bmp
  • CustomerBean
    • implements javax.ejb.EntityBean
    • fields of the bean are defined here
    • contains business methods corresponding to the methods exposed by the CustomerRemote interface.
    • Conatins callback methods that are called by the container to manage the bean. These methods include the create and find methods which use jdbc to make entries to the database and to search the database.
    • Has a helper method that looks up the datasource through jndi.
  • CustomerRemote
    • interface that extends javax.ejb.EJBObject
    • exposes the setter and getter methods of the EJB
  • CustomerHomeRemote
    • interface that extends javax.ejb.EJBHome
    • exposes the create and find methods of the EJB

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Tools used

The tools used for developing and building the Loan CMP sampple application are:

Eclipse

The Eclipse IDE was used for development of the sample application. This is a very powerful and popular open source development tool. Integration plug-ins are available for both JBoss and Geronimo. Eclipse can be downloaded from the following URL:

http://www.eclipse.org

Apache Maven

Maven is a software project management and comprehension tool. Based on the concept of a project object model (POM). Maven can manage a project's build, reporting and documentation from a central piece of information.

For this migration example Maven 1.0.2 was used. Maven can be downloaded from the followinf URL:

http://maven.apache.org

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Sample database

The sample database for the Loan CMP application has only one table. This is an in-memory table. The MEMORY storage engine creates tables with contents that are stored in just in memory. These were formerly known as HEAP tables.

The following table describes the fields of the CUSTOMER table.

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The JBoss environment

This section shows you how and where the sample JBoss reference environment was installed so you can map this scenario to your own implementation. Note that for this migration example JBoss v4.0.2 was used.

Detailed instructions for installing, configuring, and managing JBoss are provided in the product documentation. Check the product Web site for the most updated documents.

The following list highlights the general tasks you will need to complete to install and configure the initial environment as the starting point for deploying the sample application.

1. Download and install JBoss v4 as explained in the product documentation guides. From now on the installation directory will be referred as <jboss_home>
2. Create a copy of the default JBoss v4 application server. Copy recursively <jboss_home>\server\default to <jboss_home>\server\<your_server_name>
3. Start the new server by running the run.sh -c <your_server_name> command from the <jboss_home>\bin directory.
4. Once the server is started, you can verify that it is running by opening a Web browser and pointing it to this URL: http://localhost:8080. You should see the JBoss Welcome window and be able to access the JBoss console.
5. Once the application server is up and running, the next step is to install and configure all the remaining prerequisite software required by the sample application. This step is described in the following section.

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Install and configure prerequisite software

In order to build and run the Loan CMP application included in this article, you need to install and configure the build tool and the database that is used by the application.

Modify database settings

This application is using the HSQL database that comes as part of the JBoss bundle. You need to modify the script for creating the database. Edit the localDB.script file located in the following directory:

<jboss_home>\server\<your_server_name>\data\hypersonic

Add at the top of the localDB.script file the content of the following example in order to create the sample HSQL database.

CREATE MEMORY TABLE CUSTOMER(ID INTEGER NOT NULL PRIMARY KEY,NAME VARCHAR(45),BIRTHDATE DATE,SSS_NO VARCHAR(25),ADDRESS VARCHAR(60),ANNUAL_SALARY DOUBLE,LOAN_AMOUNT DOUBLE)

Configure Maven

As mentioned before, Apache Maven is used to build the binaries for the Loan CMP application. If you do not have Maven installed this is a good time for doing it.

Apache Maven can be downloaded from the following URL:

http://maven.apache.org

Build the sample application

In order to build the loan application a Maven script has been provided. Download the Loan application from the following URL:

http://opensource2.atlassian.com/confluence/oss/download/attachments/1146/cmp.zip

After extracting the zip file, a loan-cmp directory will be created. From now on, this directory will be referred as <cmp_home>. In that directory open the project.properties file. Edit the maven.jboss.home property to match your environment. It is important that you use "//" on the windows platform as is done below.

maven.jboss.home=Z://JBoss-4.0.2

From a command prompt or shell go to the <cmp_home> directory and run the following command:

maven

This will build a jar and a war file and put them in the <cmp_home>/target folder. The jar created by the Maven build contains a JBoss specific deployment descriptor, the jboss.xml file in located the META-INF directory of the JAR is shown in the following example:

<?xml version="1.0"?>

<jboss>
   <enterprise-beans>
      <entity>
         <ejb-name>CustomerEJB</ejb-name>
         <jndi-name>CustomerHomeRemote</jndi-name>
      </entity>
   </enterprise-beans>
</jboss>

The jndi-name element is used to bind the CustomerEJB to the name CustomerHomeRemote in JNDI.

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The Geronimo environment

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Step-by-step migration

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Summary

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