Lightweight Message Bus library

Question

I will be starting a small Java (GWT really) project in the near future and I am at "information gathering" phase.

Q: Is there a lightweight Message Bus library written in Java?

My requirements are lightweight too :-)

1. async (no need for sync)
2. multicast and point-to-point
3. no strict message ordering
4. message "envelope" ideally "owned" by Message Bus (i.e. in terms of life-cycle management)
5. localized delivery (i.e. not inter-process nor inter-node)

Update: It seems that GWT now supports an integrated "event bus".

Answer 1

Have a look at eventbus.

Answer 2

Not sure if it is really lightweight. But it does fit the rest of your description: ActiveMQ

Answer 3

Maybe you could try some jabber (XMPP) based solution. What about openfire?

Answer 4

If you happen to be using Spring already, then a handy sort-of-hidden feature of Spring is the ApplicationEventMulticaster interface, which is a very simple API for publishing and subscribing to application-generated events. The implementations use the TaskExecutor framework, which means they can be sync or async as desired. Furthermore, every ApplicationContext has a publishEvent method, so it's comically easy to set it up for Spring-managed classes.

So yes, if you already use Spring, there's no need to for another utility to do this, it's built in already.