2007-10-15

JCA classloading

First off. No blog sightings from my friend, it is a sad state of affairs.

Now, for something that definately does not zoom. JCA classloading. Have you read the specification yet? Many, many pages about the contract between the resource adapter and its environment. All fine and dandy. Very complex I'll grant you but still, it is described.
Then you read up on the packaging, the usual java stuff, zip files and place a magic file to configure it. So you create the RAR-file. Then you write a client. But wait! The client and the adapter shares an interface. In what archive does that go?
And that, as they say, is the question.

If you have a webapp it has its own classloader, the JCA has another. So they do not see each other. Which is mostly ok until you come to the shared code. You have to place it in a classloader that both see. Which one is that then? Place it on the classpath of the entire application server? That works of course but kind of defeats the entire point of having deployable archives lite WAR & RAR.
The only working alternative I've found is to place both the client and the resource adapter in an EAR and then totally mess about with the classloading mechanism in the application server. Both weblogic and JBoss can be coerced into some kind of hierarchy that works. But still. Why oh why couldn't the JEE specification have decided how to do this?
Now we're stuck with application server specific black magic to get the damned thing to work.
JCA does not zoom.

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