The Message-Driven Bean Class

The code for the SimpleMessageBean class illustrates the requirements of a message-driven bean class:

Unlike session beans and entities, message-driven beans do not have the remote or local interfaces that define client access. Client components do not locate message-driven beans and invoke methods on them. Although message-driven beans do not have business methods, they may contain helper methods that are invoked internally by the onMessage method.

The MessageDriven annotation typically contains a mappedName element that specifies the JNDI name of the destination from which the bean will consume messages. For complex message-driven beans there can also be an activationconfig element containing ActivationConfigProperty annotations used by the bean. See A Java EE Application That Uses the JMS API with a Session Bean (page 1062) for an example.

A message-driven bean can also inject a MessageDrivenContext resource. Commonly you use this resource to call the setRollbackOnly method to handle exceptions for a bean that uses container-managed transactions.

Therefore, the first few lines of the SimpleMessageBean class look like this:

public class SimpleMessageBean implements MessageListener { 
  private MessageDrivenContext mdc;

The onMessage Method

When the queue receives a message, the EJB container invokes the message listener method or methods. For a bean that uses JMS, this is the onMessage method of the MessageListener interface.

A message listener method must follow these rules:

The onMessage method is called by the bean's container when a message has arrived for the bean to service. This method contains the business logic that handles the processing of the message. It is the message-driven bean's responsibility to parse the message and perform the necessary business logic.

The onMessage method has a single argument: the incoming message.

The signature of the onMessage method must follow these rules:

In the SimpleMessageBean class, the onMessage method casts the incoming message to a TextMessage and displays the text:

public void onMessage(Message inMessage) {
  TextMessage msg = null;

  try {
    if (inMessage instanceof TextMessage) {
      msg = (TextMessage) inMessage;"MESSAGE BEAN: Message received: " +
    } else {
      logger.warning("Message of wrong type: " +
  } catch (JMSException e) {
  } catch (Throwable te) {