Spring3 Features -TaskExecutor & TaskSchedulor

The Spring Framework provides abstractions for asynchronous execution and scheduling of tasks with the TaskExecutor and TaskScheduler interfaces, respectively.

http://docs.google.com/fileview?id=0B-0gqvlsl_VvNTBlMDdmZmUtYWE4Ni00YmRhLTk0ODAtYWNhYjk4OGM5YTk1&hl=en
[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.

http://forum.springsource.org/showthread.php?t=81676

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

Namespace should work with Spring 3 RC3 version.

Scheduling simple Quartz job Using Spring

Currently, Spring supports the Timer, part of the JDK since 1.3, and the Quartz Scheduler (http://www.quartzscheduler.org).
Both schedulers are set up using a FactoryBean with optional references to Timers or Triggers, respectively

Quartx job can be written in several ways

1. Wiring up jobs using triggers and the SchedulerFactoryBean


<bean id="sampleJob" class="com.xyx.SampleJob" />


<bean id="sampleJobTrigger" class="org.springframework.scheduling.quartz.SimpleTriggerBean">
<property name="jobDetail" ref="sampleJob" />
<property name="startDelay" value="10000" />
<property name="repeatInterval" value="50000" />
</bean>

OR

<bean id="sampleJobTrigger" class="org.springframework.scheduling.quartz.CronTriggerBean">
<property name="jobDetail" ref="exampleJob"/>
<!-- run every morning at 6 AM -->
<property name="cronExpression" value="0 0 6 * * ?"/>
</bean>


<bean class="org.springframework.scheduling.quartz.SchedulerFactoryBean">
<property name="triggers">
<list>
<ref bean="sampleJobTrigger" />
</list>
</property>
</bean>



2. Using the JobDetailBean

<bean name="exampleJob" class="org.springframework.scheduling.quartz.JobDetailBean">
<property name="jobClass" value="com.xyx.SampleJob"/>
<property name="jobDataAsMap">
<map>
<entry key="timeout" value="5"/>
</map>
</property>
</bean>


In this case com.xyx.SampleJob has to extend QuartzJobBean.


3. Using the MethodInvokingJobDetailFactoryBean

Often you just need to invoke a method on a specific object. Using the MethodInvokingJobDetailFactoryBean you can do as follows

<bean id="jobDetail" class="org.springframework.scheduling.quartz.MethodInvokingJobDetailFactoryBean">
<property name="targetObject" ref="sampleJob"/>
<property name="targetMethod" value="sampleMethod"/>
</bean>

The above example will result in the sampleMethod() being called on the sampleJob object.

Ref:
http://www.opensymphony.com/quartz.
http://static.springframework.org/spring/docs/1.2.9/reference/scheduling.html

Quartz - For Scheduling

Quartz is a full-featured, open source job scheduling system that can be integrated with,or used along side virtually any J2EE or J2SE application.It can mainly be used for Driving WrkFlow and System maintainance.
It can be integrated with any system with ease.It can perform simple or complicated schedules based on given cron expression.The execution logic can be embedded into simple java classes by implementing certain intefaces.
The job information can either be stored in memory through RAMJobStore or can be stored in relational databases using JDBCJobStore.If RAMJobStore is used whenever the server restarts, previously scheduled data is lost.
For scheduling jobs a scheduler needs to be started and jobs can be added as shown below.
SchedulerFactory schedFact = new org.quartz.impl.StdSchedulerFactory();
Scheduler sched = schedFact.getScheduler();
sched.start();
JobDetail jobDetail = new JobDetail("myJob", null, DumbJob.class);
Trigger trigger = TriggerUtils.makeHourlyTrigger(); // fire every hour trigger.setStartTime(TriggerUtils.getEvenHourDate(new Date())); // start on the next even hour trigger.setName("myTrigger");
sched.scheduleJob(jobDetail, trigger);
Custom job should implement the following interface
Job Interfacepackage org.quartz;
public interface Job {
public void execute(JobExecutionContext context) throws JobExecutionException; }
CronTrigger needs to be used for more complicated schedules.
An example of a complete cron-expression is the string "0 0 12 ? * WED" - which means "every Wednesday at 12:00 pm".