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47

answers:

1

I'm attempting to wire a queue to the front of a MessageChannel, and I need to do so programatically so it can be done at run time in response to an osgi:listener being triggered. So far I've got:

public void addService(MessageChannel mc, Map<String,Object> properties)
{
    //Create the queue and the QueueChannel
    BlockingQueue<Message<?>> q = new LinkedBlockingQueue<Message<?>>();
    QueueChannel qc = new QueueChannel(q);

    //Create the Bridge and set the output to the input parameter channel
    BridgeHandler b = new BridgeHandler();
    b.setOutputChannel(mc);

    //Presumably, I need something here to poll the QueueChannel
    //and drop it onto the bridge.  This is where I get lost

}

Looking through the various relevant classes, I came up with:

    PollerMetadata pm = new PollerMetadata();
    pm.setTrigger(new IntervalTrigger(10));

    PollingConsumer pc = new PollingConsumer(qc, b);

but I'm not able to put it all together. What am I missing?

A: 

So, the solution that ended up working for me was:

public void addEngineService(MessageChannel mc, Map<String,Object> properties)
{
    //Create the queue and the QueueChannel
    BlockingQueue<Message<?>> q = new LinkedBlockingQueue<Message<?>>();
    QueueChannel qc = new QueueChannel(q);

    //Create the Bridge and set the output to the input parameter channel 
    BridgeHandler b = new BridgeHandler();
    b.setOutputChannel(mc);

    //Setup a Polling Consumer to poll the queue channel and 
    //retrieve 1 thing at a time
    PollingConsumer pc = new PollingConsumer(qc, b);
    pc.setMaxMessagesPerPoll(1);

    //Now use an interval trigger to poll every 10 ms and attach it
    IntervalTrigger trig = new IntervalTrigger(10, TimeUnit.MILLISECONDS);
    trig.setInitialDelay(0);
    trig.setFixedRate(true);
    pc.setTrigger(trig);

    //Now set a task scheduler and start it
    pc.setTaskScheduler(taskSched);
    pc.setAutoStartup(true);
    pc.start();
}

I'm not terribly clear if all the above is explicitly needed, but neither the trigger or the task scheduler alone worked, I did appear to need both. I should also note the taskSched used was the default taskScheduler dependency injected from spring via

<property name="taskSched" ref="taskScheduler"/>
Dusty