What is Java Message Service (JMS) for?

Question

I am currently evaluating JMS and I don't get what I could use it for.

Currently, I believe this would be a Usecase: I want to create a SalesInvoice PDF and print it when an SalesOrder leaves the Warehouse, so during the Delivery transaction I could send a transactional print request which just begins when the SalesOrder transaction completes successfully.

Now I found out most JMS products are standalone server.

• Why would a need a Standalone Server for Message Processing, vs. e.g. some simple inproc processing with Quartz scheduler?
• How does it interact with my application?
• Isn't it much too slow?
• What are Usecases you already implemented successfully?

Answer 1

JMS is an amazingly useful system, but not for every purpose.

It's essentially a high-level framework for sending messages between nodes, with options for discovery, robustness, etc.

One useful use case is when you want a client and a server to talk to one another, but without the client actually having the server's address (E.g., you may have more than one server). The client only needs to know the broker and the queue/topic name, and the server can connect as well.

JMS also adds robustness. For instance, you can configure it so that if the server dies while the client sends messages or the other way around, you can still send messages from the client or poll messages from the server. If you ever tried implementing this directly with sockets - it's a nightmare.

The scenario you describe sounds like a classic J2EE problem, why are you not using a J2EE framework? JMS is often used inside J2EE for communications, but you got all the other benefits.

Answer 2

What ist Java Message Service (JMS) for

JMS is a messaging standard that allows Java EE applications to create, send, receive, and consume messages in a loosely coupled, reliable, and asynchronous way. I'd suggest to read the Java Message Service API Overview for more details.

Why would a need a Standalone Server for Message Processing, vs. e.g. some simple inproc processing with Quartz scheduler?

Sure, in your case, Quartz is an option. But what if the invoice system is a remote system? What if you don't want to wait for the answer? What if the remote system is down when you want to communicate with it? What if the network is not always available? This is where JMS comes in. JMS allows to send a message guaranteed to be delivered and to consume it in a transactional way (sending or consuming a message can be part of a global transaction).

How does it interact with my application?

JMS supports two communication modes: point-to-point and publish/subscribe (if this answers the question).

Isn't it much too slow?

The MOMs I've been working with were blazing fast.

What are Usecases you already implemented successfully?

Used in system such as a reservation application, a banking back-office (processing market data), or more simply to send emails.

See also

• EJB Message-Driven Beans