Spring Scheduled定时任务动态修改cron参数

使用spring @scheduled注解可以方便的设定定时任务，但是对于定时参数需要变化的情况就会很不方便，如果要实现更改定时参数，就要停止服务，更改参数，重新部署。
对于这种需求， 可以利用TaskScheduler借口来实现,实现方法有两种

• 启动定时,关闭定时，使用新参数启动定时
• 使用自定义的Trigger启动定时，更改参数

范例代码如下

package schedule;
import java.util.Date;
public class Say implements Runnable {
    @Override
    public void run(){
        System.out.println("" + new Date() + " hello");
    }
}

package schedule;

import java.util.Date;
import java.util.concurrent.ScheduledFuture;

import javax.annotation.PostConstruct;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.scheduling.Trigger;
import org.springframework.scheduling.TriggerContext;
import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
import org.springframework.scheduling.support.CronTrigger;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
@SpringBootApplication
public class ScheduleApplication {

    @Autowired
    private ThreadPoolTaskScheduler threadPoolTaskScheduler;

    @Bean
    public ThreadPoolTaskScheduler threadPoolTaskScheduler(){
        return new ThreadPoolTaskScheduler();
    }

    private ScheduledFuture future;

    @RequestMapping("/")
    @ResponseBody
    public String home(){
        return "home";
    }

    ///方法一

    @RequestMapping("/startCron")
    @ResponseBody
    public String startCron(){
        System.out.println("x0");
        //threadPoolTaskScheduler.shutdown();
        future = threadPoolTaskScheduler.schedule(new Say(), new CronTrigger("*/5 * * * * *"));
        System.out.println("x1");
        return "x";
    }

    @RequestMapping("/stopCron")
    @ResponseBody
    public String stopCron(){
        System.out.println("stop >>>>>");
        if(future != null) {
            future.cancel(true);
        }
        //future = threadPoolTaskScheduler.schedule(new Say(), new CronTrigger("*/5 * * * * *"));
        System.out.println("stop <<<<<");
        return "stop cron";
    }

    @RequestMapping("/startCron10")
    @ResponseBody
    public String startCron10(){
        System.out.println("x100");
        future = threadPoolTaskScheduler.schedule(new Say10(), new CronTrigger("*/12 * * * * *"));
        System.out.println("x101");
        return "x10";
    }


    ///方法二

    private String cronStr = "*/5 * * * * *";
    @RequestMapping("/startCron1")
    @ResponseBody
    public String startCron1(){
        System.out.println("startCron1 >>>>");
        threadPoolTaskScheduler.schedule(new Say(), new Trigger(){
            @Override
            public Date nextExecutionTime(TriggerContext triggerContext){
                return new CronTrigger(cronStr).nextExecutionTime(triggerContext);
            }
        });
        System.out.println("startCron1 <<<<");
        return "*****";
    }


    @PostConstruct
    public void start(){
        startCron1();
    }

    @RequestMapping("/changeCronStr")
    @ResponseBody
    public String changeCronStr(){
        cronStr = "*/12 * * * * *";
        System.out.println("change "  + cronStr);
        return  cronStr;
    }

    @RequestMapping("/changeCronStr5")
    @ResponseBody
    public String changeCronStr5(){
        cronStr = "*/5 * * * * *";
        System.out.println("change "  + cronStr);
        return  cronStr;
    }


    public static void main(String[] args) {
        SpringApplication.run(ScheduleApplication.class, args);
    }
}

说明 threadPoolTaskScheduler.shutdown();会抛出异常
@PostConstruct 在依赖注入完成后，进行调用
使用

{
    sartcron();
}

会产生空指针异常，以为依赖注入为完成.
@PostConstruct还可以使用BeanPostProcessor的功能来完成.
或使用

public class StartupListener implements ApplicationListener<ContextRefreshedEvent>

监听事件.

参考
Spring/SpringMVC在启动完成后执行方法
http://blog.csdn.net/renyisheng/article/details/50803875
Spring/SpringMVC在启动完成后执行方法
http://www.cnblogs.com/itjcw/p/5977911.html
Spring @Scheduled定时任务动态修改cron参数
http://blog.csdn.net/xht555/article/details/53121962
Java 定时任务系列（2）-Spring 定时任务的几种实现
https://segmentfault.com/a/1190000002504252
java timer task schedule
http://stackoverflow.com/questions/4044729/java-timer-task-schedule
[Spring笔记]支持注解的Spring调度器
http://www.w2bc.com/article/169011