Avitek Medical Records Development Tutorials

Developing the MedRec Applications

Tutorial 10: Using EJBGen to Generate EJB Deployment Descriptors

This tutorial demonstrates how to use the WebLogic Server EJBGen utility to generate deployment descriptor files (ejb-jar.xml and weblogic-ejb-jar.xml) and EJB source files, such as the Home interface file, from the main programmer-written EJB bean source file that contains your business logic. In particular, this tutorial uses the PhysicianSession EJB from the physicianEar application.

EJBGen uses JDK 5.0 metadata annotations in the bean file to generate the deployment descriptor files and the supporting EJB Java source files, such as the Home and Remote interfaces. This means that you only need to program one file that contains your business logic, and use EJBGen-specific annotations inside this file to specify the shape and behavior of the EJB. The EJBGen utility then takes care of generating all supporting files.

The wlcompile Ant task automatically invokes the EJBGen utility if it encounters a Java file with a *.ejb extension, instead of the normal *.java extension. This means that you can mix EJBGen-annotated files with standard Java files in an EAR structure and use a single wlcompile Ant task to compile all the code.

All EJB files in the MedRec application are already annotated with EJBGen metadata annotations.

The tutorial includes the following sections:

Prerequisites

Before starting this tutorial, complete Tutorial 9: Deploying MedRec from the Development Environment so that you have already compiled the physicianEar application, started the MedRec server, and deployed the application, including its EJBs.

If you completed up to Tutorial 5 but skipped one or more of the subsequent tutorials so that you have not yet deployed the physicianEar application, you can catch up by moving to the c:\medrec_tutorial\src\physicianEar subdirectory, setting the environment, and using Ant to run the default build.xml file to build the entire application and deploy it to WebLogic Server:

prompt> c:\bea\user_projects\domains\MedRecDomain\bin\setDomainEnv.cmd

prompt> cd c:\medrec_tutorial\src\physicianEar

prompt> ant -f build.xml build deploy.physician.ear

Procedure

In the following steps you use the Administration Console to view administrative information about a deployed EJB; view the EJB Java source file that contains the EJBGen metadata annotations; view some of the files that EJBGen generates, and finally use EJBGen to regenerate those files.

Step 1: Use the Administration Console to view information about a deployed EJB.

The procedure is not necessary for using EJBGen; it is provided only as additional information about using the Administration Console to view a deployed EJB.

Step 2: View the EJB bean class file that contains the EJBGen metadata annotations.

See EJBGen Reference for additional information about EJBGen and the full list of annotations.

Step 3: View the already-generated deployment descriptor and Java files.

In Tutorial 7: Compiling Split Development Directory Applications with Ant Tasks, you executed the wlcompile Ant task, which in turn executed the EJBGen utility to compile the EJBs of the physicianEar application. This procedure describes how to view the deployment descriptor files and supporting Java interfaces that were generated by EJBGen, located in the \build directory.

Step 4: Use the EJBGen utility to regenerate the deployment descriptor and EJB files.

When you program EJBs using annotations within a split development directory structure, you typically only need to execute the wlcompile Ant task over the entire source directory to compile the EJB and generate its supporting files into the build directory. As long as the EJB files that use annotations have the *.ejb extension, the wlcompile Ant task automatically knows to execute the EJBGen Ant task on the file.

You can, however, also use the EJBGen utility on its own if you want to generate the EJB deployment descriptors and supporting home and remote interfaces individually, outside of the wlcompile Ant task. You can execute the EJBGen utility using either of the following methods:

The following procedure shows how to use the Ant task.

Best Practices

Use EJBGen to develop the EJB component of your application. You can simplify your EJB development and code maintenance by writing just the bean implementation files and annotating them with EJBGen metadata annotations, and then generating all the remaining files—the home interface, the local interface, the deployment descriptor files—using EJBGen.

The Big Picture

The scripts that compile and deploy MedRec use EJBGen to generate most of the EJB files in the application. The EJBGen task is called implicitly by the wlcompile task any time wlcompile encounters a file with the *.ejb extension.

The PhysicianSessionEJB.ejb Java file contains all of the information necessary for EJBGen to generate the EJB descriptor files and the home interface. You can view the EJBGen annotations by opening C:\medrec_tutorial\src\physicianEar\physSessionEjbs\com\bea\medrec\controller\PhysicianSessionEJB.ejb in an IDE or text editor.

For example, the following class-level @weblogic.ejb.Session annotation specifies that the class implements a stateless session EJB, and then defines the pool and timeout settings that you see in the generated weblogic-ejb-jar.xml:

@Session(maxBeansInFreePool = "1000",
         initialBeansInFreePool = "0",
         transTimeoutSeconds = "0",
         type = Session.SessionType.STATELESS,
         defaultTransaction = Constants.TransactionAttribute.REQUIRED,
         enableCallByReference = Constants.Bool.TRUE,
         ejbName = "PhysicianSessionEJB")
public class PhysicianSessionEJB extends GenericSessionBean {

...

Troubleshooting

The RecordEJB entity bean is hard-coded to use the Pointbase database. This means that if you want the Medrec application to use a database other than Pointbase, such as Oracle or MySQL, you must change the source code of the RecordEJB entity bean accordingly, in addition to changing the JDBC data sources (both global and application-scoped) to point to the new database.

The source code for the RecordEJB entity bean is located in the following EJBGen file:

C:\medrec_tutorial\src\medrecEar\entityEjbs\com\bea\medrec\entities\RecordEJB.ejb

Use of the Pointbase database is hard-coded with the databaseType attribute of the @weblogic.ejb.Entity metadata annotation, as shown by the following code excerpt (relevant section in bold):

@Entity(maxBeansInCache = "1000",
        dataSourceName = "jdbc/MedRecTxDataSource",
        transTimeoutSeconds = "0",
        ejbName = "RecordEJB",
        reentrant = Constants.Bool.FALSE,
        concurrencyStrategy = Constants.ConcurrencyStrategy.DATABASE,
        delayDatabaseInsertUntil = Entity.DelayDatabaseInsertUntil.EJB_POST_CREATE,
        tableName = "record",
        readTimeoutSeconds = "600",
        primKeyClass = "java.lang.Integer",
        defaultTransaction = Constants.TransactionAttribute.MANDATORY,
        abstractSchemaName = "RecordEJB",
        databaseType = Entity.DatabaseType.POINTBASE)

To specify an Oracle database, for example, change the value of the databaseType attribute to Entity.DatabaseType.ORACLE.

See weblogic.ejbgen.Entity for all valid values for the databaseType attribute.

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