[jboss-user] [J2EE Design Patterns] - Concurent creating problem

[johnmm1997]

I'm programming a system where people can submit "tasks" for evaluating.

When a person submit a task, the request go into a JMS queue, and later on a MDB is processing the task.

Task is an entity.
If there is no task with that id, i need to create it first (long operation)

The problem-
If there are 2 tasks request with the same id, and the id isnt in the db yet, the task is created twice (sometimes)

As a javaSE programmer, i thought about creating a singleton with concurentHashMap to flag which id's being created, but i learn that you cannot use singeltons in javaEE (mostly due to clustering scaling i guess)

so, what is the solution?

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