dynamic task execution in java

I'd like to hear some advice on which technologies to use to solve this problem.

I would like a task executor based on events. These tasks are created by the user (in this moment I am thinking that a task would be a java class that implements the interface task, but I'm open to suggestions). Then the user could load a "jar" or "ear" in the application and using java reflection could execute new tasks.

Another approach I can think of would be that the user creates these tasks in a ejb, deploy the ear and make the ejb loockup to run tasks.

I appreciate any advice. sorry for my english

via Chebli Mohamed