SpringBoot定时任务@Scheduled注解详解 Bertha 。 2024-03-26 20:56 33阅读 0赞 ### SpringBoot定时任务@Scheduled注解详解 ### ### SpringBoot定时任务@Scheduled注解详解 ### * 项目开发中,经常会遇到定时任务的场景,Spring提供了`@Scheduled注解`,方便进行定时任务的开发 ### 概述 ### * 要使用`@Scheduled`注解,首先需要在启动类添加`@EnableScheduling`,启用Spring的计划任务执行功能,这样可以在容器中的任何Spring管理的bean上检测`@Scheduled`注解,执行计划任务 ### 注解定义 ### * @Target({ElementType.METHOD, ElementType.ANNOTATION_TYPE}) @Retention(RetentionPolicy.RUNTIME) @Documented @Repeatable(Schedules.class) public @interface Scheduled { String cron() default ""; String zone() default ""; long fixedDelay() default -1; String fixedDelayString() default ""; long fixedRate() default -1; String fixedRateString() default ""; long initialDelay() default -1; String initialDelayString() default ""; } ### 参数说明 ### * ![5b9a2948163346689e69794e4fd44989.png][] ### 源码解析 ### * 配置了`@Scheduled`注解的方法,Spring的处理是通过注册ScheduledAnnotationBeanPostProcessor来执行,将不同配置参数的任务分配给不同的handler处理,核心代码如下 * org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor\#postProcessAfterInitialization * @Override public Object postProcessAfterInitialization(Object bean, String beanName) { if (bean instanceof AopInfrastructureBean || bean instanceof TaskScheduler || bean instanceof ScheduledExecutorService) { // Ignore AOP infrastructure such as scoped proxies. return bean; } Class<?> targetClass = AopProxyUtils.ultimateTargetClass(bean); if (!this.nonAnnotatedClasses.contains(targetClass) && AnnotationUtils.isCandidateClass(targetClass, Arrays.asList(Scheduled.class, Schedules.class))) { Map<Method, Set<Scheduled>> annotatedMethods = MethodIntrospector.selectMethods(targetClass, (MethodIntrospector.MetadataLookup<Set<Scheduled>>) method -> { Set<Scheduled> scheduledMethods = AnnotatedElementUtils.getMergedRepeatableAnnotations( method, Scheduled.class, Schedules.class); return (!scheduledMethods.isEmpty() ? scheduledMethods : null); }); if (annotatedMethods.isEmpty()) { this.nonAnnotatedClasses.add(targetClass); if (logger.isTraceEnabled()) { logger.trace("No @Scheduled annotations found on bean class: " + targetClass); } } else { // Non-empty set of methods annotatedMethods.forEach((method, scheduledMethods) -> scheduledMethods.forEach(scheduled -> processScheduled(scheduled, method, bean))); if (logger.isTraceEnabled()) { logger.trace(annotatedMethods.size() + " @Scheduled methods processed on bean '" + beanName + "': " + annotatedMethods); } } } return bean; } * org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor\#processScheduled * /** * Process the given {@code @Scheduled} method declaration on the given bean. * @param scheduled the @Scheduled annotation * @param method the method that the annotation has been declared on * @param bean the target bean instance * @see #createRunnable(Object, Method) */ protected void processScheduled(Scheduled scheduled, Method method, Object bean) { try { Runnable runnable = createRunnable(bean, method); boolean processedSchedule = false; String errorMessage = "Exactly one of the 'cron', 'fixedDelay(String)', or 'fixedRate(String)' attributes is required"; Set<ScheduledTask> tasks = new LinkedHashSet<>(4); // Determine initial delay long initialDelay = scheduled.initialDelay(); String initialDelayString = scheduled.initialDelayString(); if (StringUtils.hasText(initialDelayString)) { Assert.isTrue(initialDelay < 0, "Specify 'initialDelay' or 'initialDelayString', not both"); if (this.embeddedValueResolver != null) { initialDelayString = this.embeddedValueResolver.resolveStringValue(initialDelayString); } if (StringUtils.hasLength(initialDelayString)) { try { initialDelay = parseDelayAsLong(initialDelayString); } catch (RuntimeException ex) { throw new IllegalArgumentException( "Invalid initialDelayString value \"" + initialDelayString + "\" - cannot parse into long"); } } } // Check cron expression String cron = scheduled.cron(); if (StringUtils.hasText(cron)) { String zone = scheduled.zone(); if (this.embeddedValueResolver != null) { cron = this.embeddedValueResolver.resolveStringValue(cron); zone = this.embeddedValueResolver.resolveStringValue(zone); } if (StringUtils.hasLength(cron)) { Assert.isTrue(initialDelay == -1, "'initialDelay' not supported for cron triggers"); processedSchedule = true; if (!Scheduled.CRON_DISABLED.equals(cron)) { TimeZone timeZone; if (StringUtils.hasText(zone)) { timeZone = StringUtils.parseTimeZoneString(zone); } else { timeZone = TimeZone.getDefault(); } tasks.add(this.registrar.scheduleCronTask(new CronTask(runnable, new CronTrigger(cron, timeZone)))); } } } // At this point we don't need to differentiate between initial delay set or not anymore if (initialDelay < 0) { initialDelay = 0; } // Check fixed delay long fixedDelay = scheduled.fixedDelay(); if (fixedDelay >= 0) { Assert.isTrue(!processedSchedule, errorMessage); processedSchedule = true; tasks.add(this.registrar.scheduleFixedDelayTask(new FixedDelayTask(runnable, fixedDelay, initialDelay))); } String fixedDelayString = scheduled.fixedDelayString(); if (StringUtils.hasText(fixedDelayString)) { if (this.embeddedValueResolver != null) { fixedDelayString = this.embeddedValueResolver.resolveStringValue(fixedDelayString); } if (StringUtils.hasLength(fixedDelayString)) { Assert.isTrue(!processedSchedule, errorMessage); processedSchedule = true; try { fixedDelay = parseDelayAsLong(fixedDelayString); } catch (RuntimeException ex) { throw new IllegalArgumentException( "Invalid fixedDelayString value \"" + fixedDelayString + "\" - cannot parse into long"); } tasks.add(this.registrar.scheduleFixedDelayTask(new FixedDelayTask(runnable, fixedDelay, initialDelay))); } } // Check fixed rate long fixedRate = scheduled.fixedRate(); if (fixedRate >= 0) { Assert.isTrue(!processedSchedule, errorMessage); processedSchedule = true; tasks.add(this.registrar.scheduleFixedRateTask(new FixedRateTask(runnable, fixedRate, initialDelay))); } String fixedRateString = scheduled.fixedRateString(); if (StringUtils.hasText(fixedRateString)) { if (this.embeddedValueResolver != null) { fixedRateString = this.embeddedValueResolver.resolveStringValue(fixedRateString); } if (StringUtils.hasLength(fixedRateString)) { Assert.isTrue(!processedSchedule, errorMessage); processedSchedule = true; try { fixedRate = parseDelayAsLong(fixedRateString); } catch (RuntimeException ex) { throw new IllegalArgumentException( "Invalid fixedRateString value \"" + fixedRateString + "\" - cannot parse into long"); } tasks.add(this.registrar.scheduleFixedRateTask(new FixedRateTask(runnable, fixedRate, initialDelay))); } } // Check whether we had any attribute set Assert.isTrue(processedSchedule, errorMessage); // Finally register the scheduled tasks synchronized (this.scheduledTasks) { Set<ScheduledTask> regTasks = this.scheduledTasks.computeIfAbsent(bean, key -> new LinkedHashSet<>(4)); regTasks.addAll(tasks); } } catch (IllegalArgumentException ex) { throw new IllegalStateException( "Encountered invalid @Scheduled method '" + method.getName() + "': " + ex.getMessage()); } } * org.springframework.scheduling.config.ScheduledTaskRegistrar\#scheduleTasks * /** * Schedule all registered tasks against the underlying * {@linkplain #setTaskScheduler(TaskScheduler) task scheduler}. */ proected void scheduleTasks() { if (this.taskScheduler == null) { this.localExecutor = Executors.newSingleThreadScheduledExecutor(); this.taskScheduler = new ConcurrentTaskScheduler(this.localExecutor); } if (this.triggerTasks != null) { for (TriggerTask task : this.triggerTasks) { addScheduledTask(scheduleTriggerTask(task)); } } if (this.cronTasks != null) { for (CronTask task : this.cronTasks) { addScheduledTask(scheduleCronTask(task)); } } if (this.fixedRateTasks != null) { for (IntervalTask task : this.fixedRateTasks) { addScheduledTask(scheduleFixedRateTask(task)); } } if (this.fixedDelayTasks != null) { for (IntervalTask task : this.fixedDelayTasks) { addScheduledTask(scheduleFixedDelayTask(task)); } } } ### 使用详解 ### #### 定时任务同步/异步执行 #### * 定时任务执行默认是单线程模式,会创建一个本地线程池,线程池大小为1。当项目中有多个定时任务时,任务之间会相互等待,同步执行 * 源码: * // org.springframework.scheduling.config.ScheduledTaskRegistrar#scheduleTasks if (this.taskScheduler == null) { this.localExecutor = Executors.newSingleThreadScheduledExecutor(); this.taskScheduler = new ConcurrentTaskScheduler(this.localExecutor); } // java.util.concurrent.Executors#newSingleThreadScheduledExecutor() public static ScheduledExecutorService newSingleThreadScheduledExecutor() { return new DelegatedScheduledExecutorService (new ScheduledThreadPoolExecutor(1)); } * 代码示例: * @Slf4j @Component public class RunIntervalTestScheduler { @Scheduled(cron = "0/1 * * * * ?") public void singleThreadTest1() { log.info("singleThreadTest1"); LockSupport.parkNanos(TimeUnit.SECONDS.toNanos(1)); } @Scheduled(cron = "0/1 * * * * ?") public void singleThreadTest2() { log.info("singleThreadTest2"); LockSupport.parkNanos(TimeUnit.SECONDS.toNanos(1)); } @Scheduled(cron = "0/1 * * * * ?") public void singleThreadTest3() { log.info("singleThreadTest3"); LockSupport.parkNanos(TimeUnit.SECONDS.toNanos(1)); } } * 执行结果: * ![40d4d56996e24ec6a6552dc0bfc6f4fc.png][] * 可以看到,默认情况下,三个任务串行执行,都使用`pool-1-thread-1`同一个线程池,并且线程只有一个 * 可以通过实现`SchedulingConfigurer`接口,手动创建线程池,配置期望的线程数量 * 示例代码: * @Configuration public class ScheduledConfig implements SchedulingConfigurer { /** * 任务执行线程池大小 */ private static final int TASK_POOL_SIZE = 50; /** * 线程名 */ private static final String TASK_THREAD_PREFIX = "test-task-"; @Override public void configureTasks(ScheduledTaskRegistrar scheduledTaskRegistrar) { ThreadPoolTaskScheduler taskPool = new ThreadPoolTaskScheduler(); taskPool.setPoolSize(TASK_POOL_SIZE); taskPool.setThreadNamePrefix(TASK_THREAD_PREFIX); taskPool.initialize(); scheduledTaskRegistrar.setTaskScheduler(taskPool); } } * 任务执行结果: * ![58472fe68140441d8e5e858b187fbf55.png][] * 此时任务的执行已经异步化,从自定义线程池中分配线程执行任务,在实际应用中需要考虑实际任务数量,创建相应大小的线程池 #### fixedRate/fixedDelay区别 #### * fixedRate是配置上一次任务执行开始到下一次执行开始的间隔时间,不会等待上一次任务执行完成就会调度下一次任务,将其放入等待队列中 * 代码示例: * @Slf4j @Component public class RunIntervalTestScheduler { @Scheduled(initialDelay = 1000, fixedRate = 1000) public void fixedRate() throws Exception { log.info("fixedRate run"); TimeUnit.SECONDS.sleep(3); } } * 执行结果: * ![4214d91b66d143fbba86ac3dd7001d80.png][] * 任务配置的fixedRate为1s,执行日志打印的时间间隔都是3s左右,也就是上一次执行完成后,紧接着就执行下一次任务 * fixedDelay是配置的上一次任务执行结束到下一次执行开始的间隔时间,也就是说会等待上一次任务执行结束后,延迟间隔时间,再执行下一次任务 * 代码示例: * @Slf4j @Component public class RunIntervalTestScheduler { @Scheduled(initialDelay = 1000, fixedDelay = 1000) public void fixedDelay() throws Exception { log.info("fixedDelay run"); TimeUnit.SECONDS.sleep(3); } } * 执行结果: * ![1b7b1f27d88b4c928a08992ea040bfe7.png][] * 任务配置的fixedDelay为1s,执行日志打印的时间间隔都是4s左右,也就是上一次执行完成后,延迟1s后执行下一次任务 * cron表达式如果配置为类似每秒执行、每分钟执行(例:0/1 \* \* \* \* ?, 每秒执行),调度跟fixedDelay是一致的,也是在上一次任务执行结束后,等待间隔时间 * 代码示例: * @Slf4j @Component public class RunIntervalTestScheduler { @Scheduled(cron = "0/1 * * * * ?") public void cronRun() throws Exception{ log.info("cron run"); TimeUnit.SECONDS.sleep(3); } } * 执行结果: * ![d3b0e219c1e84a41b0c1f6191346b602.png][] * 执行日志打印的时间间隔都是4s左右,也就是上一次执行完成后,延迟1s后执行下一次任务 * cron表达式如果配置为固定时间执行(例:1 \* \* \* \* ?, 秒数为1时执行),若上一次任务没有执行完,则不会调度本次任务,跳过本次执行,等待下一次执行周期 * 代码示例: * @Slf4j @Component public class RunIntervalTestScheduler { @Scheduled(cron = "1 * * * * ?") public void cronRun() throws Exception{ log.info("cron run"); TimeUnit.SECONDS.sleep(70); } } * 执行结果: * ![8d793ad5a5e5485e8ff948e3eb48f28b.png][] * 上一次任务未执行完毕,则跳过了本次执行 [5b9a2948163346689e69794e4fd44989.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/25/47c1453268424ef8a671366b89714569.png [40d4d56996e24ec6a6552dc0bfc6f4fc.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/25/73d2eee23aba40e69a37d1de0969cecd.png [58472fe68140441d8e5e858b187fbf55.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/25/9f80e9dc9e20459c948fbebe22a38baf.png [4214d91b66d143fbba86ac3dd7001d80.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/25/87ce56ce76374b8fbc795758bf25364e.png [1b7b1f27d88b4c928a08992ea040bfe7.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/25/522da3d41822407ba766677ed960b45f.png [d3b0e219c1e84a41b0c1f6191346b602.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/25/a52fa7a97ae3463482c82d5af187c433.png [8d793ad5a5e5485e8ff948e3eb48f28b.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/25/9163a4e8f6144491ba4b783daced4c14.png
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