Developing message-driven beans

You can develop a bean implementation class for a message-driven bean as introduced by the Enterprise JavaBeans specification. A message-driven bean (MDB) is a message consumer that implements business logic and runs on the server.

Before you begin

Determine the messaging model you want for your application regarding use of topics, queues, producers and consumers, publish or subscribe, and so on. You can refer to the message-driven bean component contract that is described in the Enterprise JavaBeans™ specification.

About this task

A message-driven bean (MDB) is a consumer of messages from a Java Message Service (JMS) provider. An MDB is invoked on arrival of a message at the destination or endpoint that the MDB services. MDB instances are anonymous, and therefore, all instances are equivalent when not actively servicing a client message. The container controls the life cycle of bean instances, which hold no state that is visible to a client.

The following example is a basic message-driven bean:

@MessageDriven(activationConfig={
                @ActivationConfigProperty(propertyName="destination",     propertyValue="myDestination"),
                @ActivationConfigProperty(propertyName="destinationType", propertyValue="javax.jms.Queue")
})
public class MsgBean implements javax.jms.MessageListener {

  public void onMessage(javax.jms.Message msg) {

      String receivedMsg = ((TextMessage) msg).getText();
      System.out.println("Received message: " + receivedMsg);

   }

}
As with other enterprise bean types, you can also declare metadata for message-driven beans in the deployment descriptor rather than using annotations, for example:
<?xml version="1.0" encoding="UTF-8"?>

<ejb-jar id="EJBJar_1060639024453" version="3.0"
      xmlns="http://java.sun.com/xml/ns/javaee"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/ejb-jar_3_0.xsd"
      metadata-complete="false">
  <enterprise-beans>

    <message-driven>

      <ejb-name>MsgBean</ejb-name>
      <ejb-class>com.acme.ejb.MsgBean</ejb-class>
      <activation-config>
         <activation-config-property>
            <activation-config-property-name>destination</activation-config-property-name>
            <activation-config-property-value>myDestination</activation-config-property-value>
         </activation-config-property>
         <activation-config-property>
           <activation-config-property-name>destinationType</activation-config-property-name>
           <activation-config-property-value>javax.jms.Queue</activation-config-property-value>
        </activation-config-property>
      </activation-config>

    </message-driven>

  </enterprise-beans>
</ejb-jar>

Procedure

Results

You developed a simple message-driven bean, along with some deployment and packaging options.

What to do next

Read related information about designing an enterprise application that uses message-driven beans.



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Last updatedLast updated: Sep 19, 2011 7:16:32 PM CDT
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