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 method must be declared as public.
The method must not be declared as final or static.
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:
The return type must be void.
The method must have a single argument of type javax.jms.Message.
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; logger.info("MESSAGE BEAN: Message received: " + msg.getText()); } else { logger.warning("Message of wrong type: " + inMessage.getClass().getName()); } } catch (JMSException e) { e.printStackTrace(); mdc.setRollbackOnly(); } catch (Throwable te) { te.printStackTrace(); } }