上一篇文章中我们一下走读了一下spring中实现@Scheduled的源码，想必你对spring中实现定时调度的原理更加了解吧，文末我们两个问题，
1.spring在进行定时调度时，使用的线程池是默认，那么这个默认的线程池的配置是怎样的呢？

2.如何动态调整调度策略。

接下来我们详细分析一下这两个问题。

为@Scheduled定义一个线程池

spring在执行调度任务前，会按照好一定的策略，寻找一个可用的线程池来执行调度任务，寻找这个线程池的过程如下:

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);// 1.使用SchedulingConfigurer进行配置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... // 2.寻找一个类型为 TaskScheduler 的beanthis.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 Sch