通过请求范围 bean 在单例服务/控制器中的 Spring Boot 自动装配字段

Question

我有一个带有自动装配字段的单例服务类，例如：

@Service
public class MyService{

     @Autowired
     private List<POJO> listWithObjectsForRequest;

}

listWithObjectsForRequest 用于我的 Spring Boot 应用程序的多个服务和组件，并且需要进行大量计算才能创建此列表。它还取决于正在运行的当前请求。所以我想我可以写一个请求范围的bean，每次请求进入我的应用程序时，Spring都会注入它：

@Configuration
public class MyServiceConfiguration{

    @Bean
    @RequestScope
    public List<POJO> listWithObjectsForRequest(){
        return heavyCalculations() // signature: public List<POJO> heavyCalculations()...
    }

}

但我在应用程序启动时收到以下错误：

Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'myService': Unsatisfied dependency expressed through field 'listWithObjectsForRequest'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'scopedTarget.listWithObjectsForRequest': 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.
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:596)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:90)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:374)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1411)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:592)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:277)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1247)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1167)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:593)
    ... 31 common frames omitted
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'scopedTarget.listWithObjectsForRequest': 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.
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:365)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
    at org.springframework.aop.target.SimpleBeanTargetSource.getTarget(SimpleBeanTargetSource.java:35)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:193)
    at com.sun.proxy.$Proxy84.equals(Unknown Source)
    at java.util.concurrent.ConcurrentHashMap.containsValue(ConcurrentHashMap.java:985)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.determineAutowireCandidate(DefaultListableBeanFactory.java:1501)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1222)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1167)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:593)
    ... 44 common frames omitted
Caused by: 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.
    at org.springframework.web.context.request.RequestContextHolder.currentRequestAttributes(RequestContextHolder.java:131)
    at org.springframework.web.context.request.AbstractRequestAttributesScope.get(AbstractRequestAttributesScope.java:42)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:353)
    ... 53 common frames omitted

我以为我在这里找到了答案：Inject request scoped bean into another bean，但我的应用程序仍然失败并显示此错误消息。

我知道listWithObjectsForRequest只能在请求范围内计算，但是如何告诉spring MyService的字段应该只在请求中初始化（一次）？

Answer 1

正如在其他答案中已经提到的，您收到此错误是因为将请求范围的 bean 注入单例范围的 bean 也就是窄 bean DI 问题

你只需要使用

@Autowired // provider from javax.inject.Provider; private Provider<List<POJO>> listWithObjectsForRequest;

参考文献 When to use javax.inject.Provider in Spring?

Answer 2

您将收到此异常，因为您试图将请求范围注入单例。单例将被创建一次，依赖项将被注入一次。您可能正在使用一些依赖于请求的功能，并且在单例的 bean 初始化期间，spring 无法找到它。

如果你想将请求范围 bean 注入到单例中，你可以这样做

将 ApplicationContext 注入 MyService 就像 -

        @Autowired
        private ApplicationContext context;

然后每次都从应用程序上下文中获取 bean 引用，而不是自动装配 listWithObjectsForRequest。虽然这种方法可以解决问题，但会将您的代码与 Spring 绑定。如果你对它没问题，你可以使用它。

或者

您可以使用这里提到的方法注入 - https://docs.spring.io/spring/docs/current/spring-framework-reference/core.html#beans-factory-method-injection

Answer 3

在 POJO 类中 尝试 @Scope("原型") 在类声明之前