spring源码分析之定时任务概述

 Spring框架提供了TaskExcutor的异步执行和TashScheduler的任务定时执行接口，同样spring也提供了线程池或者CommonJ的代理。

TaskExecutor的类型

SimpleAsyncTaskExecutor，没有复用线程，当触发时仅仅启动一个新的线程。支持并发。

SyncTaskExecutor，同步触发，主要用来不需要多线程的情况，例如测试用例

ConcurrentTaskExecutor，java.util.concurrent.Executor的适配器，作为ThreadPoolTaskExecutor的替代品，很少使用，但如果ThreadPoolTaskExecutor不能满足你的需求，可以考虑使用它。

SimpleThreadPoolTaskExecutor，Quartz的SimpleThreadPool子类实现，它监听spring生命周期的callback，主要用来在quartz和非quartz组件共享线程池时。

ThreadPoolTaskExecutor，常用的TaskExecutor实现类。

WorkManagerTaskExecutor，使用了CommJ的WorkMannager作为它的实现，它提供了在spring contxt中建立一个CommonJ WorkManger的便利主类，类似于SimpleThreadPoolTaskExecutor。

注：CommonJ是BEA和IBM开发的

TaskExecutor使用示例：

import org.springframework.core.task.TaskExecutor;

public class TaskExecutorExample {

    private class MessagePrinterTask implements Runnable {

        private String message;

        public MessagePrinterTask(String message) {
            this.message = message;
        }

        public void run() {
            System.out.println(message);
        }

    }

    private TaskExecutor taskExecutor;

    public TaskExecutorExample(TaskExecutor taskExecutor) {
        this.taskExecutor = taskExecutor;
    }

    public void printMessages() {
        for(int i = 0; i < 25; i++) {
            taskExecutor.execute(new MessagePrinterTask("Message" + i));
        }
    }

}

配置文件：

<bean id="taskExecutor" class="org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor">
    <property name="corePoolSize" value="5" />
    <property name="maxPoolSize" value="10" />
    <property name="queueCapacity" value="25" />
</bean>

<bean id="taskExecutorExample" class="TaskExecutorExample">
    <constructor-arg ref="taskExecutor" />
</bean>

使用Quartz Scheduler

1. 使用JobDetailFactoryBean

<bean name="exampleJob" class="org.springframework.scheduling.quartz.JobDetailFactoryBean">
    <property name="jobClass" value="example.ExampleJob"/>
    <property name="jobDataAsMap">
        <map>
            <entry key="timeout" value="5"/>
        </map>
    </property>
</bean>

测试类

package example;

public class ExampleJob extends QuartzJobBean {

    private int timeout;

    /**
     * Setter called after the ExampleJob is instantiated
     * with the value from the JobDetailFactoryBean (5)
     */
    public void setTimeout(int timeout) {
        this.timeout = timeout;
    }

    protected void executeInternal(JobExecutionContext ctx) throws JobExecutionException {
        // do the actual work
    }

}

2. 使用MethodInvokingJobDetailFactoryBean

 配置文件

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

对应的方法

public class ExampleBusinessObject {

    // properties and collaborators

    public void doIt() {
        // do the actual work
    }
}

<bean id="exampleBusinessObject" class="examples.ExampleBusinessObject"/>

有状态的job，一个任务没完成之前，相同任务的下个不会执行

<bean id="jobDetail" class="org.springframework.scheduling.quartz.MethodInvokingJobDetailFactoryBean">
    <property name="targetObject" ref="exampleBusinessObject"/>
    <property name="targetMethod" value="doIt"/>
    <property name="concurrent" value="false"/>
</bean>

3. 使用triggers 和SchedulerFactoryBean包装job

两种类型的TriggerFactoryBean，分别是SimpleTriggerFactoryBean和CronTriggerFactoryBean

<bean id="simpleTrigger" class="org.springframework.scheduling.quartz.SimpleTriggerFactoryBean">
    <!-- see the example of method invoking job above -->
    <property name="jobDetail" ref="jobDetail"/>
    <!-- 10 seconds -->
    <property name="startDelay" value="10000"/>
    <!-- repeat every 50 seconds -->
    <property name="repeatInterval" value="50000"/>
</bean>

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

建立SchedulerFactoryBean

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

参考文献：

【1】http://docs.spring.io/spring/docs/current/spring-framework-reference/html/scheduling.html

【2】http://www.cnblogs.com/davidwang456/p/4237895.html