Timing task framework the Quartz -----

A. What is Quartz

By the java developed to perform regular tasks, but compared to similar java.util.Timer Timer, quartz adds a lot of features:

Persistent job - is to keep the state of the timing schedule

Job Management - Effective management of scheduled jobs

(1) First, we need to define implement a timer function interface, called Task (or Job), such as task (Job) regularly send messages, restart the machine's task (Job), Coupons expire to send text messages to remind the task (Job), implement the following interfaces:

(2) Once you have the task, but also a possible trigger to perform tasks trigger, trigger Traigger most basic function is to specify the job execution time, the execution interval, run times, etc.

(3) Once you have job and trigger, how to combine the two, that is, how to specify the Trigger to perform certain job? This requires a schedule, be responsible for implementing this feature

The above is part of quartz three basic components:

1. Scheduler: Scheduler

2. Mission: JobDetail

3. Trigger: Trigger includes SimpleTrigger and CroTrigger

Two, Quartz Demo build

Let's take advantage of Quartz build a basic Demo.

1, introducing dependent jar package:

<dependency>
    <groupId>org.quartz-scheduler</groupId>
    <artifactId>quartz</artifactId>
    <version>2.3.0</version>
</dependency>

2. Configure the information

# 名为：quartz.properties，放置在classpath下，如果没有此配置则按默认配置启动
# 指定调度器名称，非实现类
org.quartz.scheduler.instanceName = DefaultQuartzScheduler04
# 指定线程池实现类
org.quartz.threadPool.class = org.quartz.simpl.SimpleThreadPool
# 线程池线程数量
org.quartz.threadPool.threadCount = 10 
# 优先级，默认5
org.quartz.threadPool.threadPriority = 5
# 非持久化job
org.quartz.jobStore.class = org.quartz.simpl.RAMJobStore

3、新建一个能够打印任意内容的Job：

public class PrintWordsJob implements Job{

    @Override
    public void execute(JobExecutionContext jobExecutionContext) throws JobExecutionException {
        String printTime = new SimpleDateFormat("yy-MM-dd HH-mm-ss").format(new Date());
        System.out.println("PrintWordsJob start at:" + printTime + ", prints: Hello Job-" + new Random().nextInt(100));

    }
}

4、创建Schedule，执行任务：

public class MyScheduler {

    public static void main(String[] args) throws SchedulerException, InterruptedException {
        // 1、创建调度器Scheduler
        SchedulerFactory schedulerFactory = new StdSchedulerFactory();
        Scheduler scheduler = schedulerFactory.getScheduler();
        // 2、创建JobDetail实例，并与PrintWordsJob类绑定(Job执行内容)
        JobDetail jobDetail = JobBuilder.newJob(PrintWordsJob.class)
                                        .withIdentity("job1", "group1").build();
        // 3、构建Trigger实例,每隔1s执行一次
        Trigger trigger = TriggerBuilder.newTrigger().withIdentity("trigger1", "triggerGroup1")
                .startNow()//立即生效
                .withSchedule(SimpleScheduleBuilder.simpleSchedule()
                .withIntervalInSeconds(1)//每隔1s执行一次
                .repeatForever()).build();//一直执行

        //4、执行
        scheduler.scheduleJob(jobDetail, trigger);
        System.out.println("--------scheduler start ! ------------");
        scheduler.start();

        //睡眠
        TimeUnit.MINUTES.sleep(1);
        scheduler.shutdown();
        System.out.println("--------scheduler shutdown ! ------------");

    }
}

运行程序，可以看到程序每隔1s会打印出内容，且在一分钟后结束：

三、Quartz核心详解

下面就程序中出现的几个参数，看一下Quartz框架中的几个重要参数：

Job和JobDetail
JobExecutionContext
JobDataMap
Trigger、SimpleTrigger、CronTrigger

1，JobDetail用来绑定job，为job实例提供许多属性：

. name

. group

. jobclass

. jobDataMap

　　jobDetail绑定指定的job，每次Scheduler调度执行一个job时，首先会拿到对印的job，然后先创建该job实例，再去执行再去执行job中的execute（）的内容，任务执行结束后，关联的job对象实例会被释放，且会被jvm GC清除

　　jobDetail定义的是任务数据，而真正的执行逻辑实在job中。

　　这是应为任务时有可能并发执行的，如果Scheduler直接使用job，就会存在对同一个job实例并发访问的问题，而JobDetail & Job 方式，Sheduler每次执行，都会根据JobDetail创建一个新的Job实例，这样就可以规避并发访问的问题。

2.JobExecutionContext
　　JobExecutionContext中包含了Quartz运行时的环境以及Job本身的详细数据信息。
当Schedule调度执行一个Job的时候，就会将JobExecutionContext传递给该Job的execute()中，Job就可以通过JobExecutionContext对象获取信息。

3.JobDataMap

　　JobDataMap实现了JDK的Map接口，可以以Key-Value的形式存储数据。
　　JobDetail、Trigger都可以使用JobDataMap来设置一些参数或信息，
　　Job执行execute()方法的时候，JobExecutionContext可以获取到JobExecutionContext中的信息：

4.Trigger、SimpleTrigger、CronTrigger

(1).trigger是Quartz的触发器，会去通知Scheduler何时去执行对应job

new Trigger().startAt():表示触发器首次被触发的时间;

new Trigger().endAt():表示触发器结束触发的时间;

(2) SimpleTrigger：可以实现在一个时间段内执行一次作业任务或一个时间段内多次执行作业任务。

(3) CronTrigger：CroTrigger功能非常强大，是基于日历的作业调度，而SimpleTrigger是精准指定间隔，所以相比SimpleTrigger，CronTrigger更加常用。CroTrigger是基于Cron表达式的，cron表达式格式如下:

  [秒] [分] [小时] [日] [月] [周] [年]

可通过在线生成Cron表达式的工具： http://cron.qqe2.com/ 来生成自己想要的表达式。

下面的代码就实现了每周一到周五上午15:00执行定时任务

public class MyScheduler2 {

    public static void main(String[] args) throws SchedulerException {
        //创建调度器Scheduler
        SchedulerFactory schedulerFactory=new StdSchedulerFactory();
        Scheduler scheduler=schedulerFactory.getScheduler();
        //创建jobDetail实例，并与printWordsJob类绑定（job执行内容）
        JobDetail jobDetail= JobBuilder.newJob(PrintWordsJob.class).usingJobData("jobDetail1","这个job用来测试的")
                .withIdentity("job1","group1").build();
        //构建Trigger实例，每隔一秒执行一次
        //实现程序运行5s后开始执行Job，执行Job 5s后结束执行：
        Date startDate=new Date();
        startDate.setTime(startDate.getTime()+5000);
        Date endDate=new Date();
        endDate.setTime(startDate.getTime()+5000);
        CronTrigger cronTrigger=TriggerBuilder.newTrigger().withIdentity("trigger1", "triggerGroup1")
                .usingJobData("trigger1", "这是jobDetail1的trigger")
                .startNow()
                .startAt(startDate)
                .endAt(endDate)
                .withSchedule(CronScheduleBuilder.cronSchedule("* 00 15 ? * 1/5 2019")).build();

        scheduler.scheduleJob(jobDetail,cronTrigger);
        System.out.println("--------scheduler start ! ------------");
        scheduler.start();
        System.out.println("--------scheduler shutdown ! ------------");


    }
}

原文链接：https://blog.csdn.net/noaman_wgs/article/details/80984873