java - 使用 Spring 创建 Scheduler Bean 时出现 NullPointerException

Question

我正在尝试使用 Spring 创建一个调度程序。

@Configuration
@EnableScheduling
public class MyScheduler {


  @Autowired
  MyBusinessService businessService;


  @Scheduled(cron = "* * * * * *")
  public void myCronMethod() {

  }
}

在应用程序启动期间，我收到以下错误:

java.lang.NullPointerException
    at org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor.resolveSchedulerBean(ScheduledAnnotationBeanPostProcessor.java:281)
    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.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:545)
    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:5068)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5584)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1572)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1562)
    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)

在 ScheduledAnnotationBeanPostProcessor 中，holder 为空:

NamedBeanHolder<T> holder = ((AutowireCapableBeanFactory) this.beanFactory).resolveNamedBean(schedulerType);

schedulerType 是:

interface org.springframework.scheduling.TaskScheduler

该应用程序是一个 JSF 应用程序。我使用的是 java 8 和 spring 版本 4.3.6，但是使用 Ant 且没有依赖项管理，因此可能会丢失库或库不匹配。

Answer 1

刚刚在 Kotlin 应用程序中遇到同样的错误，我的解决方法是手动添加一个 TaskScheduler 到我的应用程序配置中:

Java例子取自from here .

@Bean
public ThreadPoolTaskScheduler threadPoolTaskScheduler(){
    ThreadPoolTaskScheduler threadPoolTaskScheduler
      = new ThreadPoolTaskScheduler();
    threadPoolTaskScheduler.setPoolSize(5);
    threadPoolTaskScheduler.setThreadNamePrefix(
      "ThreadPoolTaskScheduler");
    return threadPoolTaskScheduler;
}

我的 Kotlin 版本是

@Bean
fun threadPoolTaskScheduler()
    = ThreadPoolTaskScheduler().apply {
        setPoolSize(5)
        setThreadNamePrefix("ThreadPoolTaskScheduler")
}

(我还没有尝试过，但我相信升级到 Spring 5 也会解决这个问题 - this commit 会在生成空指针的地方抛出一个异常。)