Message brokers are essential components of eBusiness systems and enterprise solutions.
They keep delivering when everything else breaks and that point alone makes them a pilar of any enterpise IT.

From a geeky point of view they are pretty good too as they constitute a form of ultimate-IT, where there is no user involved at all. This is the only frustrating thing with such systems, no-one knows they are at work, so it is hard to brag about your fantastic achievements :-) !

Nevermind, your boss knows! That is the only thing that matters.

If you are new to Message Brokers, picture them as people-less email and chat servers.
Because there is no people, there are no mailboxes but message queues instead.
Because there is no people, there are no chats but topics instead.

In any situation where two processes need exchanging data on an Peer-to-Peer basis,
a message broker will allow that exchange by decoupling technologies and time.
This is important in eBusiness, where partners' technologies and business practives usually differ in ways no-one thought possible.

So, a message broker is a fairly adaptable piece of technology and it is rather hard to master.
Fortunately, as java shares most of brokers' ambitions, java defines the Java Message Service or JMS.

JMS lets you control and drive message brokers and most enterprise message brokers support it.
Here you go! This is how you explain the importance and success of IBM Websphere MQ, Progress Sonic MQ and Apache Active MQ...

There is still a catch!
Even with JMS, the story of a programmer's coming to Message Broking is a long one and they are neither easy to find nor easy to train. It also takes a sort of "nononsenseness" to be successful at it, the trick is to stick to absolute technique and not blend any functionality in the design. In other words, this is architect-do.