java - 如何在 spring-boot 中启用 TaskScheduler？

Question

我正在使用 spring-boot 来设置 spring 默认值。我想使用 @EnableScheduling 机制，并根据条件安排我的任务。

因此我必须实现 SchedulingConfigurer 并显式设置 TaskScheduler。

但是在注入(inject) TaskScheduler 时，出现以下错误。但是为什么spring-boot不自动提供相应的Scheduler呢？

@Configuration
@EnableAutoConfiguration
@EnableScheduling
public class AppConfig {

}

@Service
public class JobService implements SchedulingConfigurer {
    @Autowired
    private TaskScheduler taskScheduler;

    //schedule the task dynamically
    @Override
    public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
        taskRegistrar.setScheduler(taskScheduler); //fails
        taskRegistrar.addTriggerTask(task, trigger);
    }
}

错误:

Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private org.springframework.scheduling.TaskScheduler; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.springframework.scheduling.TaskScheduler] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:561)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:331)
    ... 15 more
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.springframework.scheduling.TaskScheduler] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:1308)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1054)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:949)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:533)
    ... 17 more

Answer 1

您不需要在 ScheduledTaskRegistrar 上设置调度程序。如果尚未配置，则默认为包装单线程计划执行程序的 ConcurrentTaskScheduler:

if (this.taskScheduler == null) {
    this.localExecutor = Executors.newSingleThreadScheduledExecutor();
    this.taskScheduler = new ConcurrentTaskScheduler(this.localExecutor);
}

如果您对这个默认调度程序感到满意，您可以删除 TaskScheduler 的 Autowiring 以及在 ScheduledTaskRegistrar 上设置它的调用。此外，正如 Marten 在评论中所建议的那样，您应该使您的 SchedulingConfigurer 成为配置类而不是服务。

这些更改使您的代码看起来像这样:

@Configuration
static class TaskConfiguration implements SchedulingConfigurer {

    //schedule the task dynamically
    @Override
    public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
        taskRegistrar.addTriggerTask(task, trigger);
    }
}