Question

I read the hornetQ documentation, confused a lot. Can someone give an exact example to create a JMS topic in hornetQ. I mean the xml configurations in hornetq-jms.xml and hornetq-configuration.xml. assume we have a topic named top and 2 subscribers named: sub1, sub2. what I get is that we should define two queues(one for each subscribers) and bind them to an address which is the topic name actually, but how the subscriber would know they should connect to which one?(They only know the topic name)

Answer 1

I think you are confused by the way HornetQ handles topics internaly in contrast to the way the JMS specification describes topics.

Let’s start with the JMS specification. Here you have one topic, where n subscribers can listen to the messages, that will be published by a client. In JMS we talk only about the destination in singular, eg. we’ll send a message to the topic, or the queue respectively.

HornetQ is a JMS Provider – a server that implements the JMS specification, so Java-clients can connect to it, and use the JMS-API. The JMS Provider might change, but the code should still work when using another JMS provider.

However, HornetQ does not distinguish internally the destinations (topic or queue), since it tries to be a generic messaging middleware. In HornetQ all topics or queues are implemented as “addresses” and “queues”. When you use the HornetQ API (CoreAPI) instead of the JMS-API, you have to deal with such things. You should read the Address section in the HornetQ documentation:

In core, there is no concept of a Topic, Topic is a JMS only term.
Instead, in core, we just deal with addresses and queues.

For example, a JMS topic would be implemented by a single address to
which many queues are bound. Each queue represents a subscription of
the topic. A JMS Queue would be implemented as a single address to
which one queue is bound – that queue represents the JMS queue.

For an example how to use a topic with JMS via HornetQ, I stongly recommend the examples that come with HornetQ itself. After donwloading and extracting the hornetq archive, just go to the examples/jms/topic directory and see the readme.html for a brief overview how to implement and how to execute the example (mvn verify).