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
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.