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A typical J2EE application may contain Enterprise JavaBeans or EJBs. These beans contain the application's business logic and live business data. Although it is possible to use standard Java objects to contain your business logic and business data, using EJBs addresses many of the issues of using simple Java objects, such as scalability, lifecycle management and state management.
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- Session Beans implementation analysis
- Sample application
- The JBoss environment
- The Geronimo environment
- Step-by-step migration
- Summary
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EJB implementation analysis
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EJB implementation may vary from one vendor to another. The purpose of this section is to provide a session bean specific feature-to-feature comparison between JBoss and Apache Geronimo so you can clearly identify the differences and plan accordingly before migration.
Feature | JBoss v4 | Apache Geronimo (OpenEJB) |
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Stateful and stateless Session Beans | supported | supported |
BMP (Bean Managed Persistence) Entity Beans | supported | supported |
CMP (Container Managed Persistence) Entity Beans | supported | supported |
Message driven beans (MDBs) | supported | supported |
Interoperability using RMI-IIOP or JAXRPC | supported | supported |
Ability to expose stateless session beans and MDBs as Web Services | supported | supported |
Support for sending and receiving messages via Web Services | supported | supported |
Easy provisioning and hot deployment of EJB and JMX-based Web Services | supported | supported |
Access to EJBs from external CORBA objects | supported | supported |
Sample application
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This sample application Session Bean Sample Application shows how session beans are used and deployed in a container. There are two clients, one for stateless session beans and another for stateful session beans. Both client applications use the same database which contains a table that stores loan application details. An entity bean is used to connect to and operate on the loan details table. A session bean is then used by the client application to get specific details from the database using the entity bean. The first client creates a stateless session bean and displays a list of denied loan applications via a method defined in that EJB. The second client creates a stateful session bean and adds loan applications to the database.
The following figure illustrates the application flow:
Application Beans
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Download the Session Bean sample application from the following URL:following link:
Session Bean Samplehttp://opensource2.atlassian.com/confluence/oss/download/attachments/1155/session.zip
After extracting the zip file, a session directory will be created. From now on, this directory will be referred as <session_home>.
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This will compile the source files and package the EJB jar file. You can see the results in the <session_home>/target directory. The following list shows the dependency jars needed in building and running the Session Bean sample application.
- geronimo-spec-ejb-_2.1_spec-rc41.0.jar - the EJB spec; needed for compiling source.
- openejb-core-2.0-G1M5.jar - needed by Geronimo during runtime.
- geronimo-spec-j2ee-_1.4_spec-rc41.0.jar - needed by Geronimo during runtime.
- geronimo-security-1.0-M5.jar - needed by Geronimo during runtime.
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The following figures illustrate the home page for the Web Application as well as the testing for the stateless and stateful beans depending on your selection on the Web Application home page.
The Geronimo environment
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CREATE 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)
Step-by-step migration
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<openejb-jar xmlns="http://www.openejb.org/xml/ns/openejb-jar" xmlns:naming="http://geronimo.apache.org/xml/ns/naming" xmlns:security="http://geronimo.apache.org/xml/ns/security" xmlns:sys="http://geronimo.apache.org/xml/ns/deployment" configId="geronimo/SessionBeanDemo/1.0/car" parentId="orggeronimo/apache/geronimo/Serverj2ee-server/1.0/car"> <enterprise-beans> <entity> <ejb-name>CustomerEJB</ejb-name> <jndi-name>CustomerHomeRemote</jndi-name> <local-jndi-name></local-jndi-name> <resource-ref> <ref-name>jdbc/ibm-demo</ref-name> <resource-link>SystemDatasource</resource-link> </resource-ref> </entity> <session> <ejb-name>LoanManagerEJB</ejb-name> <jndi-name>LoanManagerHomeRemote</jndi-name> <ejb-ref> <ref-name>ejb/CustomerHomeRemote</ref-name> <ejb-link>CustomerEJB</ejb-link> </ejb-ref> </session> <session> <ejb-name>StatefulLoanManagerEJB</ejb-name> <jndi-name>StatefulLoanManagerHomeRemote</jndi-name> <ejb-ref> <ref-name>ejb/CustomerHomeRemote</ref-name> <ejb-link>CustomerEJB</ejb-link> </ejb-ref> </session> </enterprise-beans> </openejb-jar> |
As with all Geronimo deployment plans, this configuration requires a parent configuration. In this case, it is orggeronimo/apache/geronimo/Serverj2ee-server/1.0/car, then follows the definition of the EJBs.
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As with JBoss, the following figures illustrate the home page for the Web Application as well as the testing for the stateless and stateful beans depending on your selection on the Web Application home page.
Summary
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This article has shown how to migrate a sample application that uses Session Beans, from JBoss v4.0.2 to Apache Geronimo M5. This article provided step-by-step instructions to build the application, deploy and run it, and then migrate it to the Geronimo environment.
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