一、背景
spring boot的定时任务非常简单，只需要在启动类中加上@EnableScheduling注解，然后在对应的方法上配置@Scheduled就可以了，系统会自动处理并按照Scheduled中的配置定时执行方法。
但是在启动项目的时候，发生了很诡异的现象，有两个TaskScheduler/ScheduledExecutorService的异常打印了出来。但是系统并没有受影响，依然正常启动，而且定时任务也是正常执行。
2018-09-29 15:54:05,187 DEBUG main org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor [//] Could not find default TaskScheduler bean
org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'org.springframework.scheduling.TaskScheduler' available
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveNamedBean(DefaultListableBeanFactory.java:996)
at org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor.resolveSchedulerBean(ScheduledAnnotationBeanPostProcessor.java:278)
at org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor.finishRegistration(ScheduledAnnotationBeanPostProcessor.java:221)
at org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor.onApplicationEvent(ScheduledAnnotationBeanPostProcessor.java:200)
at org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor.onApplicationEvent(ScheduledAnnotationBeanPostProcessor.java:94)
at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:167)
at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:383)
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:337)
at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:882)
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.finishRefresh(EmbeddedWebApplicationContext.java:144)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:545)
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122)
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:737)
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:370)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:314)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1162)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1151)
at com.cmft.RunApp.main(RunApp.java:34)
2018-09-29 15:54:05,190 DEBUG main org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor [//] Could not find default ScheduledExecutorService bean
org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'java.util.concurrent.ScheduledExecutorService' available
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveNamedBean(DefaultListableBeanFactory.java:996)
at org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor.resolveSchedulerBean(ScheduledAnnotationBeanPostProcessor.java:278)
at org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor.finishRegistration(ScheduledAnnotationBeanPostProcessor.java:241)
at org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor.onApplicationEvent(ScheduledAnnotationBeanPostProcessor.java:200)
at org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor.onApplicationEvent(ScheduledAnnotationBeanPostProcessor.java:94)
at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:167)
at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:383)
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:337)
at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:882)
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.finishRefresh(EmbeddedWebApplicationContext.java:144)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:545)
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122)
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:737)
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:370)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:314)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1162)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1151)
at com.cmft.RunApp.main(RunApp.java:34)
2018-09-29 15:54:05,190 INFO main org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor [//] No TaskScheduler/ScheduledExecutorService bean found for scheduled processing
二、分析
虽然没有影响系统，但是有异常看着总归很难受，于是尝试去探究下这个异常的原因。
通过观察我们这两个异常是日志模块打印出来的debug级别日志
2018-09-29 15:54:05,187 DEBUG main org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor [//] Could not find default TaskScheduler bean
2018-09-29 15:54:05,190 DEBUG main org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor [//] Could not find default ScheduledExecutorService bean
而且都是在ScheduledAnnotationBeanPostProcessor类中打印出来。看类的名字我们大概能猜到这是@Scheduled注解的处理类。
根据日志内容我们定位到这个问题是由finishRegistration()方法打印出来。
private void finishRegistration() {
if (this.scheduler != null) {
this.registrar.setScheduler(this.scheduler);
}
if (this.beanFactory instanceof ListableBeanFactory) {
Map<String, SchedulingConfigurer> configurers = ((ListableBeanFactory)this.beanFactory).getBeansOfType(SchedulingConfigurer.class);
Iterator var2 = configurers.values().iterator();
while(var2.hasNext()) {
SchedulingConfigurer configurer = (SchedulingConfigurer)var2.next();
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 {
this.registrar.setTaskScheduler((TaskScheduler)this.resolveSchedulerBean(TaskScheduler.class, false));
} catch (NoUniqueBeanDefinitionException var8) {
try {
this.registrar.setTaskScheduler((TaskScheduler)this.resolveSchedulerBean(TaskScheduler.class, true));
} catch (NoSuchBeanDefinitionException var7) {
if (this.logger.isInfoEnabled()) {
this.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: " + var8.getBeanNamesFound());
}
}
} catch (NoSuchBeanDefinitionException var9) {
this.logger.debug("Could not find default TaskScheduler bean", var9);
try {
this.registrar.setScheduler(this.resolveSchedulerBean(ScheduledExecutorService.class, false));
} catch (NoUniqueBeanDefinitionException var5) {
try {
this.registrar.setScheduler(this.resolveSchedulerBean(ScheduledExecutorService.class, true));
} catch (NoSuchBeanDefinitionException var4) {
if (this.logger.isInfoEnabled()) {
this.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: " + var5.getBeanNamesFound());
}
}
} catch (NoSuchBeanDefinitionException var6) {
this.logger.debug("Could not find default ScheduledExecutorService bean", var6);
this.logger.info("No TaskScheduler/ScheduledExecutorService bean found for scheduled processing");
}
}
}
this.registrar.afterPropertiesSet();
}
看代码我们会发现，spring会从先从注册过的bean中找任务调度器TaskScheduler
this.registrar.setTaskScheduler((TaskScheduler)this.resolveSchedulerBean(TaskScheduler.class, false));
如果获取不到会抛出异常，然后打印出来
this.logger.debug("Could not find default TaskScheduler bean", var9);
然后继续寻找定时任务的执行类ScheduledExecutorService
this.registrar.setScheduler(this.resolveSchedulerBean(ScheduledExecutorService.class, false));
如果找不到，会继续抛出异常并打印出来
catch (NoSuchBeanDefinitionException var6) {
this.logger.debug("Could not find default ScheduledExecutorService bean", var6);
this.logger.info("No TaskScheduler/ScheduledExecutorService bean found for scheduled processing");
}
如此，便看到开头我们看到的两个异常。
看后面代码我们会发现，如果注册的bean中找不到，会调用scheduleTasks()方法初始化TaskScheduler，所以这两个异常并不会影响系统。可能spring 的开发者是想借此提醒开发人员要自己在系统中注册要使用的bean,而不是依赖框架来默认初始化。
解决办法
修改日志级别
第一种是眼不见为净法，简单粗暴地修改日志级别就好。
log4j.logger.org.springframework.scheduling = INFO
这样debug级别的日志就不会被打印出来，只有最后的info级别日志才会被打印。
注册TaskScheduler
既然提示的异常是注册的bean中找不到TaskScheduler，那么我们就注册TaskScheduler。
@Bean
public TaskScheduler scheduledExecutorService() {
ThreadPoolTaskScheduler scheduler = new ThreadPoolTaskScheduler();
scheduler.setPoolSize(8);
scheduler.setThreadNamePrefix("scheduled-thread-");
return scheduler;
}
