java定时器

java的定时器有四种实现方式

• 使用java的timer类，这种方式可以灵活的控制定时器的开启关闭
• 使用线程和线程池的方法，这种方式对于关闭定时器是不优雅的，甚至可能出错
• 使用spring注解来启动定时任务，使用起来简单，但是关闭起来不方便，得配合那些监听器
• 使用quartz框架来解决，很专业，也很重。

简单记录一下这些方式的用法

java Timer

package com.yezi_tool.demo_basic.test;import org.springframework.stereotype.Component;import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;@Component
public class TimerTest {private Integer count = 0;public TimerTest() {testTimer2();}public void testTimer2() {Timer timer = new Timer();MyTask myTask = new MyTask();timer.schedule(myTask, 0, 1000);}private class MyTask extends TimerTask {@Overridepublic void run() {try {//do SomethingSystem.out.println(new Date().toString() + ": " + count);count++;} catch (Exception e) {e.printStackTrace();}}}}

Spring 的@Scheduled

@Component
@EnableScheduling
public class ScheduleTest {private int count = 0;/*** 每3秒钟执行一次*/@Scheduled(cron = "*/3 * * * * ?")public void test1() {System.out.println(count + "：" + (new Date()).toString());count++;}
}

java线程池

直接用线程sleep方法，也可以扩展使用线程池，本质都是不停的循环+sleep

package com.yezi_tool.demo_basic.test;import org.springframework.stereotype.Component;import java.util.Date;@Component
public class ThreadTest {private Integer count = 0;public ThreadTest() {test1();}public void test1() {new Thread(() -> {while (count < 10) {System.out.println(new Date().toString() + ": " + count);count++;try {Thread.sleep(3000);} catch (InterruptedException e) {e.printStackTrace();}}}).start();}
}

ScheduledTask + runnable,使用专门的定时任务线程池，但是关闭不优雅，根据情况使用

package com.yezi_tool.demo_basic.test;import org.springframework.scheduling.TaskScheduler;
import org.springframework.stereotype.Component;import java.util.Date;@Component
public class ThreadTest {private Integer count = 0;private final TaskScheduler taskScheduler;public ThreadTest(TaskScheduler taskScheduler) {this.taskScheduler = taskScheduler;test3();}public void test3() {taskScheduler.scheduleAtFixedRate(() -> {System.out.println(new Date().toString() + ": " + count);count++;}, 3000);}
}

package com.yezi_tool.demo_basic.test;import org.springframework.scheduling.TaskScheduler;
import org.springframework.scheduling.support.CronTrigger;
import org.springframework.stereotype.Component;import java.util.Date;@Component
public class ThreadTest {private Integer count = 0;private final TaskScheduler taskScheduler;public ThreadTest(TaskScheduler taskScheduler) {this.taskScheduler = taskScheduler;test4();}public void test4() {taskScheduler.schedule(() -> {System.out.println(new Date().toString() + ": " + count);count++;}, new CronTrigger("0 0 1 * * ?"));}
}

Quartz

quartz是一个完整的专门做定时任务的框架，支持分布式，事务等复杂功能，具体结构如下：

• job用来定义任务
• trigger用来设置任务执行时间
• scheduler：用来管理任务的执行，暂停和停止
• 此外重要的监视器功能JobListener、TriggerListener、SchedulerListener，能够监视上面三个类的生命周期
  
  quartz中文说明
  quarts英文官网
  quarts中文教程

public class HelloJob implements Job {@Overridepublic void execute(JobExecutionContext context) throws JobExecutionException {Object tv1 = context.getTrigger().getJobDataMap().get("t1");Object tv2 = context.getTrigger().getJobDataMap().get("t2");Object jv1 = context.getJobDetail().getJobDataMap().get("j1");Object jv2 = context.getJobDetail().getJobDataMap().get("j2");Object sv = null;try {sv = context.getScheduler().getContext().get("skey");} catch (SchedulerException e) {e.printStackTrace();}System.out.println(tv1+":"+tv2);System.out.println(jv1+":"+jv2);System.out.println(sv);System.out.println("hello:"+LocalDateTime.now());}}public class Test {public static void main(String[] args) throws SchedulerException {//创建一个schedulerScheduler scheduler = StdSchedulerFactory.getDefaultScheduler();scheduler.getContext().put("skey", "svalue");//创建一个TriggerTrigger trigger = TriggerBuilder.newTrigger().withIdentity("trigger1", "group1").usingJobData("t1", "tv1").withSchedule(SimpleScheduleBuilder.simpleSchedule().withIntervalInSeconds(3).repeatForever()).build();trigger.getJobDataMap().put("t2", "tv2");//创建一个jobJobDetail job = JobBuilder.newJob(HelloJob.class).usingJobData("j1", "jv1").withIdentity("myjob", "mygroup").build();job.getJobDataMap().put("j2", "jv2");//注册trigger并启动schedulerscheduler.scheduleJob(job,trigger);scheduler.start();}}