Re: Exdecuting time consuming task in EJB
Simon wrote:
I am develpoing a Java application that enables the user to assemble
certain kinds of workflows and execute these. The execution of such a
process can take a long time (several hours).
Now, I want to transform this application to an enterprise version. The
user can assemble the workflow on its client, hand it over to the
server, and the server executes it (immediately, or at a scheduled time,
or regularly, etc.). The user can monitor the progress using a thin web
client and collect the results when the workflow finishes.
Clearly, these processes must be executed asynchronously and
concurrently. It would also be good to have control over the scheduler
so the user can inspect and potentially modify the queue. Furthermore,
workflows, as they are currently implemented, spawn threads to execute
subtasks in parallel (using an Executor).
It appears to me that executing and scheduling can be performed using a
EJB Timer (possibly with zero delay), although I must give up control
over ther scheduler. However, spawning threads from an EJB seems to be
evil, if I understand the documentation correctly.
It is not just evil - it is strictly forbidden.
I am not sure that
this would do any harm in my case since the individual workflows do not
interact with each other, and, while they are running, not even with a
database, but I am relatively new to Java EE.
The app server manages threads based on an assumption that components
plays by the rule.
My questions are these:
- Is a Java EE the right environment for my problem?
- Is there an enterprise server that has good support for concurrency
and long-running tasks?
I think you should look as message queues, JMS and message driven beans.
Arne