我們?cè)谄匠ｍ?xiàng)目開(kāi)發(fā)中，經(jīng)常會(huì)用到周期性定時(shí)任務(wù)，這個(gè)時(shí)候使用定時(shí)任務(wù)就能很方便的實(shí)現(xiàn)。在SpringBoot中用得最多的就是Schedule。

一、SpringBoot集成Schedule

1、依賴配置

由于Schedule就包含在spring-boot-starter中，所以無(wú)需引入其他依賴。

2、啟用定時(shí)任務(wù)

在啟動(dòng)類(lèi)或者配置類(lèi)上增加@EnableScheduling注解。

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.scheduling.annotation.EnableScheduling;

@EnableScheduling
@SpringBootApplication
public class DemoApplication {

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

3、添加定時(shí)任務(wù)

Schdule支持cron表達(dá)式、固定間隔時(shí)間、固定頻率三種調(diào)度方式。

1）cron表達(dá)式定時(shí)任務(wù)

與Linux下定時(shí)任務(wù)用到的Cron表達(dá)式一樣。

@Component
@EnableScheduling
public class MyCronTask {

  private static final Logger logger = LoggerFactory.getLogger(MyCronTask.class); 

  @Scheduled(cron = "0/1 * * * * *")
  void cronSchedule(){
    logger.info("cron schedule execute");
  }

}

PS：Cron表達(dá)式方式配置的定時(shí)任務(wù)如果其執(zhí)行時(shí)間超過(guò)調(diào)度頻率時(shí)，調(diào)度器會(huì)在下個(gè)執(zhí)行周期執(zhí)行。如第一次執(zhí)行從第0秒開(kāi)始，執(zhí)行時(shí)長(zhǎng)3秒，則下次執(zhí)行為第4秒。

2）固定間隔定時(shí)任務(wù)

下一次的任務(wù)執(zhí)行時(shí)間是從上一次定時(shí)任務(wù)結(jié)束時(shí)間開(kāi)始計(jì)算。

@Scheduled(fixedDelay = 2)
void fixedDelaySchedule() throws Exception{
  Thread.sleep(2000);
  logger.info("fixed delay schedule execute");
}

輸出：

2020-04-23 23:11:54.362 INFO 85325 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : fixed delay schedule execute
2020-04-23 23:11:58.365 INFO 85325 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : fixed delay schedule execute
2020-04-23 23:12:02.372 INFO 85325 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : fixed delay schedule execute
2020-04-23 23:12:06.381 INFO 85325 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : fixed delay schedule execute

3）固定頻率定時(shí)任務(wù)

按照指定頻率執(zhí)行任務(wù)

@Scheduled(fixedRate = 2000)
void fixedRateSchedule() throws Exception{
  Thread.sleep(3000);
  logger.info("fixed rate schedule execute");
}

輸出：

2020-04-23 23:16:14.750 INFO 85328 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : fixed rate schedule execute
2020-04-23 23:16:17.754 INFO 85328 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : fixed rate schedule execute
2020-04-23 23:16:20.760 INFO 85328 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : fixed rate schedule execute
2020-04-23 23:16:23.760 INFO 85328 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : fixed rate schedule execute
2020-04-23 23:16:26.764 INFO 85328 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : fixed rate schedule execute

PS：當(dāng)方法的執(zhí)行時(shí)間超過(guò)任務(wù)調(diào)度頻率時(shí)，調(diào)度器會(huì)在當(dāng)前方法執(zhí)行完成后立即執(zhí)行下次任務(wù)。

二、配置多個(gè)定時(shí)任務(wù)并發(fā)執(zhí)行

1、并行or串行？

缺省狀態(tài)下，當(dāng)我們沒(méi)有給定時(shí)任務(wù)配置線程池時(shí)，Schedule是串行執(zhí)行，如下：

@Component
@EnableScheduling
public class MyCronTask {

  private static final Logger logger = LoggerFactory.getLogger(MyCronTask.class);
  
  @Scheduled(fixedDelay = 2000)
  void task1Schedule() throws Exception{
    Thread.sleep(2000);
    logger.info("task1 execute");
  }

  @Scheduled(fixedDelay = 2000)
  void task2Schedule() throws Exception{
    Thread.sleep(2000);
    logger.info("task2 execute");
  }

  @Scheduled(fixedDelay = 2000)
  void task3Schedule() throws Exception{
    Thread.sleep(2000);
    logger.info("task3 execute");
  }
}

輸出：

2020-04-23 23:19:46.970 INFO 85332 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : task1 execute
2020-04-23 23:19:48.973 INFO 85332 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : task2 execute
2020-04-23 23:19:50.974 INFO 85332 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : task3 execute
2020-04-23 23:19:52.978 INFO 85332 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : task1 execute
2020-04-23 23:19:54.984 INFO 85332 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : task2 execute
2020-04-23 23:19:56.984 INFO 85332 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : task3 execute

可以看出來(lái)只有一個(gè)線程穿行執(zhí)行所有定時(shí)任務(wù)。

2、Schedule并行執(zhí)行配置

定時(shí)調(diào)度的并行化，有兩種配置方式：

1）修改任務(wù)調(diào)度器默認(rèn)使用的線程池：添加一個(gè)configuration，實(shí)現(xiàn)SchedulingConfigurer接口就可以了。

@Configuration
public class ScheduleConfig implements SchedulingConfigurer{

  @Override
  public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
    taskRegistrar.setTaskScheduler(getTaskScheduler());
  }

  @Bean
  public TaskScheduler getTaskScheduler() {
    ThreadPoolTaskScheduler taskScheduler = new ThreadPoolTaskScheduler();
    taskScheduler.setPoolSize(3);
    taskScheduler.setThreadNamePrefix("myworker-");
    taskScheduler.setWaitForTasksToCompleteOnShutdown(true);
    return taskScheduler;
  }
}

再次執(zhí)行后，輸出：

2020-04-23 23:33:14.197 INFO 85461 --- [ myworker-2] com.springboot.study.tasks.MyCronTask : task2 execute
2020-04-23 23:33:14.197 INFO 85461 --- [ myworker-1] com.springboot.study.tasks.MyCronTask : task1 execute
2020-04-23 23:33:14.197 INFO 85461 --- [ myworker-3] com.springboot.study.tasks.MyCronTask : task3 execute
2020-04-23 23:33:18.203 INFO 85461 --- [ myworker-2] com.springboot.study.tasks.MyCronTask : task2 execute
2020-04-23 23:33:18.203 INFO 85461 --- [ myworker-3] com.springboot.study.tasks.MyCronTask : task1 execute
2020-04-23 23:33:18.204 INFO 85461 --- [ myworker-1] com.springboot.study.tasks.MyCronTask : task3 execute
2020-04-23 23:33:22.208 INFO 85461 --- [ myworker-1] com.springboot.study.tasks.MyCronTask : task3 execute
2020-04-23 23:33:22.208 INFO 85461 --- [ myworker-2] com.springboot.study.tasks.MyCronTask : task2 execute
2020-04-23 23:33:22.208 INFO 85461 --- [ myworker-3] com.springboot.study.tasks.MyCronTask : task1 execute

2）直接將任務(wù)交給一步線程池處理：?jiǎn)⒂聾EnableAsync注解，并在每一個(gè)定時(shí)任務(wù)方法上使用@Async注解。

@Component
@EnableScheduling
@EnableAsync
@Async
public class MyCronTask {

  private static final Logger logger = LoggerFactory.getLogger(MyCronTask.class);

  @Scheduled(fixedDelay = 2000)
  void task1Schedule() throws Exception{
    Thread.sleep(2000);
    logger.info("task1 execute");
  }

  @Scheduled(fixedDelay = 2000)
  void task2Schedule() throws Exception{
    Thread.sleep(2000);
    logger.info("task2 execute");
  }

  @Scheduled(fixedDelay = 2000)
  void task3Schedule() throws Exception{
    Thread.sleep(2000);
    logger.info("task3 execute");
  }
}

輸出如下：

2020-04-23 23:38:00.614 INFO 85468 --- [ task-1] com.springboot.study.tasks.MyCronTask : task1 execute
2020-04-23 23:38:00.614 INFO 85468 --- [ task-3] com.springboot.study.tasks.MyCronTask : task3 execute
2020-04-23 23:38:00.614 INFO 85468 --- [ task-2] com.springboot.study.tasks.MyCronTask : task2 execute
2020-04-23 23:38:02.620 INFO 85468 --- [ task-4] com.springboot.study.tasks.MyCronTask : task1 execute
2020-04-23 23:38:02.620 INFO 85468 --- [ task-5] com.springboot.study.tasks.MyCronTask : task2 execute
2020-04-23 23:38:02.620 INFO 85468 --- [ task-6] com.springboot.study.tasks.MyCronTask : task3 execute

有上面輸出可以看出來(lái)這種方式對(duì)于每一次定時(shí)任務(wù)的執(zhí)行都會(huì)創(chuàng)建新的線程，這樣對(duì)內(nèi)存資源是一種浪費(fèi)，嚴(yán)重情況下還會(huì)導(dǎo)致服務(wù)掛掉，因此為了更好控制線程的使用，我們可以自定義線程池。

首先配置線程池：

@Configuration
public class MyTaskExecutor {

  @Bean(name = "myExecutor")
  public TaskExecutor getMyExecutor() {
    ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
    taskExecutor.setCorePoolSize(3);
    taskExecutor.setMaxPoolSize(10);
    taskExecutor.setQueueCapacity(20);
    taskExecutor.setThreadNamePrefix("myExecutor-");
    taskExecutor.initialize();
    return taskExecutor;
  }
}

使用我們自己的線程池：

@Component
@EnableScheduling
@EnableAsync
@Async("myExecutor")
public class MyCronTask {

  private static final Logger logger = LoggerFactory.getLogger(MyCronTask.class);

  @Scheduled(fixedDelay = 2000)
  void task1Schedule() throws Exception{
    Thread.sleep(2000);
    logger.info("task1 execute");
  }

  @Scheduled(fixedDelay = 2000)
  void task2Schedule() throws Exception{
    Thread.sleep(2000);
    logger.info("task2 execute");
  }

  @Scheduled(fixedDelay = 2000)
  void task3Schedule() throws Exception{
    Thread.sleep(2000);
    logger.info("task3 execute");
  }
}

輸出：

2020-04-23 23:46:47.404 INFO 85488 --- [ myExecutor-1] com.springboot.study.tasks.MyCronTask : task1 execute
2020-04-23 23:46:47.404 INFO 85488 --- [ myExecutor-3] com.springboot.study.tasks.MyCronTask : task3 execute
2020-04-23 23:46:47.404 INFO 85488 --- [ myExecutor-2] com.springboot.study.tasks.MyCronTask : task2 execute
2020-04-23 23:46:49.404 INFO 85488 --- [ myExecutor-3] com.springboot.study.tasks.MyCronTask : task2 execute
2020-04-23 23:46:49.404 INFO 85488 --- [ myExecutor-2] com.springboot.study.tasks.MyCronTask : task3 execute
2020-04-23 23:46:49.404 INFO 85488 --- [ myExecutor-1] com.springboot.study.tasks.MyCronTask : task1 execute
2020-04-23 23:46:51.405 INFO 85488 --- [ myExecutor-2] com.springboot.study.tasks.MyCronTask : task2 execute
2020-04-23 23:46:51.405 INFO 85488 --- [ myExecutor-3] com.springboot.study.tasks.MyCronTask : task1 execute
2020-04-23 23:46:51.405 INFO 85488 --- [ myExecutor-1] com.springboot.study.tasks.MyCronTask : task3 execute

以上就是本文的全部?jī)?nèi)容，希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。

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