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A Java EE Application That Uses the JMS API with a Session Bean

This section explains how to write, compile, package, deploy, and run a JavaEE application that uses the JMS API in conjunction with a session bean.The application contains the following components:

An application client that invokes a session bean
A session bean that publishes several messages to a topic
A message-driven bean that receives and processes the messages using a durable topic subscriber and a message selector

The section covers the following topics:

You will find the source files for this section in the directorytut-install/javaeetutorial5/examples/jms/clientsessionmdb/. Path names in this section are relative to this directory.

Writing the Application Components for the`clientsessionmdb` Example

This application demonstrates how to send messages from an enterprise bean (in thiscase, a session bean) rather than from an application client, as in theexample inChapter 23, A Message-Driven Bean Example.Figure 32-1 illustrates the structure of this application.

Figure 32-1 A Java EE Application: Client to Session Bean to Message-Driven Bean

Diagram of application showing an application client calling a session bean, which publishes a message that is consumed by a message-driven bean

The Publisher enterprise bean in this example is the enterprise-application equivalent of awire-service news feed that categorizes news events into six news categories. The message-drivenbean could represent a newsroom, where the sports desk, for example, would setup a subscription for all news events pertaining to sports.

The application client in the example injects the Publisher enterprise bean’s remote homeinterface and then calls the bean’s business method. The enterprise bean creates 18text messages. For each message, it sets aString property randomly to oneof six values representing the news categories and then publishes the message toa topic. The message-driven bean uses a message selector for the property tolimit which of the published messages it receives.

Writing the components of the application involves the following:

Coding the Application Client:`MyAppClient.java`

The application client program,clientsessionmdb-app-client/src/java/MyAppClient.java, performs no JMS API operations and sois simpler than the client program inChapter 23, A Message-Driven Bean Example. The program uses dependency injectionto obtain the Publisher enterprise bean’s business interface:

@EJB(name="PublisherRemote")static private PublisherRemote publisher;

The program then calls the bean’s business method twice.

Coding the Publisher Session Bean

The Publisher bean is a stateless session bean that has one business method.The Publisher bean uses a remote interface rather than a local interface becauseit is accessed from the application client.

The remote interface,clientsessionmdb-ejb/src/java/sb/PublisherRemote.java, declares a single business method,publishNews.

The bean class,clientsessionmdb-ejb/src/java/sb/PublisherBean.java, implements thepublishNews method and its helper methodchooseType.The bean class also injectsSessionContext,ConnectionFactory, andTopic resources and implements@PostConstruct and@PreDestroy callback methods. The bean class begins as follows:

@Stateless@Remote({PublisherRemote.class})public class PublisherBean implements PublisherRemote {    @Resource    private SessionContext sc;    @Resource(mappedName="jms/ConnectionFactory")    private ConnectionFactory connectionFactory;    @Resource(mappedName="jms/Topic")    private Topic topic;    ...

The@PostConstruct callback method of the bean class,makeConnection, creates theConnection usedby the bean. The business methodpublishNews creates aSession and aMessageProducer and publishes the messages.

The@PreDestroy callback method,endConnection, deallocates the resources that were allocated by the@PostConstruct callback method. In this case, the method closes theConnection.

Coding the Message-Driven Bean:`MessageBean.java`

The message-driven bean class,clientsessionmdb-ejb/src/java/mdb/MessageBean.java, is almost identical to the one inChapter 23, A Message-Driven Bean Example. However, the@MessageDriven annotation is different, because instead of a queue thebean is using a topic with a durable subscription, and it is alsousing a message selector. Therefore, the annotation sets the activation config propertiesmessageSelector,subscriptionDurability,clientId, andsubscriptionName, as follows:

@MessageDriven(mappedName="jms/Topic",activationConfig={ @ActivationConfigProperty(propertyName="messageSelector",    propertyValue="NewsType = ’Sports’ OR NewsType = ’Opinion’"),  @ActivationConfigProperty(    propertyName="subscriptionDurability",    propertyValue="Durable"),  @ActivationConfigProperty(propertyName="clientId",    propertyValue="MyID"),  @ActivationConfigProperty(propertyName="subscriptionName",    propertyValue="MySub") })

The JMS resource adapter uses these properties to create a connection factory forthe message-driven bean that allows the bean to use a durable subscriber.

Creating Resources for the`clientsessionmdb` Example

This example uses the topic namedjms/Topic and the connection factoryjms/ConnectionFactory, whichyou created inCreating JMS Administered Objects for the Synchronous Receive Example. If you deleted the connection factory or topic, you cancreate them again using targets in thebuild.xml file for this example. Usethe following commands to create the resources:

ant create-cf ant create-topic

Building, Deploying, and Running the`clientsessionmdb` Example Using NetBeans IDE

To build, deploy, and run the application using NetBeans IDE, do the following:

Start the Application Server, if it is not already running.
In NetBeans IDE, choose Open Project from the File menu.
In the Open Project dialog, navigate totut-install/javaeetutorial5/examples/jms/.
Select theclientsessionmdb folder.
Select the Open as Main Project check box and the Open Required Projects check box.
Click Open Project.
Right-click theclientsessionmdb project and choose Build.
This task creates the following:
- An application client JAR file that contains the client class file and the session bean’s remote interface, along with a manifest file that specifies the main class
- An EJB JAR file that contains both the session bean and the message-driven bean
- An application EAR file that contains the two JAR files
Right-click the project and choose Undeploy and Deploy.
Right-click the project and choose Run.
This command returns a JAR file namedclientsessionmdbClient.jar and then executes it.

The output of the application client in the Output pane looks likethis:

To view the bean output, check <install_dir>/domains/domain1/logs/server.log.

The output from the enterprise beans appears in the server log (domain-dir/logs/server.log),wrapped in logging information. The Publisher session bean sends two sets of 18messages numbered 0 through 17. Because of the message selector, the message-driven beanreceives only the messages whoseNewsType property isSports orOpinion.

Undeploy the application after you finish running the client. To undeploy the application,follow these steps:

Click the Services tab.
Expand the Servers node.
Expand the Application Server node.
Expand the Applications node.
Expand the Enterprise Applications node.
Right-clickclientsessionmdb and choose Undeploy.

To remove the generated files, right-click theclientsessionmdb project and choose Clean.

Building, Deploying, and Running the`clientsessionmdb` Example Using Ant

To build the application using Ant, do the following:

Start the Application Server, if it is not already running.

Go to the following directory:

tut-install/javaeetutorial5/examples/jms/clientsessionmdb/

To compile the source files and package the application, use the following command:
```
ant
```

Theant command creates the following:

An application client JAR file that contains the client class file and the session bean’s remote interface, along with a manifest file that specifies the main class
An EJB JAR file that contains both the session bean and the message-driven bean
An application EAR file that contains the two JAR files

Theclientsessionmdb.ear file is created in theclientsessionmdb/dist directory.

To deploy the application and run the client, use the following command:

ant run

Ignore the message that states that the application is deployed at a URL.

The client displays these lines:

running application client container.To view the bean output, check <install_dir>/domains/domain1/logs/server.log.

Undeploy the application after you finish running the client. Use the following command:

ant undeploy

To remove the generated files, use the following command in theclientsessionmdb,clientsessionmdb-app-client, andclientsessionmdb-ejb directories:

ant clean

Movatterモバイル変換

The Java EE 5 Tutorial

A Java EE Application That Uses the JMS API with a Session Bean

Writing the Application Components for theclientsessionmdb Example

Coding the Application Client:MyAppClient.java

Coding the Publisher Session Bean

Coding the Message-Driven Bean:MessageBean.java

Creating Resources for theclientsessionmdb Example

Building, Deploying, and Running theclientsessionmdb Example Using NetBeans IDE