有谁知道使用 @Resource
和 getBean
获取豆子的过程有何不同?现在我有一个工作的情况:
@Autowired
ApplicationContext applicationContext
public void test() {
Object x = this.applicationContext.getBean("beanName"); //this returns the object I want
}
但这不会:
@Resource(name="beanName")
Object x; //"beanName" can't be found
我想了解这两个过程有何不同,以便我可以开始了解我的错误是什么。
第二个示例的堆栈跟踪。 mainBean
是一个组件扫描的 bean,除了我发布的代码之外,里面没有其他任何东西。
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'mainBean': Injection of resource dependencies failed; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'beanName' is defined
at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessPropertyValues(CommonAnnotationBeanPostProcessor.java:306)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1106)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:517)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:294)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:225)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:291)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:585)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:913)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:464)
at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:385)
at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:284)
at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:111)
at com.ibm.ws.webcontainer.webapp.WebApp.notifyServletContextCreated(WebApp.java:1718)
at com.ibm.ws.webcontainer.webapp.WebApp.commonInitializationFinish(WebApp.java:385)
at com.ibm.ws.webcontainer.webapp.WebAppImpl.initialize(WebAppImpl.java:299)
... 97 more
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'beanName' is defined
at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanDefinition(DefaultListableBeanFactory.java:529)
at org.springframework.beans.factory.support.AbstractBeanFactory.getMergedLocalBeanDefinition(AbstractBeanFactory.java:1095)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:277)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.autowireResource(CommonAnnotationBeanPostProcessor.java:442)
at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.getResource(CommonAnnotationBeanPostProcessor.java:416)
at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor$ResourceElement.getResourceToInject(CommonAnnotationBeanPostProcessor.java:549)
at org.springframework.beans.factory.annotation.InjectionMetadata$InjectedElement.inject(InjectionMetadata.java:150)
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87)
at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessPropertyValues(CommonAnnotationBeanPostProcessor.java:303)
这两个注解都通过 Bean 后处理器工作,该处理器需要在与注释 Bean 相同的上下文中应用(请参阅此处的参考资料):
-
@Autowired
通过AutowiredAnnotationBeanPostProcessor
工作 -
@Resource
(以及其他注释)通过CommonAnnotationBeanPostProcessor
工作
因此,您看到的行为意味着CommonAnnotationBeanPostProcessor
未应用于正在使用@Resource
的 bean。
可以通过以下任一方式激活CommonAnnotationBeanPostProcessor
:
- 将其作为 Bean 显式添加到该特定上下文中
- 通过
<context:annotation-config>
- 通过
<context-annotation-scan>
请注意,这需要在与使用 @Resource
的 bean 相同的春季上下文中完成。
Spring 应用程序可以有多个上下文,例如一个根上下文和多个 servlet 调度程序上下文,另请参阅此答案。
因此,请确保在定义使用 Bean 的 Bean的同一上下文中应用 Bean 后处理器@Resource
。