springBoot 动态传参数的定时任务的源码分析之SchedulingConfigurer 接口

不念不忘少年蓝@ 2022-10-27 02:23 326阅读 0赞

前篇 我们分析了springBoot 动态传参数的定时任务的使用，今天我们进行其源码分析：

一、启动类源码上注解  @EnableScheduling 已经分析过  [源码分析][Link 1]

二、动态定时任务代码实现结构

@Override
        public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
            taskRegistrar.addTriggerTask(
                    //1.添加任务内容(Runnable)
                    () -> {
                        System.out.println("执行动态定时任务: ";
                        //定时任务业务代码
                    },
                    //2.设置执行周期(Trigger)
                    triggerContext -> {
                        //2.1 从数据库获取执行周期
                        String cron = "";
                        System.out.println("cron="+cron);
                        //2.2 合法性校验.
                        if (StringUtils.isEmpty(cron)) {
                            // Omitted Code ..
                            return null;
                        }
                        //2.3 返回执行周期(Date)
                        return new CronTrigger(cron).nextExecutionTime(triggerContext);
                    }
            );
        }

二、分析接口 SchedulingConfigurer 及实现类

1、SchedulingConfigurer 接口

@FunctionalInterface
    public interface SchedulingConfigurer {
    
    	/**
    	 * Callback allowing a {@link org.springframework.scheduling.TaskScheduler
    	 * TaskScheduler} and specific {@link org.springframework.scheduling.config.Task Task}
    	 * instances to be registered against the given the {@link ScheduledTaskRegistrar}.
    	 * @param taskRegistrar the registrar to be configured.
    	 */
        //有个主要参数 ScheduledTaskRegistrar 
    	void configureTasks(ScheduledTaskRegistrar taskRegistrar);
    
    }

2、点击 ScheduledTaskRegistrar 类进入：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70][]

3、此业务场景的定时任务主要用  如下方法：

/**
    	 * Add a Runnable task to be triggered per the given {@link Trigger}.
    	 * @see TaskScheduler#scheduleAtFixedRate(Runnable, long)
    	 */
        //一个线程任务参数，一个定时器参数
    	public void addTriggerTask(Runnable task, Trigger trigger) {
    		addTriggerTask(new TriggerTask(task, trigger));
    	}

即两个参数的实现类，这里可采用函数式编程（两个接口参数里，均有一个方法），如下代码：

Runnel接口：

@FunctionalInterface
    public interface Runnable {
        /**
         * When an object implementing interface <code>Runnable</code> is used
         * to create a thread, starting the thread causes the object's
         * <code>run</code> method to be called in that separately executing
         * thread.
         * <p>
         * The general contract of the method <code>run</code> is that it may
         * take any action whatsoever.
         *
         * @see     java.lang.Thread#run()
         */
        public abstract void run();
    }

Trigger 接口：

public interface Trigger {
    
    	/**
    	 * Determine the next execution time according to the given trigger context.
    	 * @param triggerContext context object encapsulating last execution times
    	 * and last completion time
    	 * @return the next execution time as defined by the trigger,
    	 * or {@code null} if the trigger won't fire anymore
    	 */
    	@Nullable
    	Date nextExecutionTime(TriggerContext triggerContext);
    
    }

对 nextExecutionTime 方法的实现就是返回一个时间，里面的核心代码如下：

//定时任务触发,可修改定时任务的执行周期
      CronTrigger trigger=new CronTrigger(cron);
      Date nextExecDate= trigger.nextExecutionTime(triggerContext);//点击查看源码

源码如下：

@Override
    	public Date nextExecutionTime(TriggerContext triggerContext) {
    		Date date = triggerContext.lastCompletionTime();
    		if (date != null) {
    			Date scheduled = triggerContext.lastScheduledExecutionTime();
    			if (scheduled != null && date.before(scheduled)) {
    				// Previous task apparently executed too early...
    				// Let's simply use the last calculated execution time then,
    				// in order to prevent accidental re-fires in the same second.
    				date = scheduled;
    			}
    		}
    		else {
    			date = new Date();
    		}
    		return this.sequenceGenerator.next(date);
    	}

4、延伸到此，我们查看 此处源码：

addTriggerTask(new TriggerTask(task, trigger));

TriggerTask 此处为执行业务类：点击进入

public TriggerTask(Runnable runnable, Trigger trigger) {
    		super(runnable);
    		Assert.notNull(trigger, "Trigger must not be null");
    		this.trigger = trigger;
    	}

5、进入 addTriggerTask 方法

/**
    	 * Add a {@code TriggerTask}.
    	 * @since 3.2
    	 * @see TaskScheduler#scheduleAtFixedRate(Runnable, long)
    	 */
    	public void addTriggerTask(TriggerTask task) {
    		if (this.triggerTasks == null) {
    			this.triggerTasks = new ArrayList<>();
    		}
    		this.triggerTasks.add(task);//任务放入list集合中等待执行
    	}

6、何时执行 triggerTasks  中的任务呢？源码发现初始化时执行：

/**
    	 * Calls {@link #scheduleTasks()} at bean construction time.
    	 */
    	@Override
    	public void afterPropertiesSet() {
    		scheduleTasks();//点击查看
    	}

7、进入 scheduleTasks() 方法：

/**
    	 * Schedule all registered tasks against the underlying
    	 * {@linkplain #setTaskScheduler(TaskScheduler) task scheduler}.
    	 */
    	@SuppressWarnings("deprecation")
    	protected 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));//执行此处核心代码，进入
    			}
    		}
    		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));
    			}
    		}
    	}

8、进入 scheduleTriggerTask(task) 方法：

/**
    	 * Schedule the specified trigger task, either right away if possible
    	 * or on initialization of the scheduler.
    	 * @return a handle to the scheduled task, allowing to cancel it
    	 * @since 4.3
    	 */
    	@Nullable
    	public ScheduledTask scheduleTriggerTask(TriggerTask task) {
    		ScheduledTask scheduledTask = this.unresolvedTasks.remove(task);
    		boolean newTask = false;
    		if (scheduledTask == null) {
    			scheduledTask = new ScheduledTask(task);
    			newTask = true;
    		}
    		if (this.taskScheduler != null) {//执行如下代码
    			scheduledTask.future = this.taskScheduler.schedule(task.getRunnable(), task.getTrigger());
    		}
    		else {
    			addTriggerTask(task);
    			this.unresolvedTasks.put(task, scheduledTask);
    		}
    		return (newTask ? scheduledTask : null);
    	}

9、ctrl+t 进入 taskScheduler.schedule 方法：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 1][]

进入线程池执行此任务：

@Override
    	@Nullable
    	public ScheduledFuture<?> schedule(Runnable task, Trigger trigger) {
    		ScheduledExecutorService executor = getScheduledExecutor();
    		try {
    			ErrorHandler errorHandler = this.errorHandler;
    			if (errorHandler == null) {
    				errorHandler = TaskUtils.getDefaultErrorHandler(true);
    			}
                //此处执行定时任务，点击进入
    			return new ReschedulingRunnable(task, trigger, executor, errorHandler).schedule();
    		}
    		catch (RejectedExecutionException ex) {
    			throw new TaskRejectedException("Executor [" + executor + "] did not accept task: " + task, ex);
    		}
    	}

10、进入 schedule() 方法：

@Nullable
    	public ScheduledFuture<?> schedule() {
    		synchronized (this.triggerContextMonitor) {
    			this.scheduledExecutionTime = this.trigger.nextExecutionTime(this.triggerContext);
    			if (this.scheduledExecutionTime == null) {
    				return null;
    			}
    			long initialDelay = this.scheduledExecutionTime.getTime() - System.currentTimeMillis();
    			this.currentFuture = this.executor.schedule(this, initialDelay, TimeUnit.MILLISECONDS);//正式执行此任务
    			return this;
    		}
    	}

进入：ScheduledThreadPoolExecutor 类

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 2][]

源码方法：

/**
         * @throws RejectedExecutionException {@inheritDoc}
         * @throws NullPointerException       {@inheritDoc}
         */
        public ScheduledFuture<?> schedule(Runnable command,
                                           long delay,
                                           TimeUnit unit) {
            if (command == null || unit == null)
                throw new NullPointerException();
            RunnableScheduledFuture<?> t = decorateTask(command,
                new ScheduledFutureTask<Void>(command, null,
                                              triggerTime(delay, unit)));
            delayedExecute(t);//继续执行
            return t;
        }

点击 delayedExecute(t) 方法：

//此处到了底层执行代码
     private void delayedExecute(RunnableScheduledFuture<?> task) {
            if (isShutdown())
                reject(task);
            else {
                super.getQueue().add(task);
                if (isShutdown() &&
                    !canRunInCurrentRunState(task.isPeriodic()) &&
                    remove(task))
                    task.cancel(false);
                else
                    ensurePrestart();//方法进入父类 ThreadPoolExecutor 中执行
            }
        }

到此 动态传参定时任务源码分析完成，大家可以多看几次，就熟悉源码了。

[Link 1]: https://blog.csdn.net/nandao158/article/details/113573787
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70]: /images/20221024/61ba4cb850544fc2848e1fa59163cd1e.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 1]: /images/20221024/505e405a02e24a3193792c0475f7d48a.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 2]: /images/20221024/877c2cde6e65426d97f5a3cedbfa2fa5.png