I know the topic has been discussed frequently in this forum but I can't find
the answer I'm looking for.
My question is: How to handle the concurrent access to a task assigned to an
actor pool?
findPoolTaskInstance(actorId) will return all the tasks assigned to any pool
the actor is a member of. But as long as you don't use setActorId() the task is
not assigned. Concurrent access to the same task instance (taken from the list
return by findPoolTaskInstance) will result in an exception when the data gets
persisted in the DB for processes which did not set their actorId succesfully.
| protected boolean acquire() {
| // Now acquire the very first task
| createSession();
|
| try {
| jbpmContext.setActorId(actorName);
|
| // Now we search for all the tasks waiting for our actor
| List tasksActor =
taskMgmtSession.findPooledTaskInstances(actorName);
|
| if (tasksActor.size() > 0) {
| TaskInstance task = (TaskInstance) tasksActor.get(0);
| task.setActorId(actorName);
|
| jbpmContext.save(task);
| }
| }
| catch(Exception e) {
| e.printStackTrace();
| }
| finally {
| // Tear down the pojo persistence context.
| try {
| closeSession();
| }
| catch(Exception e) {
| // If the Task is already taken you'll end up here
| e.printStackTrace();
|
| return false;
| }
| }
|
| return true;
| }
|
I'm not considering multi-threaded scenario, using synchronize would be a
solution then. Catching the exception, like illustrated above, does not look
like an elegant solution to me. Is there a better way?
Best regards,
Johan
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