Documentation : JBoss to Geronimo - EJB-Session Beans Migration
This page last changed on Dec 14, 2005 by hcunico@gmail.com.
OverviewA 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. This document discusses one type of EJB, the Session EJB. This type of EJB is useful for mapping business process flow (or equivalent application concepts). There are two types of Session EJB, stateless and stateful. EJBs hold conversations with clients. A conversation is basically an interaction between the EJB and the client and these interactions are composed of method calls by the clients to the EJBs. Stateful session beans retain state on behalf of a client. This means that if the state of the bean changes during a client's method call, this state is retained for subsequent calls by the same client. A stateless session bean on the other hand retains no conversational state from method to method. In other words, it is expected to hold its conversational state for only a single method call. This article is organized in the following sections:
EJB implementation analysisEJB 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.
Sample applicationThis 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 BeansThe session bean sample application consists of the following packages:
Tools usedThe tools used for developing and building all the applications are: Eclipse with JBoss IDEThe Eclipse with JBoss IDE plug-ins was used for development of Java-source code of the sample applications. Eclipse is a very powerful and popular open source development tool. Eclipse can be downloaded from the following URL: Apache MavenMaven 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: Sample databaseThe sample database for the MDB sample 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.
The JBoss environmentThis 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.
Install and configure prerequisite softwareIn order to build and run the Session Bean sample 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 settingsThis 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 MavenAs mentioned before, Apache Maven is used to build the binaries for the Session Bean sample 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: Download the sample applicationDownload the Session Bean sample application from the following link: After extracting the zip file, a session directory will be created. From now on, this directory will be referred as <session_home>. Set the JNDI propertiesOpen the jndi.properties file located in the <session_home>/jndi directory. Make sure that every property under the JBoss Settings section are uncommented and every property under the Geronimo Settings are commented out. jndi.properties #################################################################### ### JBoss Settings #################################################################### java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces java.naming.provider.url=localhost #################################################################### ### Geronimo Settings #################################################################### #java.naming.factory.initial=org.openejb.client.RemoteInitialContextFactory #java.naming.provider.url=localhost:4201 #java.naming.security.principal=username #java.naming.security.credentials=passwd Verify the WAR filesOpen the web.xml file located in the <session_home>/src/webapp/WEB-INF directory and make sure the following taglib element is not commented out. Excerpt from the web.xml file ... <taglib> <taglib-uri>http://java.sun.com/jstl/core</taglib-uri> <taglib-location>/WEB-INF/tld/c.tld</taglib-location> </taglib> ... Open the two jsp files, stateless.jsp and stateful.jsp located in the <session_home>/src/webapp directory and make sure the following line is present: <%@ taglib prefix="c" uri="http://java.sun.com/jstl/core" %> Build the sample applicationIn order to build the Session Bean sample application a Maven build script has been provided. Open a command line and change directory to <session_home>, in that directory open the project.properties file. Edit the maven.jboss.home property to match your environment. build.properties maven.ejb.includes=com/ibm/demo/entity/**, com/ibm/demo/session/** maven.ejb.excludes=com/ibm/demo/client/** maven.ejb.src=dd maven.jboss.home=<jboss_home> maven.geronimo.home=<geronimo_home>
From a command prompt or shell go to the <session_home> directory and run the following command: maven ejb war 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.
Deploy the sample applicationTo deploy the Session Bean sample application you just built with Maven, copy the session-ejb-SNAPSHOT.jar and session-ejb.war files from the <session_home>/target directory to the following directory: <jboss_home>\server\<your_server_name>\deploy If JBoss is already started, it will automatically deploy and start the applications; otherwise, the applications will be deployed and started at the next startup. Test the sample applicationTo test the Session Bean sample application run the following commands from the <session_home> directory: maven run:stateless - for the stateless client The following example shows the results of the stateless session client.
The following example shows the results of the stateful session client.
If you run the stateless client again you will see now some customers with a denied loan application.
You can also run the webapp client by opening a browser window and going to the following URL: 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 environmentDownload and install Geronimo from the following URL: http://geronimo.apache.org/downloads.html The release notes available there provide clear instructions on system requirements and how to install and start Geronimo. Throughout the rest of this article we will refer to the Geronimo installation directory as <geronimo_home>.
Configure resourcesFor this scenario the Session Bean application will use directly the SystemDatabase from Geronimo. In this case there is no need to set up a new connector for the SystemDatabase since it is already configured as the DefaultDatasource. Start the Geronimo serverEnsure that Geronimo is up and running. If the server has not been started yet, do so by typing the following command: <geronimo_home>/bin/startup.sh Once the server is started you should see a screen similar as the one illustrated in the following example:
Configure database via Geronimo ConsoleAccess the Geronimo Console by pointing your Web browser to the following URL: Enter system as the username and manager as the password, click Login. Once logged in, on the bottom left corner from the left navigation panel click on DB Manager. In the text area labeled SQL Command/s enter the following SQL statement and click Run SQL; this will create the table used by the Session Bean. 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 migrationWhen you built the Session Bean sample application, Maven packaged the deployment descriptors for both JBoss jboss.xml and Geronimo openejb-jar.xml as they were already provided by the sample application. These files are located in the <session_home>/dd/META-INF directory. The following example shows the JBoss deployment descriptor. jboss.xml <?xml version="1.0"?> <jboss> <container-configurations> <container-configuration> <container-name>Standard BMP EntityBean</container-name> <commit-option>A</commit-option> </container-configuration> </container-configurations> <enterprise-beans> <entity> <ejb-name>CustomerEJB</ejb-name> <jndi-name>CustomerHomeRemote</jndi-name> <resource-ref> <res-ref-name>jdbc/ibm-demo</res-ref-name> <jndi-name>java:/DefaultDS</jndi-name> </resource-ref> <configuration-name>Standard BMP EntityBean</configuration-name> </entity> <session> <ejb-name>LoanManagerEJB</ejb-name> <jndi-name>LoanManagerHomeRemote</jndi-name> <ejb-ref> <ejb-ref-name>ejb/CustomerHomeRemote</ejb-ref-name> <jndi-name>CustomerHomeRemote</jndi-name> </ejb-ref> </session> <session> <ejb-name>StatefulLoanManagerEJB</ejb-name> <jndi-name>StatefulLoanManagerHomeRemote</jndi-name> <ejb-ref> <ejb-ref-name>ejb/CustomerHomeRemote</ejb-ref-name> <jndi-name>CustomerHomeRemote</jndi-name> </ejb-ref> </session> </enterprise-beans> </jboss> Compare it with the contents of the Geronimo deployment plan shown in the following example. openejb-jar.xml <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="SessionBeanDemo" parentId="org/apache/geronimo/Server"> <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 org/apache/geronimo/Server, then follows the definition of the EJBs. The entity element defines an entity bean. The resource-ref element defines the data source that this EJB will be using. Then the session beans are defined in the session element as well as their jndi references in the ejb-ref elements. Here is a detailed listing of the elements:
Set the JNDI propertiesEdit the jndi.properties file located in in the <session_home>/jndi directory as shown in the following example: jndi.properties #################################################################### ### JBoss Settings #################################################################### #java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory #java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces #java.naming.provider.url=localhost #################################################################### ### Geronimo Settings #################################################################### java.naming.factory.initial=org.openejb.client.RemoteInitialContextFactory java.naming.provider.url=localhost:4201 java.naming.security.principal=username java.naming.security.credentials=passwd Modify the WAR filesOpen the web.xml file located in the <session_home>/src/webapp/WEB-INF directory and comment out the following taglib element: Excerpt from the web.xml file ... <!-- <taglib> <taglib-uri>http://java.sun.com/jstl/core</taglib-uri> <taglib-location>/WEB-INF/tld/c.tld</taglib-location> </taglib> --> ... Open the two jsp files, stateless.jsp and stateful.jsp located in the <session_home>/src/webapp directory and make sure you replace the following line: <%@ taglib prefix="c" uri="http://java.sun.com/jstl/core" %> - this is used for JBoss. with this other: <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> - this is used for Apache Geronimo. Build the sample applicationBuild the migrated Session Bean sample application by running the following command from the <session_home> directory: maven ejb war This command will create the session-ejb-SNAPSHOT.jar and session-ejb.war files in the <session_home>/target directory. Deploy the migrated applicationIn order to deploy the application make sure the Geronimo server is up and running. From a command line change directory to <session_home> and type the following command: maven geronimo:deploy Once the application is deployed and started you can verify its status by typing the following command from the <geronimo_home>/bin directory: java -jar deployer.jar --user system --password manager list-modules Look for the SessionBeanDemo and SessionWebApp entries. To test the migrated Session Bean application run the following commands from the <session_home> directory: maven run-g:stateless - for the stateless client The following example shows the results of the stateless session client.
The following example shows the results of the stateful session client.
If you run the stateless client again you will see now some customers with a denied loan application.
As with JBoss, you can also run the Web Application client by pointing a Web browser to the following URL: 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. SummaryThis article has shown how to migrate a sample application that uses Session Beans, from JBoss v4.0.2 to Apache Geronimo. This article provided step-by-step instructions to build the application, deploy and run it, and then migrate it to the Geronimo environment. The following list summarizes the major differences found during this sample application migration.
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Document generated by Confluence on Dec 15, 2005 19:14 |