Spring 定時器 No qualifying bean of type [org.springframework.scheduling.TaskScheduler] is defined
阿新 • • 發佈：2019-02-19
最近專案裡面，用了spring的定時任務，一直以來，專案執行的不錯。定時器也能正常使用。可是，今天啟動專案測試的時候，盯著啟動Log看了一陣子，突然間發現，啟動的Log中居然有一個異常，雖然一閃而過，但是那熟悉的異常格式還是讓我渾身一顫。這個專案一直執行的很好啊，沒發現有什麼問題，怎麼會出現異常呢？
於是我仔細的翻啊翻啊，查啊找啊，嘿，還真的找到了兩個異常：
[2016-10-12 22:49:10,184] [DEBUG] (ScheduledAnnotationBeanPostProcessor.java:finishRegistration:207) Could not find default TaskScheduler bean org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.springframework.scheduling.TaskScheduler] is defined at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:372) at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:332) at org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor.finishRegistration(ScheduledAnnotationBeanPostProcessor.java:192) at org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor.onApplicationEvent(ScheduledAnnotationBeanPostProcessor.java:171) at org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor.onApplicationEvent(ScheduledAnnotationBeanPostProcessor.java:86) at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:163) at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:136) at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:381) at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:335) at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:855) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:541) at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:444) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:326) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:107) at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4812) at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5255) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1408) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1398) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) [2016-10-12 22:49:10,188] [DEBUG] (ScheduledAnnotationBeanPostProcessor.java:finishRegistration:219) Could not find default ScheduledExecutorService bean org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.springframework.scheduling.TaskScheduler] is defined at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:372) at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:332) at org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor.finishRegistration(ScheduledAnnotationBeanPostProcessor.java:192) at org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor.onApplicationEvent(ScheduledAnnotationBeanPostProcessor.java:171) at org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor.onApplicationEvent(ScheduledAnnotationBeanPostProcessor.java:86) at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:163) at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:136) at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:381) at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:335) at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:855) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:541) at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:444) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:326) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:107) at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4812) at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5255) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1408) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1398) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745)
暈啊，很明顯這是定時任務的異常啊。可是定時任務明明能夠正常執行啊，怎麼回事？
嘗試著刪掉了所有的定時任務配置，果然異常消失了。但是隻要啟用任何一個定時任務，異常都會再次出現。這可真可怕。作為一個強迫症患者，不能放任這樣的異常存在，於是仔細的查找了半天，卻依舊沒有結果。最後只好放大招，讀spring的原始碼啦，這一讀，可好，差點沒把我鬱悶死。
為什麼鬱悶呢？ 不知道讀這篇文章的朋友們有沒有細心的，有沒有注意這兩個異常有一個非常特別的地方。什麼地方呢？ 這兩個異常的級別，不是ERROR 也不是 WARNING
居然是DEBUG
原來，Spring的定時任務排程器會嘗試獲取一個註冊過的 task scheduler來做任務排程，它會嘗試通過BeanFactory.getBean的方法來獲取一個註冊過的scheduler bean，獲取的步驟如下：
1.嘗試從配置中找到一個TaskScheduler Bean
2.尋找ScheduledExecutorService Bean
3.使用預設的scheduler
前兩步，如果找不到的話，就會以debug的方式丟擲異常，分別是：
logger.debug("Could not find default TaskScheduler bean", ex);
logger.debug("Could not find default ScheduledExecutorService bean", ex);
所以，日誌中打印出來的兩個異常，根本不是什麼錯誤資訊，也不會影響定時器的使用，只不過是spring的自己列印的一些資訊罷了，不過沒搞明白，為什麼非要用異常的方式打出來，估計是為了看這清晰點吧。也或者，這裡面有一些重要的資訊需要提示開發者。具體是什麼原因，只能有機會進一步再去了解了。