Spring调度框架EnableScheduling&Scheduled源码解析
作者:mumubili
前言
在实际项目开发中,有时会遇到定时调度的开发需要,这部分的功能在Spring框架中给出了较好的支持,即@EnableScheduling&Scheduled定时调度框架,本着不仅知其然还要知其所以然的指导思想,下面对该调度框架进行源码解析,以便更好的理解其执行过程;
1.开启调度框架
Spring框架中,为了开启调度框架功能,需要在配置类上标注@EnableScheduling注解,这也是Spring中Enable*模式的典型应用,下面看一下@EnableScheduling的具体实现:
@Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Import(SchedulingConfiguration.class) @Documented public @interface EnableScheduling { }
这里通过@Import注解,导入了配置类SchedulingConfiguration,进一步看下SchedulingConfiguration配置类的源码,如下:
@Configuration(proxyBeanMethods = false) @Role(BeanDefinition.ROLE_INFRASTRUCTURE) public class SchedulingConfiguration { @Bean(name = TaskManagementConfigUtils.SCHEDULED_ANNOTATION_PROCESSOR_BEAN_NAME) @Role(BeanDefinition.ROLE_INFRASTRUCTURE) public ScheduledAnnotationBeanPostProcessor scheduledAnnotationProcessor() { return new ScheduledAnnotationBeanPostProcessor(); } }
可以看到,这里定义了一个Bean后处理器ScheduledAnnotationBeanPostProcessor,调度框架的解析逻辑也是定义在ScheduledAnnotationBeanPostProcessor中的,下面着重对该部分进行具体分析;
2.ScheduledAnnotationBeanPostProcessor Bean后处理器分析
Bean后处理器中,主要分析下后处理器的拦截方法,如下:
@Override public Object postProcessBeforeInitialization(Object bean, String beanName) { return bean; } @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> scheduledAnnotations = AnnotatedElementUtils.getMergedRepeatableAnnotations( method, Scheduled.class, Schedules.class); return (!scheduledAnnotations.isEmpty() ? scheduledAnnotations : 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, scheduledAnnotations) -> scheduledAnnotations.forEach(scheduled -> processScheduled(scheduled, method, bean))); if (logger.isTraceEnabled()) { logger.trace(annotatedMethods.size() + " @Scheduled methods processed on bean '" + beanName + "': " + annotatedMethods); } } } return bean; }
如上,postProcessAfterInitialization方法中,主要对标注@Scheduled和聚合注解@Schedules的类成员方法进行处理,主要分为2步:
1)识别标注@Scheduled和聚合注解@Schedules的方法;
2)对注解方法调用processScheduled方法进行处理;
方法processScheduled处理过程如下:
/** * Process the given {@code @Scheduled} method declaration on the given bean. * @param scheduled the {@code @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 = convertToMillis(scheduled.initialDelay(), scheduled.timeUnit()); 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 = convertToMillis(initialDelayString, scheduled.timeUnit()); } 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 = convertToMillis(scheduled.fixedDelay(), scheduled.timeUnit()); 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 = convertToMillis(fixedDelayString, scheduled.timeUnit()); } 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 = convertToMillis(scheduled.fixedRate(), scheduled.timeUnit()); 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 = convertToMillis(fixedRateString, scheduled.timeUnit()); } 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()); } }
上述处理过程主要包含以下几步:
1)将调用目标方法的过程包装为ScheduledMethodRunnable类
2)构造CronTask并进行调度
3)构造FixedDelayTask并进行调度
4)构造FixedRateTask并进行调度
下面主要说明下调度任务的类型以及具体的调度方法;
2.1 调度框架支持的Task类型
Spring调度框架中重要支持3种调度任务类型(继承结构如上图),具体说明如下:
1)CronTask:cron表达式调度的任务
2)FixedDelayTask:固定延迟时间执行的任务
3)FixedRateTask:固定速率执行的任务
2.2 对Task进行调度执行
上述3种的调度执行实现近似,下面以FixedDelayTask进行说明,该任务的调度方法为scheduleFixedDelayTask,具体实现如下:
/** * Schedule the specified fixed-delay task, either right away if possible * or on initialization of the scheduler. * @return a handle to the scheduled task, allowing to cancel it * (or {@code null} if processing a previously registered task) * @since 5.0.2 */ @Nullable public ScheduledTask scheduleFixedDelayTask(FixedDelayTask task) { ScheduledTask scheduledTask = this.unresolvedTasks.remove(task); boolean newTask = false; if (scheduledTask == null) { scheduledTask = new ScheduledTask(task); newTask = true; } if (this.taskScheduler != null) { if (task.getInitialDelay() > 0) { Date startTime = new Date(this.taskScheduler.getClock().millis() + task.getInitialDelay()); scheduledTask.future = this.taskScheduler.scheduleWithFixedDelay(task.getRunnable(), startTime, task.getInterval()); } else { scheduledTask.future = this.taskScheduler.scheduleWithFixedDelay(task.getRunnable(), task.getInterval()); } } else { addFixedDelayTask(task); this.unresolvedTasks.put(task, scheduledTask); } return (newTask ? scheduledTask : null); }
这里主要包含以下几步:
1)将调度任务包装为ScheduledTask类型,其中封装了执行结果ScheduledFuture
2)存在任务调度器(taskScheduler)时,直接进行调度执行
3)不存在任务调度器(taskScheduler)时,将任务暂存到fixedDelayTasks中,待调用afterPropertiesSet方法时再进行调度执行
3.任务调度器
3.1 任务调度器获取
任务调度器支持自定义,当无自定义调度器时,调度框架提供了默认的任务调度器;
自定义任务调度器的处理逻辑在方法finishRegistration中,如下:
private void finishRegistration() { if (this.scheduler != null) { this.registrar.setScheduler(this.scheduler); } if (this.beanFactory instanceof ListableBeanFactory) { Map<String, SchedulingConfigurer> beans = ((ListableBeanFactory) this.beanFactory).getBeansOfType(SchedulingConfigurer.class); List<SchedulingConfigurer> configurers = new ArrayList<>(beans.values()); AnnotationAwareOrderComparator.sort(configurers); for (SchedulingConfigurer configurer : configurers) { configurer.configureTasks(this.registrar); } } if (this.registrar.hasTasks() && this.registrar.getScheduler() == null) { Assert.state(this.beanFactory != null, "BeanFactory must be set to find scheduler by type"); try { // Search for TaskScheduler bean... this.registrar.setTaskScheduler(resolveSchedulerBean(this.beanFactory, TaskScheduler.class, false)); } catch (NoUniqueBeanDefinitionException ex) { if (logger.isTraceEnabled()) { logger.trace("Could not find unique TaskScheduler bean - attempting to resolve by name: " + ex.getMessage()); } try { this.registrar.setTaskScheduler(resolveSchedulerBean(this.beanFactory, TaskScheduler.class, true)); } catch (NoSuchBeanDefinitionException ex2) { if (logger.isInfoEnabled()) { logger.info("More than one TaskScheduler bean exists within the context, and " + "none is named 'taskScheduler'. Mark one of them as primary or name it 'taskScheduler' " + "(possibly as an alias); or implement the SchedulingConfigurer interface and call " + "ScheduledTaskRegistrar#setScheduler explicitly within the configureTasks() callback: " + ex.getBeanNamesFound()); } } } catch (NoSuchBeanDefinitionException ex) { if (logger.isTraceEnabled()) { logger.trace("Could not find default TaskScheduler bean - attempting to find ScheduledExecutorService: " + ex.getMessage()); } // Search for ScheduledExecutorService bean next... try { this.registrar.setScheduler(resolveSchedulerBean(this.beanFactory, ScheduledExecutorService.class, false)); } catch (NoUniqueBeanDefinitionException ex2) { if (logger.isTraceEnabled()) { logger.trace("Could not find unique ScheduledExecutorService bean - attempting to resolve by name: " + ex2.getMessage()); } try { this.registrar.setScheduler(resolveSchedulerBean(this.beanFactory, ScheduledExecutorService.class, true)); } catch (NoSuchBeanDefinitionException ex3) { if (logger.isInfoEnabled()) { logger.info("More than one ScheduledExecutorService bean exists within the context, and " + "none is named 'taskScheduler'. Mark one of them as primary or name it 'taskScheduler' " + "(possibly as an alias); or implement the SchedulingConfigurer interface and call " + "ScheduledTaskRegistrar#setScheduler explicitly within the configureTasks() callback: " + ex2.getBeanNamesFound()); } } } catch (NoSuchBeanDefinitionException ex2) { if (logger.isTraceEnabled()) { logger.trace("Could not find default ScheduledExecutorService bean - falling back to default: " + ex2.getMessage()); } // Giving up -> falling back to default scheduler within the registrar... logger.info("No TaskScheduler/ScheduledExecutorService bean found for scheduled processing"); } } } this.registrar.afterPropertiesSet(); }
上述获取任务调度器的优先级顺序为:
1)当Bean后处理器中定义了任务调度器时,优先取Bean后处理器的任务调度器
2)在BeanFactory中获取Bean类型为SchedulingConfigurer的实例,在其方法configureTasks中可以自定义任务调度器
3)获取BeanFactory中TaskScheduler类型的bean(如有)
4)获取BeanFactory中ScheduledExecutorService类型的bean(如有)
5)当上述方式获取的任务调度器都不存在时,会使用框架中默认的任务调度器,如下:
if (this.taskScheduler == null) { this.localExecutor = Executors.newSingleThreadScheduledExecutor(); this.taskScheduler = new ConcurrentTaskScheduler(this.localExecutor); }
3.2 框架内提供的任务调度器
框架内提供的任务调度器主要包括:
1)ConcurrentTaskScheduler
2)ThreadPoolTaskScheduler
继承结构如下:
3.3 任务调度器执行逻辑
以上述框架默认的ConcurrentTaskScheduler进行说明,在调用调度器方法scheduleWithFixedDelay执行时,具体执行逻辑为:
@Override public ScheduledFuture<?> scheduleWithFixedDelay(Runnable task, Date startTime, long delay) { long initialDelay = startTime.getTime() - this.clock.millis(); try { return this.scheduledExecutor.scheduleWithFixedDelay(decorateTask(task, true), initialDelay, delay, TimeUnit.MILLISECONDS); } catch (RejectedExecutionException ex) { throw new TaskRejectedException("Executor [" + this.scheduledExecutor + "] did not accept task: " + task, ex); } }
这里主要包含2部分:
1)首先把task任务包装为DelegatingErrorHandlingRunnable类型(支持嵌入错误处理器逻辑),具体是在方法decorateTask中实现的,如下:
private Runnable decorateTask(Runnable task, boolean isRepeatingTask) { Runnable result = TaskUtils.decorateTaskWithErrorHandler(task, this.errorHandler, isRepeatingTask); if (this.enterpriseConcurrentScheduler) { result = ManagedTaskBuilder.buildManagedTask(result, task.toString()); } return result; } public static DelegatingErrorHandlingRunnable decorateTaskWithErrorHandler( Runnable task, @Nullable ErrorHandler errorHandler, boolean isRepeatingTask) { if (task instanceof DelegatingErrorHandlingRunnable) { return (DelegatingErrorHandlingRunnable) task; } ErrorHandler eh = (errorHandler != null ? errorHandler : getDefaultErrorHandler(isRepeatingTask)); return new DelegatingErrorHandlingRunnable(task, eh); }
2)调用线程池方法scheduleWithFixedDelay进行调度执行
至此,Spring调度框架整体的处理过程总结如下:
开启调度框架(@EnableScheduling)利用bean后处理器识别@Scheduled注解,并包装为Task任务利用任务调度器(TaskScheduler,自定义或框架默认)进行调度执行
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