SpringBoot如何配置和使用Schedule

這篇文章主要講解了SpringBoot如何配置和使用Schedule，內容清晰明了，對此有興趣的小伙伴可以學習一下，相信大家閱讀完之后會有幫助。

我們在平常項目開發中，經常會用到周期性定時任務，這個時候使用定時任務就能很方便的實現。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，所以無需引入其他依賴。

2、啟用定時任務

在啟動類或者配置類上增加@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、添加定時任務

Schdule支持cron表達式、固定間隔時間、固定頻率三種調度方式。

1）cron表達式定時任務

與Linux下定時任務用到的Cron表達式一樣。

@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表達式方式配置的定時任務如果其執行時間超過調度頻率時，調度器會在下個執行周期執行。如第一次執行從第0秒開始，執行時長3秒，則下次執行為第4秒。

2）固定間隔定時任務

下一次的任務執行時間是從上一次定時任務結束時間開始計算。

@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）固定頻率定時任務

按照指定頻率執行任務

@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：當方法的執行時間超過任務調度頻率時，調度器會在當前方法執行完成后立即執行下次任務。

二、配置多個定時任務并發執行

1、并行or串行？

缺省狀態下，當我們沒有給定時任務配置線程池時，Schedule是串行執行，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

可以看出來只有一個線程穿行執行所有定時任務。

2、Schedule并行執行配置

定時調度的并行化，有兩種配置方式：

1）修改任務調度器默認使用的線程池：添加一個configuration，實現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）直接將任務交給一步線程池處理：啟用@EnableAsync注解，并在每一個定時任務方法上使用@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這種方式對于每一次定時任務的執行都會創建新的線程，這樣對內存資源是一種浪費，嚴重情況下還會導致服務掛掉，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

看完上述內容，是不是對SpringBoot如何配置和使用Schedule有進一步的了解，如果還想學習更多內容，歡迎關注億速云行業資訊頻道。