exact example for JMS Topic in HornetQ

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

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).