CODEWITHSUNDEEP
jmsproducer-consumer
lanoxx
lanoxx

Reputation: 13061

JMS Producer-Consumer-Observer (PCO)

In JMS there are Queues and Topics. As I understand it so far queues are best used for producer/consumer scenarios, where as topics can be used for publish/subscribe. However in my scenario I need a way to combine both approaches and create a producer-consumer-observer architecture.

Particularly I have producers which write to some queues and workers, which read from these queues and process the messages in those queues, then write it to a different queue (or topic). Whenever a worker has done a job my GUI should be notified and update its representation of the current system state. Since workers and GUI are different processes I cannot apply a simple observer pattern or notify the GUI directly.

What is the best way to realize this using a combination of queues and/or topics? The GUI should always be notified, but it should never consume anything from a queue?

I would like to solve this with JMS directly and not use any additional technology such as RMI to implement the observer part.

To give a more concrete example:

  1. I have a queue with packages (PACKAGEQUEUE), produced by machine (PackageProducer)
  2. I have a worker which takes a package from the PACKAGEQUEUE adds an address and then writes it to a MAILQUEUE (AddressWorker)
  3. Another worker processes the MAILQUEUE and sends the packages out by mail (MailWorker).
  4. After step 2. when a message is written to the MAILQUEUE, I want to notify the GUI and update the status of the package. Of course the GUI should not consume the messages in the MAILQUEUE, only the MailWorker must consume them.

Upvotes: 0

Views: 801

Answers (1)

Shashi
Shashi

Reputation: 15283

You can use a combination of queue and topic for your solution.

Your GUI application can subscribe to a topic, say MAILQUEUE_NOTIFICATION. Every time (i.e at step 2) PackageProducer writes message to MAILQUEUE, a copy of that message should be published to MAILQUEUE_NOTIFICATION topic. Since the GUI application has subscribed to the topic, it will get that publication containing information on status of the package. GUI can be updated with the contents of that publication.

HTH

Upvotes: 1

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