This repository includes examples of JMS message producers and consumers for JMS queues as well as topics.
For more information check this reference
To check JMS connection information, read the comments in the code. You need to configure and add wlthin3client.jar file into this project.
For GlassFish project examples, get gf-client.jar file.
There are different types of messages we can send.
- TextMessage
- MapMessage (key value pairs)
- ObjectMessage (can be any Java serializable object)
- Bytes Message (array of bytes as payload)
- StreamMessage (Strings and primitives)
We can set delivery mode, priorities and time to live for messages. There are 10 levels of priority ranging from 0 to 9. 0 is the minimum priority. JMS tries to deliver higher-priority messages first but this is not guaranteed. Message Expiration time is called "TimeToLive" which is set in milliseconds. The default value is 0 which means it expires in 0 seconds.
We can enable transactions on JMS by enabling it in createSession method.
By setting createSession(true,...), we can have enabled transaction. If we enable, we must call session.commit() to put the messages to the queue. Usually, the messages will be put one by one and usually transaction will be disabled for the producers.
The second argument in this method has little meaning for the senders, but we need it because Java works on interfaces and there is no single argument version for this method.
On the receiver side, Session.AUTO_ACKNOWLEDGE means JMS will auto acknowledge if Listener succeeded without exception.
We can set CLIENT_ACKNOWLEDGE to acknowledge method. However, this method works only with consumer.receive() method and not with listener interface.
In JMS, the message sender and message receiver are separate entities and there may be hours of lag between the two processes. When onMessage() method throws exception, the server transfers the message to Dead Message Queue (DMQ). If the messages is of unexpected type, those messages are called poisonous messages and are also routed to DMQ.
If an exception is thrown from a receiver code, we can ask JMS provider to redeliver for specific number of times or after delaying for specific amount of time.