How to publish events to a Nirvana Queue

There are 2 types of publish available in Nirvana for queues:

Reliable Publish

Transactional Publish

Reliable publish is simply a one way push to the Nirvana Server. This means that the server does not send a response to the client to indicate whether the event was successfully received by the server from the publish call.

Transactional publish involves creating a transaction object to which events are published, and then committing the transaction. The server responds to the transaction commit call indicating if it was successful. There are also means for transactions to be checked for status after application crashes or disconnects.

Reliable Publish

Once we have established our session and our queue, we then need to construct our event and publish the event onto the queue.

For reliable publish, here is the example code for how to publish events to a queue. Further examples can be found in the API documentation.

// Publishing a simple byte array message
myQueue.push(new nConsumeEvent("TAG", message.getBytes()));

// publishiing an XML document
InputStream is = new FileInputStream( aFile );
DOMParser p = new DOMParser();
p.parse( new InputSource( is ) );
Document doc = p.getDocument();
myQueue.push( "XML", doc );

Transactional Publish

Transactional publishing provides us with a method of verifying that the server receives the events from the publisher, and provides guaranteed delivery.

There are similar prototypes available to the developer for transaction publishing. Once we have established our session and our queue, we then need to construct our events and our transaction and publish these events to the transaction. Then the transaction will be committed and the events available to consumers to the queue.

Below is a code snippet of how transactional publishing is achieved:

Vector messages=new Vector();
Messages.addElement(message1);
nTransactionAttributes tattrib=new nTransasctionAttributes(myQueue);
nTransaction myTransaction=nTransactionFactory.create(tattrib);
myTransaction.publish(messages);
myTransaction.commit();

If during the transaction commit your Nirvana session becomes disconnected, and the commmit call throws an exception, the state of the transaction may be unclear. To verify that a transaction has been committed or aborted, an call can be made on the transaction that will determine if the events within the transactional were successfully received by the Nirvana Realm Server.

boolean committed = myTransaction.isCommitted(true);

Which will query the Nirvana Realm Server to see if the transaction was committed.

An example of publishing events onto a queue can be found here. An example of how to transactionally publish events to a queue can be found here. For more information on Nirvana message queues, please see the API documentation.