java - Spring中奇怪的NoSuchBeanDefinitionException

Question

我得到一个经典的 org.springframework.beans.factory.BeanCreationException:

Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'Server': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private MyClass Server.myClass; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [MyClass] 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.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:334)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1214)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:543)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:772)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:839)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:538)
    at org.springframework.context.annotation.AnnotationConfigApplicationContext.<init>(AnnotationConfigApplicationContext.java:84)
    at root.package.Application.main(Application.java:14)
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private MyClass Server.myClass; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [MyClass] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:573)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:331)
    ... 12 more
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [MyClass] 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:1373)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1119)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1014)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:545)
    ... 14 more

上面堆栈跟踪中的“MyClass”当然是我的类的 FQN，在本例中我替换了它(我无法显示我的包)。这是一个简单的 Netty 处理程序:

@Service
public class MyClass extends SimpleChannelInboundHandler<Protocol> implements Visitor {
    @Autowired
    private RestTemplate restTemplate;

    protected void channelRead0(ChannelHandlerContext channelHandlerContext, Protocol protocol) throws Exception {
        channelHandlerContext.writeAndFlush(protocol.accept(this, channelHandlerContext));
    }

    public Object visit(Protocol protocol, ChannelHandlerContext channelHandlerContext) {
        return restTemplate.exchange(...);
    }
}

依赖于MyClass的类:

@Component
public class Server {
    @Autowired
    private MyClass myClass;

    private ChannelFuture serverChannelFuture;

    @PostConstruct
    public void start() throws Exception {
        serverChannelFuture = bootstrap().bind(tcpPort()).sync();
    }

    @PreDestroy
    public void stop() throws Exception {
        serverChannelFuture.channel().close();
        serverChannelFuture.channel().closeFuture().sync();
    }

    private ServerBootstrap bootstrap() {
        // Bootstrap setup
    }
}

我的配置:

@Configuration
@ComponentScan("root.package")
public class SpringConfig {
    @Bean
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }

    @Bean
    public Logger logger() {
        return Logger.getLogger(InternalLoggerFactory.class.toString());
    }
}

我的所有类都位于 root.package 或其子包中。 MyClass 也在子包中。

我不知道为什么这会导致上述异常。我的 root.package 包中有其他正在 Autowiring 的服务!有人有想法吗？

编辑:经过一些进一步的测试，“访问”方法似乎是问题所在。如果我重命名它，应用程序可以正常启动。这可能是 Spring 中的一个错误吗？

编辑2:我庆祝得太早了。我在访问者界面中重命名了该方法，现在又回到了同样的问题。即使我注释掉我的接口(interface)，我也不能拥有与该接口(interface)同名的任何方法。 MyClass 是唯一实现作为 Spring bean 的 Visitor 的类。

Answer 1

你的类MyClass没有包名？

"No qualifying bean of type [MyClass]" 

在您的配置中将组件设置为特定的包

@ComponentScan("root.package")

所以Spring无法找到你的bean。

修复方法:删除(“root.package”)或将包“root.package”添加到您的类中