Martin: Created page with "* Typically used as an asynchronous communication mechanism - loosely coupled * point to point => queue based (typically) one receiver - only one receiver receives the message..."

2021-09-14T21:23:46Z

Created page with "* Typically used as an asynchronous communication mechanism - loosely coupled * point to point => queue based (typically) one receiver - only one receiver receives the message..."

New page

* Typically used as an asynchronous communication mechanism - loosely coupled
* point to point => queue based (typically) one receiver - only one receiver receives the message
* publish subscribe => topics => multiple receivers - all receivers receive the message

* JMS application
** JMS Client - application
** JMS Provider - routing and delivery of mesages - typically one per JMS application

== Message broker ==
* routing
* transactions
* reliable delivery
Optional:
* message priority
* ordering
* message transformation

== Synchronous messaging ==
http://java.sun.com/j2ee/sdk_1.3/techdocs/api/javax/jms/QueueRequestor.html

http://blogs.sun.com/fkieviet/entry/request_reply_from_an_ejb

Which discuses issues with transactions within an EJB and needing to commit the message to the JMS queue.

= Sender =
<pre>
@Resource(mappedName="FooJMSFactory")
private ConnectionFactory cf;
@Resource(mappedName="FooTopic")
private Topic topic;

public void send() {
Connection con = cf.createConnection();
Session session = con.createSession(true, Session.AUTO_ACKNOWLEDGE); // should be ignored and handled by container
MessageProducer producer = session.createProducer(topic);
TextMessage msg = session.createTextMessage();
msg.setText("foo");
producer.send(msg);
connect.close();
}
</pre>
Types of message:
# TextMessage
# MapMessage
# ObjectMessage
# StreamMessage
# BytesMessage

= MDB =
Reference http://download.oracle.com/docs/cd/B25221_04/web.1013/b14428/mdb30cfg.htm

* Must have @MessageDriven or deployment descriptor
** mapped name element points to the queue/topic or may use ActivationConfigProperty
* class must be public - not final
* must have no arg public constructor
* must no have a finalize() method
* should implement the interface MessageListener
** or interface for specific message provider - now JCA support JMS more flexibility - typically a different type of message parameter
* ''no longer needs to implement MessageDriventBean''
** can declare the messaging-type - listener interface in the deployment descriptor

* @ActivationConfigProperty - more advanced configuration

<pre>
@MessageDriven(mappedName="jms/Topic",activationConfig=
{@ActivationConfigProperty(propertyName="connectionFactoryJndiName", propertyValue="jms/TopicConFact"),
@ActivationConfigProperty(propertyName="destinationName", propertyValue="jms/Topic"),
@ActivationConfigProperty(propertyName="destinationType", propertyValue="javax.jms.Topic"),
@ActivationConfigProperty(propertyName="messageSelector", propertyValue="Header = ’Important’"),
@ActivationConfigProperty(propertyName="acknowledgeMode", propertyValue="Auto-acknowledge"),
@ActivationConfigProperty(propertyName="subscriptionDurability", propertyValue="Durable")
})

public class XMessageBean implements MessageListener {
@Resource
private MessageDrivenContext mdc;

public void onMessage(Message m) {

// error mdc.setRollbackOnly();
</pre>

== MessageListener method ==
* must be public void
* must not be final or static
* must have only argument - Message

== MessageDrivenContext ==
Extends EJBContext adds nothing

== ActivationConfigProperty ==
=== subscriptionDurability ===
Durable = messages are kept until bean is available
NonDurable = messages are lost if bean is unavailable

== Message Linking ==
Allows routing to a specific MDB within same deployment
* deployment descriptor: message-destination-link - not supported in annotations
* can be used to define logical queues and map at deployment descriptor time
* JCA can use to route inbound messages to MDB
* container may bypass JMS provider - must still adhere to contract

== JMS & JCA ==
As of JCA 1.5 there is a standard way of plugging in a JMS provider into a Application Server.
Project to do so for 1.5 and 1.4 here: [http://java.sun.com/j2ee/connector/]

JMS - Revision history

Martin: Created page with "* Typically used as an asynchronous communication mechanism - loosely coupled * point to point => queue based (typically) one receiver - only one receiver receives the message..."