spring如何设置定时任务详解(@Scheduled)

- 一：注解方式配置定时任务：
- 二：@Scheduled
- 三：原理简介
- 四：其他

xmlns:task="http://www.springframework.org/schema/task"

http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-4.3.xsd"

<task:annotation-driven scheduler="dataScheduler"/>

<task:scheduler id="dataScheduler" pool-size="5"/>

- 注意 下面的案例是在每天的早上2点执行
- “0 0 2 \* \* \*”是怎么组合的？下面会详细介绍@Scheduled()注解

@Scheduled(cron = "0 0 2 * * *")
public void init(){
    todo...
}

@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 -1L;
    String fixedDelayString() default "";
    long fixedRate() default -1L;
    String fixedRateString() default "";
    long initialDelay() default -1L;
    String initialDelayString() default "";
}

public Object postProcessAfterInitialization(Object bean, String beanName) {
    Class<?> targetClass = AopProxyUtils.ultimateTargetClass(bean);
    if (!this.nonAnnotatedClasses.contains(targetClass)) {
        Map<Method, Set<Scheduled>> annotatedMethods = MethodIntrospector.selectMethods(targetClass, new MetadataLookup<Set<Scheduled>>() {
            public Set<Scheduled> inspect(Method method) {
                //获取注解方法
                **Set<Scheduled> scheduledMethods = AnnotatedElementUtils.getMergedRepeatableAnnotations(method, Scheduled.class, Schedules.class);**
                return !scheduledMethods.isEmpty() ? scheduledMethods : null;
            }
        });
        if (annotatedMethods.isEmpty()) {
            ...
        } else {
            Iterator var5 = annotatedMethods.entrySet().iterator();
            while(var5.hasNext()) {

                Entry<Method, Set<Scheduled>> entry = (Entry)var5.next();
                Method method = (Method)entry.getKey();
                Iterator var8 = ((Set)entry.getValue()).iterator();

                while(var8.hasNext()) {
                    Scheduled scheduled = (Scheduled)var8.next();
                    //将获取的任务进行参数解析并存放到任务队列
                    this.processScheduled(scheduled, method, bean);
                }
            }
           ...
        }
    }
    return bean;
}

protected void processScheduled(Scheduled scheduled, Method method, Object bean) {
    try {
        ...
        //解析initialDelayString参数
        String initialDelayString = scheduled.initialDelayString();
        if (StringUtils.hasText(initialDelayString)) {
           ...
        }
        //解析cron参数
        String cron = scheduled.cron();
        if (StringUtils.hasText(cron)) {
            ...
            //存放到任务队列中
            tasks.add(this.registrar.scheduleCronTask(new CronTask(runnable, new CronTrigger(cron, timeZone))));
        }
        ...
        //解析fixedDelay参数
        long fixedDelay = scheduled.fixedDelay();
        if (fixedDelay >= 0L) {
            Assert.isTrue(!processedSchedule, errorMessage);
            processedSchedule = true;
            tasks.add(this.registrar.scheduleFixedDelayTask(new IntervalTask(runnable, fixedDelay, initialDelay)));
        }
        String fixedDelayString = scheduled.fixedDelayString();
        if (StringUtils.hasText(fixedDelayString)) {
            ...
            //存放到任务队列中
            tasks.add(this.registrar.scheduleFixedDelayTask(new IntervalTask(runnable, fixedDelay, initialDelay)));
        }
        //解析fixedRate参数
        long fixedRate = scheduled.fixedRate();
        if (fixedRate >= 0L) {
            Assert.isTrue(!processedSchedule, errorMessage);
            processedSchedule = true;
            tasks.add(this.registrar.scheduleFixedRateTask(new IntervalTask(runnable, fixedRate, initialDelay)));
        }
        String fixedRateString = scheduled.fixedRateString();
        if (StringUtils.hasText(fixedRateString)) {
            ...
            //存放到任务队列中
            tasks.add(this.registrar.scheduleFixedRateTask(new IntervalTask(runnable, fixedRate, initialDelay)));
        }
        Assert.isTrue(processedSchedule, errorMessage);
        Map var19 = this.scheduledTasks;
        //并发控制并将任务存放在map中
        synchronized(this.scheduledTasks) {
            Set<ScheduledTask> registeredTasks = (Set)this.scheduledTasks.get(bean);
            if (registeredTasks == null) {
                registeredTasks = new LinkedHashSet(4);
                //将任务存放在map中
                this.scheduledTasks.put(bean, registeredTasks);
            }
            ((Set)registeredTasks).addAll(tasks);
        }
    } catch (IllegalArgumentException var26) {
        throw new IllegalStateException("Encountered invalid @Scheduled method '" + method.getName() + "': " + var26.getMessage());
    }
}

protected void scheduleTasks() {
    if (this.taskScheduler == null) {
        this.localExecutor = Executors.newSingleThreadScheduledExecutor();
        this.taskScheduler = new ConcurrentTaskScheduler(this.localExecutor);
    }
    Iterator var1;
    if (this.triggerTasks != null) {
        var1 = this.triggerTasks.iterator();
        while(var1.hasNext()) {
            TriggerTask task = (TriggerTask)var1.next();
            this.addScheduledTask(this.scheduleTriggerTask(task));
        }
    }
    if (this.cronTasks != null) {
        var1 = this.cronTasks.iterator();
        while(var1.hasNext()) {
            CronTask task = (CronTask)var1.next();
            this.addScheduledTask(this.scheduleCronTask(task));
        }
    }
    IntervalTask task;
    if (this.fixedRateTasks != null) {
        var1 = this.fixedRateTasks.iterator();
        while(var1.hasNext()) {
            task = (IntervalTask)var1.next();
            this.addScheduledTask(this.scheduleFixedRateTask(task));
        }
    }
    if (this.fixedDelayTasks != null) {
        var1 = this.fixedDelayTasks.iterator();
        while(var1.hasNext()) {
            task = (IntervalTask)var1.next();
            this.addScheduledTask(this.scheduleFixedDelayTask(task));
        }
    }
}