An message-driven bean is an enterprise bean that is an
asynchronous, JMS message consumer. It is similar to a stateless
session bean but lacks a home or remote interface. It can reliably
consume messages from a queue or a durable subscription. The
messages may be sent by any J2EE component--from an application
client, another EJB, or a Web component. It contains an
onMessage method that is called automatically when a message
arrives and that implements the bean's business logic.