Package org.qiunet.utils.timer.executor

Class DScheduledThreadPoolExecutor

java.lang.Object
java.util.concurrent.AbstractExecutorService
org.qiunet.utils.timer.executor.DThreadPoolExecutor
org.qiunet.utils.timer.executor.DScheduledThreadPoolExecutor
All Implemented Interfaces:
Executor, ExecutorService, ScheduledExecutorService
public class DScheduledThreadPoolExecutor extends DThreadPoolExecutor implements ScheduledExecutorService
A DThreadPoolExecutor that can additionally schedule commands to run after a given delay, or to execute periodically. This class is preferable to Timer when multiple worker threads are needed, or when the additional flexibility or capabilities of DThreadPoolExecutor (which this class extends) are required.

Delayed tasks execute no sooner than they are enabled, but without any real-time guarantees about when, after they are enabled, they will commence. Tasks scheduled for exactly the same execution time are enabled in first-in-first-out (FIFO) order of submission.

When a submitted task is cancelled before it is run, execution is suppressed. By default, such a cancelled task is not automatically removed from the work queue until its delay elapses. While this enables further inspection and monitoring, it may also cause unbounded retention of cancelled tasks. To avoid this, set setRemoveOnCancelPolicy(boolean) to true, which causes tasks to be immediately removed from the work queue at time of cancellation.

Successive executions of a task scheduled via scheduleAtFixedRate or scheduleWithFixedDelay do not overlap. While different executions may be performed by different threads, the effects of prior executions happen-before those of subsequent ones.

While this class inherits from DThreadPoolExecutor, a fewD of the inherited tuning methods are not useful for it. In particular, because it acts as a fixed-sized pool using corePoolSize threads and an unbounded queue, adjustments to maximumPoolSize have no useful effect. Additionally, it is almost never a good idea to set corePoolSize to zero or use allowCoreThreadTimeOut because this may leave the pool without threads to handle tasks once they become eligible to run.

Extension notes: This class overrides the execute and submit methods to generate internal ScheduledFuture objects to control per-task delays and scheduling. To preserve functionality, any further overrides of these methods in subclasses must invoke superclass versions, which effectively disables additional task customization. However, this class provides alternative protected extension method decorateTask (one version each for Runnable and Callable) that can be used to customize the concrete task types used to execute commands entered via execute, submit, schedule, scheduleAtFixedRate, and scheduleWithFixedDelay. By default, a ScheduledThreadPoolExecutor uses a task type extending FutureTask. However, this may be modified or replaced using subclasses of the form: 

 
 public class CustomScheduledExecutor extends ScheduledThreadPoolExecutor {

   static class CustomTask<V> implements RunnableScheduledFuture<V> { ... }

   protected <V> RunnableScheduledFuture<V> decorateTask(
                Runnable r, RunnableScheduledFuture<V> task) {
       return new CustomTask<V>(r, task);
   }

   protected <V> RunnableScheduledFuture<V> decorateTask(
                Callable<V> c, RunnableScheduledFuture<V> task) {
       return new CustomTask<V>(c, task);
   }
   // ... add constructors, etc.
 }
Since:
1.5
Author:
Doug Lea

  • Constructor Details

    • DScheduledThreadPoolExecutor

      public DScheduledThreadPoolExecutor(int delay, TimeUnit unit)
      Creates a new ScheduledThreadPoolExecutor with the given delay check time.
      Parameters:
      delay - the number of delay for Queue check
      Throws:
      IllegalArgumentException - if corePoolSize < 0

    • DScheduledThreadPoolExecutor

      public DScheduledThreadPoolExecutor()
      Creates a new ScheduledThreadPoolExecutor with the given delay check millis.
      Throws:
      IllegalArgumentException - if corePoolSize < 0

    • DScheduledThreadPoolExecutor

      public DScheduledThreadPoolExecutor(long delayCheckMillis)
      Creates a new ScheduledThreadPoolExecutor with the given delay check millis.
      Parameters:
      delayCheckMillis - the number of delay for Queue check
      Throws:
      IllegalArgumentException - if corePoolSize < 0

    • DScheduledThreadPoolExecutor

      public DScheduledThreadPoolExecutor(int corePoolSize, long delayCheckMillis)
      Creates a new DScheduledThreadPoolExecutor with the given core pool size.
      Parameters:
      corePoolSize - the number of threads to keep in the pool, even if they are idle, unless allowCoreThreadTimeOut is set
      Throws:
      IllegalArgumentException - if corePoolSize < 0

    • DScheduledThreadPoolExecutor

      public DScheduledThreadPoolExecutor(int corePoolSize, long delayCheckMillis, ThreadFactory threadFactory)
      Creates a new DScheduledThreadPoolExecutor with the given initial parameters.
      Parameters:
      corePoolSize - the number of threads to keep in the pool, even if they are idle, unless allowCoreThreadTimeOut is set
      threadFactory - the factory to use when the executor creates a new thread
      Throws:
      IllegalArgumentException - if corePoolSize < 0
      NullPointerException - if threadFactory is null

    • DScheduledThreadPoolExecutor

      public DScheduledThreadPoolExecutor(int corePoolSize, long delayCheckMillis, DRejectedExecutionHandler handler)
      Creates a new DScheduledThreadPoolExecutor with the given initial parameters.
      Parameters:
      corePoolSize - the number of threads to keep in the pool, even if they are idle, unless allowCoreThreadTimeOut is set
      handler - the handler to use when execution is blocked because the thread bounds and queue capacities are reached
      Throws:
      IllegalArgumentException - if corePoolSize < 0
      NullPointerException - if handler is null

    • DScheduledThreadPoolExecutor

      public DScheduledThreadPoolExecutor(int corePoolSize, long delayCheckMillis, ThreadFactory threadFactory, DRejectedExecutionHandler handler)
      Creates a new DScheduledThreadPoolExecutor with the given initial parameters.
      Parameters:
      corePoolSize - the number of threads to keep in the pool, even if they are idle, unless allowCoreThreadTimeOut is set
      threadFactory - the factory to use when the executor creates a new thread
      handler - the handler to use when execution is blocked because the thread bounds and queue capacities are reached
      Throws:
      IllegalArgumentException - if corePoolSize < 0
      NullPointerException - if threadFactory or handler is null

  • Method Details

    • decorateTask

      protected <V> RunnableScheduledFuture<V> decorateTask(Runnable runnable, RunnableScheduledFuture<V> task)
      Modifies or replaces the task used to execute a runnable. This method can be used to override the concrete class used for managing internal tasks. The default implementation simply returns the given task.
      Type Parameters:
      V - the type of the task's result
      Parameters:
      runnable - the submitted Runnable
      task - the task created to execute the runnable
      Returns:
      a task that can execute the runnable
      Since:
      1.6

    • decorateTask

      protected <V> RunnableScheduledFuture<V> decorateTask(Callable<V> callable, RunnableScheduledFuture<V> task)
      Modifies or replaces the task used to execute a callable. This method can be used to override the concrete class used for managing internal tasks. The default implementation simply returns the given task.
      Type Parameters:
      V - the type of the task's result
      Parameters:
      callable - the submitted Callable
      task - the task created to execute the callable
      Returns:
      a task that can execute the callable
      Since:
      1.6

    • schedule

      public ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit)
      Specified by:
      schedule in interface ScheduledExecutorService
      Throws:
      RejectedExecutionException
      NullPointerException

    • schedule

      public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit)
      Specified by:
      schedule in interface ScheduledExecutorService
      Throws:
      RejectedExecutionException
      NullPointerException

    • scheduleAtFixedRate

      public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit)
      Specified by:
      scheduleAtFixedRate in interface ScheduledExecutorService
      Throws:
      RejectedExecutionException
      NullPointerException
      IllegalArgumentException

    • scheduleWithFixedDelay

      public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit)
      Specified by:
      scheduleWithFixedDelay in interface ScheduledExecutorService
      Throws:
      RejectedExecutionException
      NullPointerException
      IllegalArgumentException

    • execute

      public void execute(Runnable command)
      Executes command with zero required delay. This has effect equivalent to schedule(command, 0, anyUnit). Note that inspections of the queue and of the list returned by shutdownNow will access the zero-delayed ScheduledFuture, not the command itself.

      A consequence of the use of ScheduledFuture objects is that afterExecute is always called with a null second Throwable argument, even if the command terminated abruptly. Instead, the Throwable thrown by such a task can be obtained via Future.get().

      Specified by:
      execute in interface Executor
      Overrides:
      execute in class DThreadPoolExecutor
      Parameters:
      command - the task to execute
      Throws:
      RejectedExecutionException - at discretion of RejectedExecutionHandler, if the task cannot be accepted for execution because the executor has been shut down
      NullPointerException - if command is null

    • submit

      public Future<?> submit(Runnable task)
      Specified by:
      submit in interface ExecutorService
      Overrides:
      submit in class AbstractExecutorService
      Throws:
      RejectedExecutionException
      NullPointerException

    • submit

      public <T> Future<T> submit(Runnable task, T result)
      Specified by:
      submit in interface ExecutorService
      Overrides:
      submit in class AbstractExecutorService
      Throws:
      RejectedExecutionException
      NullPointerException

    • submit

      public <T> Future<T> submit(Callable<T> task)
      Specified by:
      submit in interface ExecutorService
      Overrides:
      submit in class AbstractExecutorService
      Throws:
      RejectedExecutionException
      NullPointerException

    • setContinueExistingPeriodicTasksAfterShutdownPolicy

      public void setContinueExistingPeriodicTasksAfterShutdownPolicy(boolean value)
      Sets the policy on whether to continue executing existing periodic tasks even when this executor has been shutdown. In this case, these tasks will only terminate upon shutdownNow or after setting the policy to false when already shutdown. This value is by default false.
      Parameters:
      value - if true, continue after shutdown, else don't
      See Also:

    • getContinueExistingPeriodicTasksAfterShutdownPolicy

      public boolean getContinueExistingPeriodicTasksAfterShutdownPolicy()
      Gets the policy on whether to continue executing existing periodic tasks even when this executor has been shutdown. In this case, these tasks will only terminate upon shutdownNow or after setting the policy to false when already shutdown. This value is by default false.
      Returns:
      true if will continue after shutdown
      See Also:

    • setExecuteExistingDelayedTasksAfterShutdownPolicy

      public void setExecuteExistingDelayedTasksAfterShutdownPolicy(boolean value)
      Sets the policy on whether to execute existing delayed tasks even when this executor has been shutdown. In this case, these tasks will only terminate upon shutdownNow, or after setting the policy to false when already shutdown. This value is by default true.
      Parameters:
      value - if true, execute after shutdown, else don't
      See Also:

    • getExecuteExistingDelayedTasksAfterShutdownPolicy

      public boolean getExecuteExistingDelayedTasksAfterShutdownPolicy()
      Gets the policy on whether to execute existing delayed tasks even when this executor has been shutdown. In this case, these tasks will only terminate upon shutdownNow, or after setting the policy to false when already shutdown. This value is by default true.
      Returns:
      true if will execute after shutdown
      See Also:

    • setRemoveOnCancelPolicy

      public void setRemoveOnCancelPolicy(boolean value)
      Sets the policy on whether cancelled tasks should be immediately removed from the work queue at time of cancellation. This value is by default false.
      Parameters:
      value - if true, remove on cancellation, else don't
      Since:
      1.7
      See Also:

    • getRemoveOnCancelPolicy

      public boolean getRemoveOnCancelPolicy()
      Gets the policy on whether cancelled tasks should be immediately removed from the work queue at time of cancellation. This value is by default false.
      Returns:
      true if cancelled tasks are immediately removed from the queue
      Since:
      1.7
      See Also:

    • 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.

      This method does not wait for previously submitted tasks to complete execution. Use awaitTermination to do that.

      If the ExecuteExistingDelayedTasksAfterShutdownPolicy has been set false, existing delayed tasks whose delays have not yet elapsed are cancelled. And unless the ContinueExistingPeriodicTasksAfterShutdownPolicy has been set true, future executions of existing periodic tasks will be cancelled.

      Specified by:
      shutdown in interface ExecutorService
      Overrides:
      shutdown in class DThreadPoolExecutor
      Throws:
      SecurityException

    • shutdownNow

      public List<Runnable> 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 method does not wait for actively executing tasks to terminate. Use awaitTermination to do that.

      There are no guarantees beyond best-effort attempts to stop processing actively executing tasks. This implementation cancels tasks via Thread.interrupt(), so any task that fails to respond to interrupts may never terminate.

      Specified by:
      shutdownNow in interface ExecutorService
      Overrides:
      shutdownNow in class DThreadPoolExecutor
      Returns:
      list of tasks that never commenced execution. Each element of this list is a ScheduledFuture, including those tasks submitted using execute, which are for scheduling purposes used as the basis of a zero-delay ScheduledFuture.
      Throws:
      SecurityException

    • getQueue

      public BlockingQueue<Runnable> getQueue()
      Returns the task queue used by this executor. Each element of this queue is a ScheduledFuture, including those tasks submitted using execute which are for scheduling purposes used as the basis of a zero-delay ScheduledFuture. Iteration over this queue is not guaranteed to traverse tasks in the order in which they will execute.
      Overrides:
      getQueue in class DThreadPoolExecutor
      Returns:
      the task queue