spring 定时器任务深入理解

spring配置文件中配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:task="http://www.springframework.org/schema/task"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context-4.2.xsd
       http://www.springframework.org/schema/mvc
       http://www.springframework.org/schema/mvc/spring-mvc-4.2.xsd
       http://www.springframework.org/schema/aop
       http://www.springframework.org/schema/aop/spring-aop-4.2.xsd
       http://www.springframework.org/schema/task 
       http://www.springframework.org/schema/task/spring-task-3.0.xsd">

    <bean class="com.wjz.quartz.RepayQuartz"/>
    <task:annotation-driven/>
</beans>

定时任务处理类

package com.wjz.quartz;

import org.springframework.scheduling.annotation.Scheduled;

public class RepayQuartz {

    @Scheduled(cron="0/10 * * * * ?")
    public void repay() {
        System.out.println("sping 定时任务");
    }
}

<task:annotation-driven/>标签使用TaskNamespaceHandler 来处理

public class TaskNamespaceHandler extends NamespaceHandlerSupport {

    @Override
    public void init() {
　　　　　// 注册了一些解析器其中AnnotationDrivenBeanDefinitionParser解析@Scheduled注解
        this.registerBeanDefinitionParser("annotation-driven", new AnnotationDrivenBeanDefinitionParser());
        this.registerBeanDefinitionParser("executor", new ExecutorBeanDefinitionParser());
        this.registerBeanDefinitionParser("scheduled-tasks", new ScheduledTasksBeanDefinitionParser());
        this.registerBeanDefinitionParser("scheduler", new SchedulerBeanDefinitionParser());
    }

}

注册了两个后置处理器

org.springframework.scheduling.annotation.AsyncAnnotationBeanPostProcessor

org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor

我们主要来看ScheduledAnnotationBeanPostProcessor

我们可以看到他实现了BeanPostProcesser，ApplicationListener接口

先执行初始化后的后置处理

@Override
    public Object postProcessAfterInitialization(final Object bean, String beanName) {
        Class<?> targetClass = AopUtils.getTargetClass(bean);
        if (!this.nonAnnotatedClasses.contains(targetClass)) {
　　　　　　　// 获得bean的所有的方法，获得方法信息和@Scheduled注解信息
            Map<Method, Set<Scheduled>> annotatedMethods = MethodIntrospector.selectMethods(targetClass,
                    new MethodIntrospector.MetadataLookup<Set<Scheduled>>() {
                        @Override
                        public Set<Scheduled> inspect(Method 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: " + bean.getClass());
                }
            }
            else {
                for (Map.Entry<Method, Set<Scheduled>> entry : annotatedMethods.entrySet()) {
                    Method method = entry.getKey();
                    for (Scheduled scheduled : entry.getValue()) {
　　　　　　　　　　　　　　 // 处理加工方法和注解信息，后文详解
                        processScheduled(scheduled, method, bean);
                    }
                }
                if (logger.isDebugEnabled()) {
                    logger.debug(annotatedMethods.size() + " @Scheduled methods processed on bean '" + beanName +
                            "': " + annotatedMethods);
                }
            }
        }
        return bean;
    }

    protected void processScheduled(Scheduled scheduled, Method method, Object bean) {
        try {
            Method invocableMethod = AopUtils.selectInvocableMethod(method, bean.getClass());
　　　　　　　// 创建了一个Runnable对象，主要是用来反射定时方法的，后文详解#1
            Runnable runnable = new ScheduledMethodRunnable(bean, invocableMethod);
            boolean processedSchedule = false;
            String errorMessage =
                    "Exactly one of the 'cron', 'fixedDelay(String)', or 'fixedRate(String)' attributes is required";
　　　　　　　 // 初始化一个定时任务集合 
            Set<ScheduledTask> tasks = this.scheduledTasks.get(bean);
            if (tasks == null) {
                tasks = new LinkedHashSet<ScheduledTask>(4);
                this.scheduledTasks.put(bean, tasks);
            }

            // 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);
                }
                try {
                    initialDelay = Long.parseLong(initialDelayString);
                }
                catch (NumberFormatException ex) {
                    throw new IllegalArgumentException(
                            "Invalid initialDelayString value "" + initialDelayString + "" - cannot parse into integer");
                }
            }

            // 解析表达式
            String cron = scheduled.cron();
            if (StringUtils.hasText(cron)) {
                Assert.isTrue(initialDelay == -1, "'initialDelay' not supported for cron triggers");
                processedSchedule = true;
                String zone = scheduled.zone();
                if (this.embeddedValueResolver != null) {
                    cron = this.embeddedValueResolver.resolveStringValue(cron);
                    zone = this.embeddedValueResolver.resolveStringValue(zone);
                }
                TimeZone timeZone;
                if (StringUtils.hasText(zone)) {
                    timeZone = StringUtils.parseTimeZoneString(zone);
                }
                else {
　　　　　　　　　　　　// 没有指定时区的话使用默认时区
                    timeZone = TimeZone.getDefault();
                }
　　　　　　　　　 // 将表达式解析成任务计划表填充到任务集合中，后文详解#2
                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 IntervalTask(runnable, fixedDelay, initialDelay)));
            }
            String fixedDelayString = scheduled.fixedDelayString();
            if (StringUtils.hasText(fixedDelayString)) {
                Assert.isTrue(!processedSchedule, errorMessage);
                processedSchedule = true;
                if (this.embeddedValueResolver != null) {
                    fixedDelayString = this.embeddedValueResolver.resolveStringValue(fixedDelayString);
                }
                try {
                    fixedDelay = Long.parseLong(fixedDelayString);
                }
                catch (NumberFormatException ex) {
                    throw new IllegalArgumentException(
                            "Invalid fixedDelayString value "" + fixedDelayString + "" - cannot parse into integer");
                }
                tasks.add(this.registrar.scheduleFixedDelayTask(new IntervalTask(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 IntervalTask(runnable, fixedRate, initialDelay)));
            }
            String fixedRateString = scheduled.fixedRateString();
            if (StringUtils.hasText(fixedRateString)) {
                Assert.isTrue(!processedSchedule, errorMessage);
                processedSchedule = true;
                if (this.embeddedValueResolver != null) {
                    fixedRateString = this.embeddedValueResolver.resolveStringValue(fixedRateString);
                }
                try {
                    fixedRate = Long.parseLong(fixedRateString);
                }
                catch (NumberFormatException ex) {
                    throw new IllegalArgumentException(
                            "Invalid fixedRateString value "" + fixedRateString + "" - cannot parse into integer");
                }
                tasks.add(this.registrar.scheduleFixedRateTask(new IntervalTask(runnable, fixedRate, initialDelay)));
            }

            // Check whether we had any attribute set
            Assert.isTrue(processedSchedule, errorMessage);
        }
        catch (IllegalArgumentException ex) {
            throw new IllegalStateException(
                    "Encountered invalid @Scheduled method '" + method.getName() + "': " + ex.getMessage());
        }
    }

书接前文#1

Runnable的run方法中是定时方法反射

    @Override
    public void run() {
        try {
            ReflectionUtils.makeAccessible(this.method);
            this.method.invoke(this.target);
        }
        catch (InvocationTargetException ex) {
            ReflectionUtils.rethrowRuntimeException(ex.getTargetException());
        }
        catch (IllegalAccessException ex) {
            throw new UndeclaredThrowableException(ex);
        }
    }

书接前文#2

创建一个CronTask任务对象，其中有Runnable对象和CronTrigger触发对象（表达式，时区），后文详解触发器的构造#2-1

public ScheduledTask scheduleCronTask(CronTask task) {
        ScheduledTask scheduledTask = this.unresolvedTasks.remove(task);
        boolean newTask = false;
        if (scheduledTask == null) {
            scheduledTask = new ScheduledTask();
            newTask = true;
        }
        if (this.taskScheduler != null) {
　　　　　　　 // 执行定时任务
            scheduledTask.future = this.taskScheduler.schedule(task.getRunnable(), task.getTrigger());
        }
        else {
　　　　　　　 // 添加定时任务
            addCronTask(task);
            this.unresolvedTasks.put(task, scheduledTask);
        }
        return (newTask ? scheduledTask : null);
    }

再看监听处理

    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {
        if (event.getApplicationContext() == this.applicationContext) {
            // Running in an ApplicationContext -> register tasks this late...
            // giving other ContextRefreshedEvent listeners a chance to perform
            // their work at the same time (e.g. Spring Batch's job registration).
            finishRegistration();
        }
    }

this.registrar.afterPropertiesSet();

protected void scheduleTasks() {
        if (this.taskScheduler == null) {
　　　　　　　 // 初始化一个线程池调度器
            this.localExecutor = Executors.newSingleThreadScheduledExecutor();
　　　　　　　 // 指定了任务调度器
            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));
            }
        }
    }

public ScheduledTask scheduleCronTask(CronTask task) {
        ScheduledTask scheduledTask = this.unresolvedTasks.remove(task);
        boolean newTask = false;
        if (scheduledTask == null) {
            scheduledTask = new ScheduledTask();
            newTask = true;
        }
　　　　　// 这次指定了ConcurrentTaskScheduler任务调度器，开始调度定时任务
        if (this.taskScheduler != null) {
            scheduledTask.future = this.taskScheduler.schedule(task.getRunnable(), task.getTrigger());
        }
        else {
            addCronTask(task);
            this.unresolvedTasks.put(task, scheduledTask);
        }
        return (newTask ? scheduledTask : null);
    }

@Override
    public ScheduledFuture<?> schedule(Runnable task, Trigger trigger) {
        try {
            if (this.enterpriseConcurrentScheduler) {
                return new EnterpriseConcurrentTriggerScheduler().schedule(decorateTask(task, true), trigger);
            }
            else {
                ErrorHandler errorHandler = (this.errorHandler != null ? this.errorHandler : TaskUtils.getDefaultErrorHandler(true));
　　　　　　　　　 // 这里就是核心的地方了， Runnable的run方法内，定时调用自己的run方法实现功能，巧妙之极
                return new ReschedulingRunnable(task, trigger, this.scheduledExecutor, errorHandler).schedule();
            }
        }
        catch (RejectedExecutionException ex) {
            throw new TaskRejectedException("Executor [" + this.scheduledExecutor + "] did not accept task: " + task, ex);
        }
    }

public ScheduledFuture<?> schedule() {
        synchronized (this.triggerContextMonitor) {
　　　　　　　 // 拿到下一次执行任务的时间，后文详解#2-2
            this.scheduledExecutionTime = this.trigger.nextExecutionTime(this.triggerContext);
            if (this.scheduledExecutionTime == null) {
                return null;
            }
　　　　　　　 // 固定延迟即延迟多长时间执行
            long initialDelay = this.scheduledExecutionTime.getTime() - System.currentTimeMillis();
            this.currentFuture = this.executor.schedule(this, initialDelay, TimeUnit.MILLISECONDS);
            return this;
        }
    }

    @Override
    public void run() {
        Date actualExecutionTime = new Date();
　　　　　// 这就是上文所提到的定时方法反射执行定时业务方法
        super.run();
        Date completionTime = new Date();
        synchronized (this.triggerContextMonitor) {
　　　　　　　 // 记录上一次任务执行的时间
            this.triggerContext.update(this.scheduledExecutionTime, actualExecutionTime, completionTime);
            if (!this.currentFuture.isCancelled()) {
　　　　　　　　　 // 继续无限调度
                schedule();
            }
        }
    }

 书接前文#2-1

CronTrigger触发对象的构造，初始化了计划时间表生成器

public CronTrigger(String expression, TimeZone timeZone) {
        this.sequenceGenerator = new CronSequenceGenerator(expression, timeZone);
    }

public CronSequenceGenerator(String expression, TimeZone timeZone) {
        this.expression = expression;
        this.timeZone = timeZone;
　　　　　// 解析表达式生成计划时间表
        parse(expression);
    }

private void parse(String expression) throws IllegalArgumentException {
        String[] fields = StringUtils.tokenizeToStringArray(expression, " ");
        if (!areValidCronFields(fields)) {
            throw new IllegalArgumentException(String.format(
                    "Cron expression must consist of 6 fields (found %d in "%s")", fields.length, expression));
        }
　　　　　// 主要使用了BitSet来制造计划时间表
        setNumberHits(this.seconds, fields[0], 0, 60);
        setNumberHits(this.minutes, fields[1], 0, 60);
        setNumberHits(this.hours, fields[2], 0, 24);
        setDaysOfMonth(this.daysOfMonth, fields[3]);
        setMonths(this.months, fields[4]);
        setDays(this.daysOfWeek, replaceOrdinals(fields[5], "SUN,MON,TUE,WED,THU,FRI,SAT"), 8);
        if (this.daysOfWeek.get(7)) {
            // Sunday can be represented as 0 or 7
            this.daysOfWeek.set(0);
            this.daysOfWeek.clear(7);
        }
    }

private void setNumberHits(BitSet bits, String value, int min, int max) {
        String[] fields = StringUtils.delimitedListToStringArray(value, ",");
        for (String field : fields) {
　　　　　　　// 检查是否包含'/',不包含的话列出最小值到最大值的范围
            if (!field.contains("/")) {
                // Not an incrementer so it must be a range (possibly empty)
                int[] range = getRange(field, min, max);
                bits.set(range[0], range[1] + 1);
            }
            else {
                // 包含'/'的话列出每xx秒（或分、时）的时间表如{0,10,20,30,40,50}
                String[] split = StringUtils.delimitedListToStringArray(field, "/");
                if (split.length > 2) {
                    throw new IllegalArgumentException("Incrementer has more than two fields: '" +
                            field + "' in expression "" + this.expression + """);
                }
                int[] range = getRange(split[0], min, max);
                if (!split[0].contains("-")) {
                    range[1] = max - 1;
                }
                int delta = Integer.valueOf(split[1]);
                if (delta <= 0) {
                    throw new IllegalArgumentException("Incrementer delta must be 1 or higher: '" +
                            field + "' in expression "" + this.expression + """);
                }
　　　　　　　　　 // 以一定数值叠加为BitSet赋值
                for (int i = range[0]; i <= range[1]; i += delta) {
                    bits.set(i);
                }
            }
        }
    }

private int[] getRange(String field, int min, int max) {
        int[] result = new int[2];
　　　　　// 包含*就是最大到最小
        if (field.contains("*")) {
            result[0] = min;
            result[1] = max - 1;
            return result;
        }
　　　　　// 不包含'/'和'-'返回值
        if (!field.contains("-")) {
            result[0] = result[1] = Integer.valueOf(field);
        }
        else {
            String[] split = StringUtils.delimitedListToStringArray(field, "-");
            if (split.length > 2) {
                throw new IllegalArgumentException("Range has more than two fields: '" +
                        field + "' in expression "" + this.expression + """);
            }
            result[0] = Integer.valueOf(split[0]);
            result[1] = Integer.valueOf(split[1]);
        }
        if (result[0] >= max || result[1] >= max) {
            throw new IllegalArgumentException("Range exceeds maximum (" + max + "): '" +
                    field + "' in expression "" + this.expression + """);
        }
        if (result[0] < min || result[1] < min) {
            throw new IllegalArgumentException("Range less than minimum (" + min + "): '" +
                    field + "' in expression "" + this.expression + """);
        }
        if (result[0] > result[1]) {
            throw new IllegalArgumentException("Invalid inverted range: '" + field +
                    "' in expression "" + this.expression + """);
        }
        return result;
    }

书接前文#2-2

拿到下一个执行调度的时间

@Override
    public Date nextExecutionTime(TriggerContext triggerContext) {
　　　　　// 拿到上一次执行调度的时间
        Date date = triggerContext.lastCompletionTime();
        if (date != null) {
            Date scheduled = triggerContext.lastScheduledExecutionTime();
            if (scheduled != null && date.before(scheduled)) {
                date = scheduled;
            }
        }
        else {
　　　　　　　 // 没拿到的话就拿当前时间
            date = new Date();
        }
　　　　　// 拿到一下一次执行调度的时间
        return this.sequenceGenerator.next(date);
    }

public Date next(Date date) {

        Calendar calendar = new GregorianCalendar();
        calendar.setTimeZone(this.timeZone);
        calendar.setTime(date);

        calendar.set(Calendar.MILLISECOND, 0);
        long originalTimestamp = calendar.getTimeInMillis();
　　　　　// 为日历设置下一次执行调度的时间
        doNext(calendar, calendar.get(Calendar.YEAR));

        if (calendar.getTimeInMillis() == originalTimestamp) {
            calendar.add(Calendar.SECOND, 1);
            doNext(calendar, calendar.get(Calendar.YEAR));
        }
　　　　　// 返回设置好下一次调度的日历时间
        return calendar.getTime();
    }

private void doNext(Calendar calendar, int dot) {
        List<Integer> resets = new ArrayList<Integer>();
　　　　　// 拿到当前时间的秒数
        int second = calendar.get(Calendar.SECOND);
        List<Integer> emptyList = Collections.emptyList();
　　　　　// 拿到下一次执行调度的秒数
        int updateSecond = findNext(this.seconds, second, calendar, Calendar.SECOND, Calendar.MINUTE, emptyList);
        if (second == updateSecond) {
            resets.add(Calendar.SECOND);
        }

        int minute = calendar.get(Calendar.MINUTE);
        int updateMinute = findNext(this.minutes, minute, calendar, Calendar.MINUTE, Calendar.HOUR_OF_DAY, resets);
        if (minute == updateMinute) {
            resets.add(Calendar.MINUTE);
        }
        else {
            doNext(calendar, dot);
        }

        int hour = calendar.get(Calendar.HOUR_OF_DAY);
        int updateHour = findNext(this.hours, hour, calendar, Calendar.HOUR_OF_DAY, Calendar.DAY_OF_WEEK, resets);
        if (hour == updateHour) {
            resets.add(Calendar.HOUR_OF_DAY);
        }
        else {
            doNext(calendar, dot);
        }

        int dayOfWeek = calendar.get(Calendar.DAY_OF_WEEK);
        int dayOfMonth = calendar.get(Calendar.DAY_OF_MONTH);
        int updateDayOfMonth = findNextDay(calendar, this.daysOfMonth, dayOfMonth, daysOfWeek, dayOfWeek, resets);
        if (dayOfMonth == updateDayOfMonth) {
            resets.add(Calendar.DAY_OF_MONTH);
        }
        else {
            doNext(calendar, dot);
        }

        int month = calendar.get(Calendar.MONTH);
        int updateMonth = findNext(this.months, month, calendar, Calendar.MONTH, Calendar.YEAR, resets);
        if (month != updateMonth) {
            if (calendar.get(Calendar.YEAR) - dot > 4) {
                throw new IllegalArgumentException("Invalid cron expression "" + this.expression +
                        "" led to runaway search for next trigger");
            }
            doNext(calendar, dot);
        }

    }

private int findNext(BitSet bits, int value, Calendar calendar, int field, int nextField, List<Integer> lowerOrders) {
　　　　　// 拿到下一个执行调度的秒数如当前时间的秒数是23任务是每10秒调度则拿到30，如果是58则返回-1
        int nextValue = bits.nextSetBit(value);
        if (nextValue == -1) {
　　　　　　　 // 加一分（时，日）
            calendar.add(nextField, 1);
　　　　　　　 // 重置秒（分、时）
            reset(calendar, Arrays.asList(field));
            nextValue = bits.nextSetBit(0);
        }
        if (nextValue != value) {
　　　　　　　 // 为日历设置下一个执行调度的秒（分、时）数
            calendar.set(field, nextValue);
            reset(calendar, lowerOrders);
        }
        return nextValue;
    }