com.bea.wlevs.ede.impl
Class ScopedExecutor

java.lang.Object
  |
  +--java.util.concurrent.AbstractExecutorService
        |
        +--com.bea.wlevs.ede.impl.ScopedExecutor

public class ScopedExecutor
extends AbstractExecutorService
implements BlockingQueueExecutor

Work copied from Doug Lea's ThreadPoolExecutor


Inner Class Summary
static class ScopedExecutor.AbortPolicy
          A handler for rejected tasks that throws a RejectedExecutionException.
static class ScopedExecutor.CallerRunsPolicy
          A handler for rejected tasks that runs the rejected task directly in the calling thread of the execute method, unless the executor has been shut down, in which case the task is discarded.
static class ScopedExecutor.DiscardOldestPolicy
          A handler for rejected tasks that discards the oldest unhandled request and then retries execute, unless the executor is shut down, in which case the task is discarded.
static class ScopedExecutor.DiscardPolicy
          A handler for rejected tasks that silently discards the rejected task.
 
Constructor Summary
ScopedExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue workQueue, WorkFactory workFactory, WorkManager workManager, RejectedExecutionHandler handler)
           
 
Method Summary
protected  void afterExecute(Runnable r, Throwable t)
          Method invoked upon completion of execution of the given Runnable.
 boolean awaitTermination(long timeout, TimeUnit unit)
           
protected  void beforeExecute(Work w, Runnable r)
          Method invoked prior to executing the given Runnable in the given thread.
 void execute(Runnable command)
          Executes the given task sometime in the future.
protected  void finalize()
          Invokes shutdown when this executor is no longer referenced.
 int getActiveCount()
          Returns the approximate number of threads that are actively executing tasks.
 long getCompletedTaskCount()
          Returns the approximate total number of tasks that have completed execution.
 int getCorePoolSize()
          Returns the core number of threads.
 long getKeepAliveTime(TimeUnit unit)
          Returns the thread keep-alive time, which is the amount of time which threads in excess of the core pool size may remain idle before being terminated.
 int getLargestPoolSize()
          Returns the largest number of threads that have ever simultaneously been in the pool.
 int getMaximumPoolSize()
          Returns the maximum allowed number of threads.
 int getPoolSize()
          Returns the current number of threads in the pool.
 BlockingQueue getQueue()
          Returns the task queue used by this executor.
 RejectedExecutionHandler getRejectedExecutionHandler()
          Returns the current handler for unexecutable tasks.
 long getTaskCount()
          Returns the approximate total number of tasks that have been scheduled for execution.
 WorkFactory getWorkFactory()
          Returns the thread factory used to create new threads.
 boolean isShutdown()
           
 boolean isTerminated()
           
 boolean isTerminating()
          Returns true if this executor is in the process of terminating after shutdown or shutdownNow but has not completely terminated.
 int prestartAllCoreThreads()
          Starts all core threads, causing them to idly wait for work.
 boolean prestartCoreThread()
          Starts a core thread, causing it to idly wait for work.
 void purge()
          Tries to remove from the work queue all Future tasks that have been cancelled.
 boolean remove(Runnable task)
          Removes this task from the executor's internal queue if it is present, thus causing it not to be run if it has not already started.
 void setCorePoolSize(int corePoolSize)
          Sets the core number of threads.
 void setKeepAliveTime(long time, TimeUnit unit)
          Sets the time limit for which threads may remain idle before being terminated.
 void setMaximumPoolSize(int maximumPoolSize)
          Sets the maximum allowed number of threads.
 void setRejectedExecutionHandler(RejectedExecutionHandler handler)
          Sets a new handler for unexecutable tasks.
 void setWorkFactory(WorkFactory workFactory)
          Sets the thread factory used to create new threads.
 void setWorkManager(WorkManager workManager)
           
 void shutdown()
          Initiates an orderly shutdown in which previously submitted tasks are executed, but no new tasks will be accepted.
 List shutdownNow()
          Attempts to stop all actively executing tasks, halts the processing of waiting tasks, and returns a list of the tasks that were awaiting execution.
protected  void terminated()
          Method invoked when the Executor has terminated.
 
Methods inherited from class java.util.concurrent.AbstractExecutorService
invokeAll, invokeAll, invokeAny, invokeAny, submit, submit, submit
 
Methods inherited from class java.lang.Object
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

ScopedExecutor

public ScopedExecutor(int corePoolSize,
                      int maximumPoolSize,
                      long keepAliveTime,
                      TimeUnit unit,
                      BlockingQueue workQueue,
                      WorkFactory workFactory,
                      WorkManager workManager,
                      RejectedExecutionHandler handler)
Method Detail

execute

public void execute(Runnable command)
Executes the given task sometime in the future. The task may execute in a new thread or in an existing pooled thread. If the task cannot be submitted for execution, either because this executor has been shutdown or because its capacity has been reached, the task is handled by the current RejectedExecutionHandler.

Parameters:
command - the task to execute
Throws:
RejectedExecutionException - at discretion of RejectedExecutionHandler, if task cannot be accepted for execution
NullPointerException - if command is null

shutdown

public void shutdown()
Initiates an orderly shutdown in which previously submitted tasks are executed, but no new tasks will be accepted. Invocation has no additional effect if already shut down.

Throws:
SecurityException - if a security manager exists and shutting down this ExecutorService may manipulate threads that the caller is not permitted to modify because it does not hold RuntimePermission("modifyThread"), or the security manager's checkAccess method denies access.

shutdownNow

public List shutdownNow()
Attempts to stop all actively executing tasks, halts the processing of waiting tasks, and returns a list of the tasks that were awaiting execution.

This implementation cancels tasks via Thread.interrupt(), so if any tasks mask or fail to respond to interrupts, they may never terminate.

Returns:
list of tasks that never commenced execution
Throws:
SecurityException - if a security manager exists and shutting down this ExecutorService may manipulate threads that the caller is not permitted to modify because it does not hold RuntimePermission("modifyThread"), or the security manager's checkAccess method denies access.

isShutdown

public boolean isShutdown()


isTerminating

public boolean isTerminating()
Returns true if this executor is in the process of terminating after shutdown or shutdownNow but has not completely terminated. This method may be useful for debugging. A return of true reported a sufficient period after shutdown may indicate that submitted tasks have ignored or suppressed interruption, causing this executor not to properly terminate.

Returns:
true if terminating but not yet terminated.

isTerminated

public boolean isTerminated()


awaitTermination

public boolean awaitTermination(long timeout,
                                TimeUnit unit)
                         throws InterruptedException


finalize

protected void finalize()
Invokes shutdown when this executor is no longer referenced.

Overrides:
finalize in class Object

setWorkFactory

public void setWorkFactory(WorkFactory workFactory)
Sets the thread factory used to create new threads.

Parameters:
workFactory - the new thread factory
Throws:
NullPointerException - if workFactory is null
See Also:
getWorkFactory()

setWorkManager

public void setWorkManager(WorkManager workManager)


getWorkFactory

public WorkFactory getWorkFactory()
Returns the thread factory used to create new threads.

Returns:
the current thread factory
See Also:
setWorkFactory(com.bea.wlevs.ede.WorkFactory)

setRejectedExecutionHandler

public void setRejectedExecutionHandler(RejectedExecutionHandler handler)
Sets a new handler for unexecutable tasks.

Parameters:
handler - the new handler
Throws:
NullPointerException - if handler is null
See Also:
getRejectedExecutionHandler()

getRejectedExecutionHandler

public RejectedExecutionHandler getRejectedExecutionHandler()
Returns the current handler for unexecutable tasks.

Returns:
the current handler
See Also:
setRejectedExecutionHandler(com.bea.wlevs.ede.RejectedExecutionHandler)

getQueue

public BlockingQueue getQueue()
Returns the task queue used by this executor. Access to the task queue is intended primarily for debugging and monitoring. This queue may be in active use. Retrieving the task queue does not prevent queued tasks from executing.
Specified by:
getQueue in interface BlockingQueueExecutor

Returns:
the task queue

remove

public boolean remove(Runnable task)
Removes this task from the executor's internal queue if it is present, thus causing it not to be run if it has not already started.

This method may be useful as one part of a cancellation scheme. It may fail to remove tasks that have been converted into other forms before being placed on the internal queue. For example, a task entered using submit might be converted into a form that maintains Future status. However, in such cases, method purge() may be used to remove those Futures that have been cancelled.

Parameters:
task - the task to remove
Returns:
true if the task was removed

purge

public void purge()
Tries to remove from the work queue all Future tasks that have been cancelled. This method can be useful as a storage reclamation operation, that has no other impact on functionality. Cancelled tasks are never executed, but may accumulate in work queues until worker threads can actively remove them. Invoking this method instead tries to remove them now. However, this method may fail to remove tasks in the presence of interference by other threads.


setCorePoolSize

public void setCorePoolSize(int corePoolSize)
Sets the core number of threads. This overrides any value set in the constructor. If the new value is smaller than the current value, excess existing threads will be terminated when they next become idle. If larger, new threads will, if needed, be started to execute any queued tasks.

Parameters:
corePoolSize - the new core size
Throws:
IllegalArgumentException - if corePoolSize less than zero
See Also:
getCorePoolSize()

getCorePoolSize

public int getCorePoolSize()
Returns the core number of threads.

Returns:
the core number of threads
See Also:
setCorePoolSize(int)

prestartCoreThread

public boolean prestartCoreThread()
Starts a core thread, causing it to idly wait for work. This overrides the default policy of starting core threads only when new tasks are executed. This method will return false if all core threads have already been started.

Returns:
true if a thread was started

prestartAllCoreThreads

public int prestartAllCoreThreads()
Starts all core threads, causing them to idly wait for work. This overrides the default policy of starting core threads only when new tasks are executed.

Returns:
the number of threads started.

setMaximumPoolSize

public void setMaximumPoolSize(int maximumPoolSize)
Sets the maximum allowed number of threads. This overrides any value set in the constructor. If the new value is smaller than the current value, excess existing threads will be terminated when they next become idle.

Parameters:
maximumPoolSize - the new maximum
Throws:
IllegalArgumentException - if maximumPoolSize less than zero or the core pool size
See Also:
getMaximumPoolSize()

getMaximumPoolSize

public int getMaximumPoolSize()
Returns the maximum allowed number of threads.

Returns:
the maximum allowed number of threads
See Also:
setMaximumPoolSize(int)

setKeepAliveTime

public void setKeepAliveTime(long time,
                             TimeUnit unit)
Sets the time limit for which threads may remain idle before being terminated. If there are more than the core number of threads currently in the pool, after waiting this amount of time without processing a task, excess threads will be terminated. This overrides any value set in the constructor.

Parameters:
time - the time to wait. A time value of zero will cause excess threads to terminate immediately after executing tasks.
unit - the time unit of the time argument
Throws:
IllegalArgumentException - if time less than zero
See Also:
getKeepAliveTime(java.util.concurrent.TimeUnit)

getKeepAliveTime

public long getKeepAliveTime(TimeUnit unit)
Returns the thread keep-alive time, which is the amount of time which threads in excess of the core pool size may remain idle before being terminated.

Parameters:
unit - the desired time unit of the result
Returns:
the time limit
See Also:
setKeepAliveTime(long, java.util.concurrent.TimeUnit)

getPoolSize

public int getPoolSize()
Returns the current number of threads in the pool.

Returns:
the number of threads

getActiveCount

public int getActiveCount()
Returns the approximate number of threads that are actively executing tasks.

Returns:
the number of threads

getLargestPoolSize

public int getLargestPoolSize()
Returns the largest number of threads that have ever simultaneously been in the pool.

Returns:
the number of threads

getTaskCount

public long getTaskCount()
Returns the approximate total number of tasks that have been scheduled for execution. Because the states of tasks and threads may change dynamically during computation, the returned value is only an approximation, but one that does not ever decrease across successive calls.

Returns:
the number of tasks

getCompletedTaskCount

public long getCompletedTaskCount()
Returns the approximate total number of tasks that have completed execution. Because the states of tasks and threads may change dynamically during computation, the returned value is only an approximation, but one that does not ever decrease across successive calls.

Returns:
the number of tasks

beforeExecute

protected void beforeExecute(Work w,
                             Runnable r)
Method invoked prior to executing the given Runnable in the given thread. This method is invoked by thread t that will execute task r, and may be used to re-initialize ThreadLocals, or to perform logging. Note: To properly nest multiple overridings, subclasses should generally invoke super.beforeExecute at the end of this method.

Parameters:
t - the thread that will run task r.
r - the task that will be executed.

afterExecute

protected void afterExecute(Runnable r,
                            Throwable t)
Method invoked upon completion of execution of the given Runnable. This method is invoked by the thread that executed the task. If non-null, the Throwable is the uncaught exception that caused execution to terminate abruptly. Note: To properly nest multiple overridings, subclasses should generally invoke super.afterExecute at the beginning of this method.

Parameters:
r - the runnable that has completed.
t - the exception that caused termination, or null if execution completed normally.

terminated

protected void terminated()
Method invoked when the Executor has terminated. Default implementation does nothing. Note: To properly nest multiple overridings, subclasses should generally invoke super.terminated within this method.