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Asynchronous
queue consumers consume events from a callback on an
interface that all asynchronous consuemrs must implement.
We call this interface an nEventListener. The
listener interface defines one method called 'go'
which when called will pass events to the consumer
as they are delivered from the Nirvana Realm Server.
An example of an asynchronous queue reader is shown
below:
public class myAsyncQueueReader implements nEventListener
{
nQueue myQueue = null;
public myAsyncQueueReader() throws Exception
{
// construct
your session
and queue objects
here
// begin consuming
events from the queue
nQueueReaderContext ctx = new
nQueueReaderContext(this, 10);
nQueueAsyncReader reader = myQueue.createAsyncReader(ctx);
}
public void go(nConsumeEvent event) {
System.out.println("Consumed event "+event.getEventID());
}
public static void main(String[] args) {
try {
new myAsyncQueueReader();
} catch (Exception e) {
e.printStackTrace();
}
}
}
Asychronous queue consumers can also be created using
a selector, which defines a set of event
properties and their values that a subscriber is
interested in. For example if events are being published
with the following event properties:
nEventProperteis props =new nEventProperties();
props.put(“BONDNAME”,”bond1”);
If you then provide a message selector string in the
form of:
String selector = "BONDNAME='bond1'";
And pass this string into the constructor for the nQueueReaderContext
object shown in the example code, then your consumer
will only consume messages that contain the correct
value for the event property BONDNAME.
An example of an asynchronous queue reader can be found
here.
For more information on Nirvana message queues, please
see the API documentation.
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