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public interface ManagedTaskListener
A ManagedTaskListener is used to monitor the state of a task's Future.
It can be registered with a ManagedExecutorService
using the
submit
methods and will be invoked when the state of the Future changes.
Each listener method will run with the same context in which the task runs.
The listener becomes a Contextual Task. All listeners run without an explicit transaction (they do not enlist in the application
component's transaction). If a transaction is required, use a
UserTransaction
instance.
Each listener instance will be invoked within the same process in which the listener was registered. If a single listener is submitted to multiple ManagedExecutorService instances, the listener object may be invoked concurrently by multiple threads.
Each listener method supports a minimum quality of service of at-most-once. A listener is not guaranteed to be invoked due to a process failure or termination. State Transition Diagram The following state transition figure and tables describe the possible task lifecycle events that can occur when a ManagedTaskListener is associated with a task. Each method is invoked when the state of the future moves from one state to another.
A. The task runs normally:
Sequence | State | Action | Listener | Next state |
1. | None | submit() | taskSubmitted | Submitted |
2. | Submitted | About to call run() | taskStarting | Started |
3. | Started | Exit run() | taskDone | Done |
B. The task is cancelled during taskSubmitted():
Sequence | State | Action | Listener | Next state |
1. | None | submit() | taskSubmitted Future is cancelled. | Cancelling |
2. | Cancelling | taskAborted | Cancelled | |
3. | Cancelled | taskDone | Done |
C. The task is cancelled or aborted after submitted, but before started:
Sequence | State | Action | Listener | Next state |
1. | None | submit() | taskSubmitted | Submitted |
2. | Submitted | cancel() or abort | taskAborted | Cancelled |
3. | Cancelled | taskDone | Done |
D. The task is cancelled when it is starting:
Sequence | State | Action | Listener | Next state |
1. | None | submit() | taskSubmitted | Submitted |
2. | Submitted | About to call run() | taskStarting Future is cancelled. | Cancelling |
3. | Cancelling | taskAborted | Cancelled | |
4. | Cancelled | taskDone | Done |
Method Summary | |
---|---|
void |
taskAborted(Future<?> future,
ManagedExecutorService executor,
Throwable exception)
Called when a task�s Future has been cancelled anytime during the life of a task. |
void |
taskDone(Future<?> future,
ManagedExecutorService executor,
Throwable exception)
Called when a submitted task has completed running, successful or otherwise after submitted. |
void |
taskStarting(Future<?> future,
ManagedExecutorService executor)
Called when a task is about to start running. |
void |
taskSubmitted(Future<?> future,
ManagedExecutorService executor)
Called after the task has been submitted to the Executor. |
Method Detail |
---|
void taskSubmitted(Future<?> future, ManagedExecutorService executor)
This event does not indicate that the task has been scheduled for execution.
future
- the future instance that was created when the task was submitted.
The Future.get()
methods should not be used within the scope
of this listener method, as they may cause deadlocks.executor
- the executor used to run the associated Future.void taskAborted(Future<?> future, ManagedExecutorService executor, Throwable exception)
Future.isCancelled()
method returns false if the task was aborted
through another means other than Future.cancel(). The Future.get() method will throw
an exception that will represent the cause of the cancellation:
CancellationException
if the task was cancelled,
SkippedException
if the task was skipped or
AbortedException
if the task failed to start for another reason.
AbortedException#getCause()
method will return the exception
that caused the task to fail to start.
future
- the future instance that was created when the task was submitted.executor
- the executor used to run the associated Future.void taskDone(Future<?> future, ManagedExecutorService executor, Throwable exception)
future
- the future instance that was created when the task was submitted.executor
- the executor used to run the associated Future.void taskStarting(Future<?> future, ManagedExecutorService executor)
This method may be called from the same thread that the task was submitted with.
future
- the future instance that was created when the task was submitted.
The Future.get()
methods should not be used within the scope
of this listener method, as they may cause deadlocks.executor
- the executor used to run the associated Future.
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