SimpleAsyncTaskExecutor (Spring Framework 3.2.1.RELEASE API)
Date: 2013-01-24

org.springframework.core.task

## Class SimpleAsyncTaskExecutor

- java.lang.Object
- - org.springframework.util.CustomizableThreadCreator
  - - org.springframework.core.task.SimpleAsyncTaskExecutor

- All Implemented Interfaces:
    Serializable, Executor, AsyncTaskExecutor, TaskExecutor

      public class SimpleAsyncTaskExecutor
      extends CustomizableThreadCreator
      implements AsyncTaskExecutor, Serializable

  `TaskExecutor` implementation that fires up a new Thread for each task, executing it asynchronously.

  Supports limiting concurrent threads through the "concurrencyLimit" bean property. By default, the number of concurrent threads is unlimited.

  NOTE: This implementation does not reuse threads! Consider a thread-pooling TaskExecutor implementation instead, in particular for executing a large number of short-lived tasks.

  Since:
    2.0
  Author:
    Juergen Hoeller
  See Also:
    `setConcurrencyLimit(int)`, `SyncTaskExecutor`, `ThreadPoolTaskExecutor`, `WorkManagerTaskExecutor`, Serialized Form

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static int` | `NO_CONCURRENCY` Switch concurrency 'off': that is, don't allow any concurrent invocations.
    `static int` | `UNBOUNDED_CONCURRENCY` Permit any number of concurrent invocations: that is, don't throttle concurrency.

    - ### Fields inherited from interface org.springframework.core.task.AsyncTaskExecutor

      `TIMEOUT_IMMEDIATE, TIMEOUT_INDEFINITE`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `SimpleAsyncTaskExecutor()` Create a new SimpleAsyncTaskExecutor with default thread name prefix.
    `SimpleAsyncTaskExecutor(String threadNamePrefix)` Create a new SimpleAsyncTaskExecutor with the given thread name prefix.
    `SimpleAsyncTaskExecutor(ThreadFactory threadFactory)` Create a new SimpleAsyncTaskExecutor with the given external thread factory.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `protected void` | `doExecute(Runnable task)` Template method for the actual execution of a task.
    `void` | `execute(Runnable task)` Executes the given task, within a concurrency throttle if configured (through the superclass's settings).
    `void` | `execute(Runnable task, long startTimeout)` Executes the given task, within a concurrency throttle if configured (through the superclass's settings).
    `int` | `getConcurrencyLimit()` Return the maximum number of parallel accesses allowed.
    `ThreadFactory` | `getThreadFactory()` Return the external factory to use for creating new Threads, if any.
    `boolean` | `isThrottleActive()` Return whether this throttle is currently active.
    `void` | `setConcurrencyLimit(int concurrencyLimit)` Set the maximum number of parallel accesses allowed.
    `void` | `setThreadFactory(ThreadFactory threadFactory)` Specify an external factory to use for creating new Threads, instead of relying on the local properties of this executor.
    `<T> Future<T>` | `submit(Callable<T> task)` Submit a Callable task for execution, receiving a Future representing that task.
    `Future<?>` | `submit(Runnable task)` Submit a Runnable task for execution, receiving a Future representing that task.

    - ### Methods inherited from class org.springframework.util.CustomizableThreadCreator

      `createThread, getDefaultThreadNamePrefix, getThreadGroup, getThreadNamePrefix, getThreadPriority, isDaemon, nextThreadName, setDaemon, setThreadGroup, setThreadGroupName, setThreadNamePrefix, setThreadPriority`

    - ### Methods inherited from class java.lang.Object

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

- - ### Field Detail

    - #### UNBOUNDED_CONCURRENCY

          public static final int UNBOUNDED_CONCURRENCY

      Permit any number of concurrent invocations: that is, don't throttle concurrency.
      See Also:
        Constant Field Values

    - #### NO_CONCURRENCY

          public static final int NO_CONCURRENCY

      Switch concurrency 'off': that is, don't allow any concurrent invocations.
      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### SimpleAsyncTaskExecutor

          public SimpleAsyncTaskExecutor()

      Create a new SimpleAsyncTaskExecutor with default thread name prefix.

    - #### SimpleAsyncTaskExecutor

          public SimpleAsyncTaskExecutor(String threadNamePrefix)

      Create a new SimpleAsyncTaskExecutor with the given thread name prefix.
      Parameters:
        `threadNamePrefix` - the prefix to use for the names of newly created threads

    - #### SimpleAsyncTaskExecutor

          public SimpleAsyncTaskExecutor(ThreadFactory threadFactory)

      Create a new SimpleAsyncTaskExecutor with the given external thread factory.
      Parameters:
        `threadFactory` - the factory to use for creating new Threads

  - ### Method Detail

    - #### setThreadFactory

          public void setThreadFactory(ThreadFactory threadFactory)

      Specify an external factory to use for creating new Threads, instead of relying on the local properties of this executor.

      You may specify an inner ThreadFactory bean or also a ThreadFactory reference obtained from JNDI (on a Java EE 6 server) or some other lookup mechanism.

      See Also:
        `CustomizableThreadCreator.setThreadNamePrefix(java.lang.String)`, `CustomizableThreadCreator.setThreadPriority(int)`

    - #### getThreadFactory

          public final ThreadFactory getThreadFactory()

      Return the external factory to use for creating new Threads, if any.

    - #### setConcurrencyLimit

          public void setConcurrencyLimit(int concurrencyLimit)

      Set the maximum number of parallel accesses allowed. -1 indicates no concurrency limit at all.

      In principle, this limit can be changed at runtime, although it is generally designed as a config time setting. NOTE: Do not switch between -1 and any concrete limit at runtime, as this will lead to inconsistent concurrency counts: A limit of -1 effectively turns off concurrency counting completely.

      See Also:
        `UNBOUNDED_CONCURRENCY`

    - #### getConcurrencyLimit

          public final int getConcurrencyLimit()

      Return the maximum number of parallel accesses allowed.

    - #### isThrottleActive

          public final boolean isThrottleActive()

      Return whether this throttle is currently active.
      Returns:
        `true` if the concurrency limit for this instance is active
      See Also:
        `getConcurrencyLimit()`, `setConcurrencyLimit(int)`

    - #### execute

          public void execute(Runnable task)

      Executes the given task, within a concurrency throttle if configured (through the superclass's settings).
      Specified by:
        `execute` in interface `Executor`
      Specified by:
        `execute` in interface `TaskExecutor`
      Parameters:
        `task` - the `Runnable` to execute (never `null`)
      See Also:
        `doExecute(Runnable)`

    - #### execute

          public void execute(Runnable task,
                     long startTimeout)

      Executes the given task, within a concurrency throttle if configured (through the superclass's settings).

      Executes urgent tasks (with 'immediate' timeout) directly, bypassing the concurrency throttle (if active). All other tasks are subject to throttling.

      Specified by:
        `execute` in interface `AsyncTaskExecutor`
      Parameters:
        `task` - the `Runnable` to execute (never `null`)
        `startTimeout` - the time duration (milliseconds) within which the task is supposed to start. This is intended as a hint to the executor, allowing for preferred handling of immediate tasks. Typical values are `AsyncTaskExecutor.TIMEOUT_IMMEDIATE` or `AsyncTaskExecutor.TIMEOUT_INDEFINITE` (the default as used by `TaskExecutor.execute(Runnable)`).
      See Also:
        `AsyncTaskExecutor.TIMEOUT_IMMEDIATE`, `doExecute(Runnable)`

    - #### submit

          public Future<?> submit(Runnable task)

      Description copied from interface: `AsyncTaskExecutor`
      Submit a Runnable task for execution, receiving a Future representing that task. The Future will return a `null` result upon completion.
      Specified by:
        `submit` in interface `AsyncTaskExecutor`
      Parameters:
        `task` - the `Runnable` to execute (never `null`)
      Returns:
        a Future representing pending completion of the task

    - #### submit

          public <T> Future<T> submit(Callable<T> task)

      Description copied from interface: `AsyncTaskExecutor`
      Submit a Callable task for execution, receiving a Future representing that task. The Future will return the Callable's result upon completion.
      Specified by:
        `submit` in interface `AsyncTaskExecutor`
      Parameters:
        `task` - the `Callable` to execute (never `null`)
      Returns:
        a Future representing pending completion of the task

    - #### doExecute

          protected void doExecute(Runnable task)

      Template method for the actual execution of a task.

      The default implementation creates a new Thread and starts it.

      Parameters:
        `task` - the Runnable to execute
      See Also:
        `setThreadFactory(java.util.concurrent.ThreadFactory)`, `CustomizableThreadCreator.createThread(java.lang.Runnable)`, `Thread.start()`