Universal Messaging Developer Guide : Enterprise APIs : Enterprise Developer's Guide for Java : Message Queues : Synchronous Queue Consuming
Synchronous Queue Consuming
Synchronous queue consumers consume events by calling pop() on the Universal Messaging queue reader object. Each pop call made on the queue reader will synchronously retrieve the next event from the queue.
An example of a synchronous queue reader is shown below:



public class mySyncQueueReader {


nQueueSyncReader reader = null;
nQueue myQueue = null;

public mySyncQueueReader() throws Exception {


// construct your session and queue objects here

// construct the queue reader

nQueueReaderContext ctx = new
nQueueReaderContext(this, 10);

reader = myQueue.createReader(ctx);


}

public void start() throws Exception {
while (true) {
// pop events from the queue

nConsumeEvent event = reader.pop();

go(event);
}
}

public void go(nConsumeEvent event) {
System.out.println("Consumed event "+event.getEventID());
}

public static void main(String[] args) {
try {
mySyncQueueReader sqr = new mySyncQueueReader();
sqr.start();
} catch (Exception e) {
e.printStackTrace();
}
}
}

Synchronous queue consumers can also be created using a selector, which defines a set of event properties and their values that a consumer 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.
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