java定时器学习

一、这个是利用jdk自带的Thread类的sleep方法实现定时执行任务。

package tasker;

import java.util.Date;

public class tasker01 extends Thread {
	private static Date date;

	public static void main(String[] args) {
		while (true) {
			try {
				Thread.sleep((int) (Math.random() * 1000));
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			System.out.println("休眠一秒");
			date = new Date();
			System.out.println(date);
			// 定时执行任务
		}
	}
}

二、利用 Java 自带的定时器任务执行类 java.util.Timer 和 java.util.TimerTask ，实现方式有两种，一种是用java匿名内部类实现，只需一个类即可，关于匿名内部类请参考http://www.cnblogs.com/nerxious/archive/2013/01/25/2876489.html，使用匿名内部类还有个前提条件：必须继承一个父类或实现一个接口。

package tasker;

import java.util.Date;
import java.util.Timer;

public class tasker02 {
	public static void main(String[] args) {

		Timer timer = new Timer();
		timer.schedule(task, 5000, 2000);
	}
	static java.util.TimerTask task = new java.util.TimerTask() {

		@Override
		public void run() {
			System.out.println("i am running");
			Date date = new Date();
			System.out.println(date);
		}
	};

}

　　第二种方式是新建一个类去继承TimerTask类，需要用两个类解决

Tasker类

package tasker;

import java.util.Date;
import java.util.TimerTask;

public class Tasker extends TimerTask{

	@Override
	public void run() {
		System.out.println("i am running");
		Date date=new Date();
		System.out.println(date);
	}

}

main方法类

package tasker;

import java.util.Timer;

public class tasker02 {
	public static void main(String[] args) {

		Timer timer = new Timer();
		timer.schedule(new Tasker(), 5000, 2000);
	}
}

再举个例子

package timer;

import java.util.Timer;
import java.util.TimerTask;

public class TestTimer {
	public static void main(String[] args) {
		System.out.println("About to schedule task.");
		new Reminder(10);
		System.out.println("Task scheduled...");
		Timer timer=new Timer();
		timer.schedule(new TaskTimer(), 3000);
	}
	  public static class Reminder{
		         Timer timer;
		           public Reminder(int sec){
		               timer = new Timer();
		               timer.schedule(new TimerTask(){
		                   public void run(){
		                      System.out.println("Time's up...");
		                       timer.cancel();
		                  }
		               }, sec*1000);
		         }
		      } 

}

package timer;

import java.util.TimerTask;

public class TaskTimer extends TimerTask{

	@Override
	public void run() {
		int m=4;
		if(m==4){
			System.out.println("====");
		}else{
			System.out.println("定时器运行.....");
		}
	}

}

　　

　　

三、使用ScheduledExecutorService类，此类改进了简陋的Timer类，Java提供的Time类可以周期性地或者延期执行任务，但是有时我们需要并行执行同样的任务，这个时候如果创建多个Time对象会给系统带来负担，解决办法是将定时任务放到线程池中执行。Java的ScheduledThreadPoolExecutor类实现了ScheduledExecutorService接口中定义的以不同方法执行任务的方法。

。

package tasker;

import java.util.Date;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class tasker03 {

	public static void main(String[] args) throws InterruptedException {
		ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool(5);

		System.out.println("Current Time = " + new Date());
		for (int i = 0; i < 3; i++) {
			Thread.sleep(1000);
			scheduledThreadPool.scheduleWithFixedDelay(task, 10000,2000, TimeUnit.SECONDS);
		}

		Thread.sleep(30000);

		scheduledThreadPool.shutdown();
		while (!scheduledThreadPool.isTerminated()) {
		}
		System.out.println("Finished all threads");
	}
	static java.util.TimerTask task = new java.util.TimerTask() {

		@Override
		public void run() {
			System.out.println("i am running");
			Date date = new Date();
			System.out.println(date);
		}
	};

}

　　改进版的和多线程有关的定时器，有两个类

WorkerThread类

package tasker;

import java.util.Date;

public class WorkerThread implements Runnable {
	private String command;
	public WorkerThread(){};
	public WorkerThread(String command){
		this.command=command;
	}

	@Override
	public void run() {
		System.out.println(Thread.currentThread().getName()+"start time:"+new Date());
		processCommand();
		System.out.println(Thread.currentThread().getName()+"end time:"+new Date());
	}
	private void processCommand(){
		try {
			Thread.sleep(1000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
	public String toString(){
		return this.command;
	}

}

main类

package tasker;

import java.util.Date;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class tasker03 {

	public static void main(String[] args) throws InterruptedException {
		ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool(5);
		System.out.println("Current Time = " + new Date());
		for (int i = 0; i < 3; i++) {
			Thread.sleep(1000);
			WorkerThread task=new WorkerThread("do something");
			scheduledThreadPool.scheduleWithFixedDelay(task, 10000,2000, TimeUnit.SECONDS);
		}

		Thread.sleep(30000);

		scheduledThreadPool.shutdown();
		while (!scheduledThreadPool.isTerminated()) {
		}
		System.out.println("Finished all threads");
	}

}

四、使用任务调度框架Quartz,官网 http://www.quartz-scheduler.org

在Spring中的用法：

引入jar包

java代码

package com.coalmine.desktop;
import java.text.SimpleDateFormat;
import java.util.Date;
public class QuartzJob {

 public void work() {

  SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
  Date date =  new Date();
  System.out.println(sdf.format(date) + "  执行Quartz定时器");

 }
}

applicationContext.xml配置如下：

<!-- 要调用的工作类 -->
<bean id="quartzJob" class="com.coalmine.desktop.QuartzJob"></bean>

 <!-- 定义调用对象和调用对象的方法 -->
 <bean id="jobtask"   class="org.springframework.scheduling.quartz.MethodInvokingJobDetailFactoryBean">
 	<!-- 调用的类 -->
 	<property name="targetObject">    <ref bean="quartzJob" />   </property>
 	<!-- 调用类中的方法 -->
 	<property name="targetMethod">
 	<value>work</value>
 	</property>
 </bean>
 <!-- 定义触发时间 -->
 <bean id="doTime"   class="org.springframework.scheduling.quartz.CronTriggerBean">
  	<property name="jobDetail">    <ref bean="jobtask" />   </property>
  	<!-- cron表达式 -->
  	<property name="cronExpression">
  	<!-- 第 10秒 隔 5秒执行一次-->
  	<value>10/5 * * * * ?</value>
  	</property>
  </bean>
 <!-- 总管理类 如果将lazy-init='false'那么容器启动就会执行调度程序 -->
  <bean id="startQuertz" lazy-init="false" autowire="no"   class="org.springframework.scheduling.quartz.SchedulerFactoryBean">
  	<property name="triggers">
  		<list>   <ref bean="doTime" />  </list>
  	</property>
  </bean>

启动服务后从第10秒开始每隔5秒执行一次work方法

参考文档：http://www.quartz-scheduler.org/generated/2.2.2/pdf/Quartz_Scheduler_Developer_Guide.pdf

首先创建要执行的类。

然后初始化Scheduler,

SchedulerFactory schedFact = new org.quartz.impl.StdSchedulerFactory();
Scheduler sched = schedFact.getScheduler();
sched.start();

创建job

JobDetail job = newJob(HelloJob.class).withIdentity("myJob", "group1").build();

创建任务执行触发器

Trigger trigger = newTrigger().withIdentity("myTrigger", "group1").startNow()
.withSchedule(simpleSchedule()
.withIntervalInSeconds(40)
.repeatForever())
.build();

安排工作

// Tell quartz to schedule the job using our trigger
sched.scheduleJob(job, trigger);

关闭计划

sched.shutdown(true);

============================================================

The key interfaces of the Quar API are:
Scheduler - the main API for interacting with the Scheduler.
Job - an interface to be implemented by components that you want the Scheduler to execute.
JobDetail - used to define instances of Jobs.
Trigger - a component that defines the schedule upon which a given Job will be executed.
JobBuilder - used to define/build JobDetail instances, which define instances of Jobs.
TriggerBuilder - used to define/build Trigger instances.