Why mdb java

Configure the JMS resources deployment descriptor, where you set up the connection factory and the destination. Implement the configuration XML Schema file. More information: Deploying the EAR. Create the JMS client that sends messages. More information: Running the Example.

The default is one day. If the transaction has not completed in this timeframe, the transaction is rolled back. Create a connection from the connection factory. For a queue, start the connection.

Create a session over the connection. Providing the retrieved JMS Destination , create a sender for a queue, or a publisher for a topic.

Create the message. Send out the message using either the queue sender or the topic publisher. Close the queue session. Close the connection for either JMS Destination types.

If you have another EJB acting as the MDB client, you can retrieve the connection factory and the JMS Destination using logical references that have been configured in the client-side deployment descriptor. The following defines logical names in the client-side deployment descriptor. If the client is a true Java client, this would be in its application-client. If the client is another EJB, these additions would be added in the ejb-jar.

QueueConnectionFactory or javax. Queue or javax. The following shows an example of how to define a queue and a topic. Then, you map the logical names to actual names in the OC4J deployment descriptor. If the client is a true Java client, these additions would be within the orion-application-client. If the client is another EJB, these additions are added to the orion-ejb-jar. The following example maps the logical names for the connection factories, topic and queue defined above in the client deployment descriptor to their actual JNDI names.

Once the mapping is complete, you can modify your JNDI lookup to use the logical name, as follows:. That is, the appropriate QueueReceiver or TopicSubscriber is created by the container. A message-driven bean is an enterprise bean that allows Java EE applications to process messages asynchronously. This type of bean normally acts as a JMS message listener, which is similar to an event listener but receives JMS messages instead of events. The messages can be sent by any Java EE component an application client, another enterprise bean, or a web component or by a JMS application or system that does not use Java EE technology.

Message-driven beans can process JMS messages or other kinds of messages. The most visible difference between message-driven beans and session beans is that clients do not access message-driven beans through interfaces.

Interfaces are described in the section Accessing Enterprise Beans. Unlike a session bean, a message-driven bean has only a bean class.

All instances of a message-driven bean are equivalent, allowing the EJB container to assign a message to any message-driven bean instance. The container can pool these instances to allow streams of messages to be processed concurrently. The instance variables of the message-driven bean instance can contain some state across the handling of client messages, such as a JMS API connection, an open database connection, or an object reference to an enterprise bean object.

Client components do not locate message-driven beans and invoke methods directly on them. Instead, a client accesses a message-driven bean through, for example, JMS by sending messages to the message destination for which the message-driven bean class is the MessageListener. They do not represent directly shared data in the database, but they can access and update this data.

The onMessage method can call helper methods or can invoke a session bean to process the information in the message or to store it in a database. A message can be delivered to a message-driven bean within a transaction context, so all operations within the onMessage method are part of a single transaction.

If message processing is rolled back, the message will be redelivered. Session beans allow you to send JMS messages and to receive them synchronously but not asynchronously. A message driven bean has some similarities with a stateless session bean, in the part that it is pooled too.

Well, lets tell our chat-app to listen for incoming messages. That we do by implementing MessageListener and overriding the onMessage Message message. Then this app "listens" for incoming messages, and the messages picked up are processed by onMessage Message message method.