Saturday, December 12, 2009

Spring3 Features -TaskExecutor & TaskSchedulor

The Spring Framework provides abstractions for asynchronous execution and scheduling of tasks with the TaskExecutor and TaskScheduler interfaces, respectively.
[Download - rename from pdf to rar]
[Attached is the sample code for both –with annotations]

1. TaskExecutor

Spring's TaskExecutor interface is identical to the java.util.concurrent.Executor interface.

ConcurrentTaskExecutor : This implementation is a wrapper for a Java 5 java.util.concurrent.Executor.

ThreadPoolTaskExecutor : Spring's TaskExecutor implementation.

[org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor – Namespace: ]

Parametres : corePoolSize,maxPoolSize,queuecapacity,rejection-policy

The executor will first try to use a free thread if the number of active threads is currently less than the core size. If the core size has been reached, then the task will be added to the queue as long as its capacity has not yet been reached. Only then, if the queue's capacity has been reached, will the executor create a new thread beyond the core size. If the max size has also been reached, then the executor will reject the task.

By default, when a task is rejected, a thread pool executor will throw a TaskRejectedException. CallerRunsPolicy. Instead of throwing an exception or discarding tasks, that policy will simply force the thread that is calling the submit method to run the task itself. The idea is that such a caller will be busy while running that task and not able to submit other tasks immediately. Therefore it provides a simple way to throttle the incoming load while maintaining the limits of the thread pool and queue.

2. TaskScheduler

Spring 3.0 introduces a TaskScheduler with a variety of methods for scheduling tasks to run at some point in the future.

- can be associated with a pool size.

Taskschedulor.schedule() takes a trigger expression based on which tasks will be scheduled.

Annotation Support

Both have very easy annotation support.

@Async - This can be marked on any POJO method

@Scheduled- This annotation can be marked on any POJO method

Just add  in the xml and give respective scheduler or executor as properties.

Currently with spring 3 RC2 and Spring Dm 2.0M6 – I could not use namespace support as they were giving some issues. It could be a BUG and I have raised this issue in the forum.

In the attached sample code instead of using namespace I have used the entire class name.

Namespace should work with Spring 3 RC3 version.

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