Spring 引导：无法访问 Spring 调度程序中的请求 scope bean

Question

In my Spring Boot application, i've a Scheduler task which executes for every one hour. In the scheduler method trying to access the request-scope bean. Always getting the exception org.springframework.beans.factory.BeanCreationException .

Here is the code sample.

@Data
public class TestVo {
  private String message = "Hello";
}

@Bean
@Scope(value="request", proxyMode=ScopedProxyMode.TARGET_CLASS)
public TestVo testVo() {
    return new TestVo();
}

Accessing the above created bean in scheduler method as below,

@Autowired
private TestVo testVo;

@Scheduled(cron="0 0 * * * *")
public void greetings() {
  System.out.println(testVo.getMessage()); // accessing request scope bean
}

getting below exception with above code,

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'scopedTarget.scheduledJobTaskExecutor': Scope 'request' is not active for the current thread; consider defining a scoped proxy for this bean if you intend to refer to it from a singleton; nested exception is java.lang.IllegalStateException: No thread-bound request found: Are you referring to request attributes outside of an actual web request, or processing a request outside of the originally receiving thread? If you are actually operating within a web request and still receive this message, your code is probably running outside of DispatcherServlet: In this case, use RequestContextListener or RequestContextFilter to expose the current request.

will be helpful.. thanks.

Answer 1

The request scoped beans are bounded to specific requests. Every time a request comes, a new instance will be created and after the request finished it will be destroyed. The request is bounded to a thread and use that thread to process the request (in non reactive environment). Even if it was possible, the scheduler wouldnt know, which request object it should use in this situation. Consider you have 100 active request when the scheduled job starts to run, how it should choose one? Or if there arent any active request (so no instance hold by the context?). You can inject request scope into singleton via proxy because the singleton method call will be handled on the same request thread, but the scheduled job use its own thread pool, which not bounded to any requests. Maybe now you can see the problem using request scoped bean in the scheduler. If you want to use the same logic in the scheduler and in request scoped beans, you can for example extract it into a superclass.