Re: QueueBrowser and unacked received messages

Anders Bogdan wrote:
> Greetings!
> I was wondering if someone could explain or suggest a solution to the  
> behavior I'm seeing?
>
> using openjms-0.7.6.1, and a queue.
> I'm trying to avoid having functionally equivalent jms messages on  
> the queue at the same time.
>
> I thought I could determine this by using a QueueBrowser and a  
> message selector but apparently queued messages that are received but  
> not ack'd (and take quite awhile to process) are skipped by the  
> selector - at least they aren't returned in the browsers enumeration.
>
> Is there a way to detect messages in this condition?
> In my scenario the jms messages represent a request for a service and  
> it doesn't make sense to have multiple copies of the same request on  
> the queue at the same time.
>
> Thanks.
>   
Once a message has been delivered, it is not available to QueueBrowsers, 
unless
they had that message cached locally.
You could use a second queue that the processor could use to indicate 
that it is processing a request.
This would be consumed by the processor once the processing is complete.
The sender would check this second queue before issuing requests.

However, it sounds like you need a different approach. Have you looked 
at QueueRequestor?
http://java.sun.com/j2ee/sdk_1.3/techdocs/api/javax/jms/QueueRequestor.html

-Tim



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