net.dempsy.util.executor

Class RunningEventSwitch

java.lang.Object

net.dempsy.util.executor.RunningEventSwitch

public class RunningEventSwitch
extends Object

This is a helper class for coordinating a "restartable" job. A "restartable" job is one that can be started over before it's finished but there should only be on running at a time. To use it you should instantiate a RunningEventSwitch.

When you execute a job in another thread:

• the job should indicate it's started by calling workerRunning().
• When the worker completes the job it should call workerFinished().
• The worker should be checking wasPreempted() and if it ever returns 'true' the worker should exit.
• The initiating (parent) thread should wait for the worker to start by calling waitForWorkerToStart().
• If it subsequently needs to restart the job it should call preemptWorkerAndWait(), and then it can restart the job using a new Thread.

The RunningEventSwitch can also monitor an externally supplied "isRunning" flag so that the job will be 'preempted' whenever that's also set to false

Constructor Summary

Constructors

Constructor and Description
RunningEventSwitch()
RunningEventSwitch(AtomicBoolean externalIsRunning)

Method Summary

Modifier and Type	Method and Description
void	preemptWorkerAndWait() The main thread uses this method when it needs to preempt the worker and wait for the worker to finish before continuing.
void	waitForWorkerToStart() This allows the main thread to wait until the worker is started in order to continue.
boolean	wasPreempted() The worker thread can use this method to check if it's been explicitly preempted.
void	workerFinished() The worker thread should indicate that it's done in a finally clause on it's way out.
void	workerRunning() This is called from the worker thread to notify the fact that it's been started.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RunningEventSwitch

public RunningEventSwitch(AtomicBoolean externalIsRunning)

RunningEventSwitch

public RunningEventSwitch()

Method Detail

workerRunning

public void workerRunning()

This is called from the worker thread to notify the fact that it's been started.

wasPreempted

public boolean wasPreempted()

The worker thread can use this method to check if it's been explicitly preempted.

Returns:

workerFinished

public void workerFinished()

The worker thread should indicate that it's done in a finally clause on it's way out.

preemptWorkerAndWait

public void preemptWorkerAndWait()

The main thread uses this method when it needs to preempt the worker and wait for the worker to finish before continuing.

waitForWorkerToStart

public void waitForWorkerToStart()

This allows the main thread to wait until the worker is started in order to continue. This method only works once. It resets the flag so a second call will block until another thread calls to workerInitiateRun().