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

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