先看如下两个注入到spring容器中的bean， 一个是 UserNewManager， 一个是 UserManager。
@Service
public class UserNewManager {public void doSomething() {}}
@Service
public class UserManager {...
}
再看下面的testcase，利用@Resource注解来注入bean。
@SpringBootTest
@RunWith(SpringRunner.class)
public class ResourceTest {@Resourceprivate UserNewManager userManager;@Testpublic void test() {userManager.doSomething();}
}
在运行test方法时，会抛异常：
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'springtrans.resourcetest.ResourceTest': Injection of resource dependencies failed;
nested exception is org.springframework.beans.factory.BeanNotOfRequiredTypeException:
Bean named 'userManager' is expected to be of type 'springtrans.resourcetest.UserNewManager' but was
actually of type 'springtrans.resourcetest.UserManager'
原因：@Resource注解有两个重要的属性：name和type。在一个使用@Resource来注入bean的声明语句中，@Resource优先是按name来解析bean的，当无法解析到bean时会再按照声明type来解析bean，解析完成后注入到对象上。在此testcase案例中，@Resource先按照“userManager”定位到了UserManager这个type，而这个UserManager与实际期望的类型 UserNewManager 产生冲突。就报这个 BeanNotOfRequiredTypeException 异常。 另一种情况，假如容器里没有UserManager这个bean的话，@Resource按照“userManager”就无法解析到type，它会继续按照声明的UserNewManager这个type来解析bean。
我们的项目分为三层，service层→manager层→mapper层，上层依赖下层，相同层级之间一般不相互依赖。其中manager层有一个DataCacheManager，用来做数据缓存。我在一次代码重构中，为了规避未来可能产生的循环引用，我将 DataCacheManager依赖的其他manager改为依赖对应mapper。 例如：我将 @Resource private WorkTypeManager workTypeManager; 改为了 @Resource private WorkTypeMapper workTypeManager; 。结果，在启动springboot服务时，就出现了这个 BeanNotOfRequiredTypeException：Bean named 'workTypeManager' is expected to be of type 'com.xxx.mapper.WorkTypeMapper'but was actually of type 'com.xxx.manager.workTypeManager$$EnhancerBySpringCGLIB$$30dd8c09'。 详细堆栈如下：
2023-08-03 22:30:48.588 [TID:N/A] [] [main] INFO o.a.d.s.b.c.e.AwaitingNonWebApplicationListener:162 - [Dubbo] Current Spring Boot Application is about to shutdown...
2023-08-03 22:30:48.619 [TID:N/A] [] [main] ERROR org.springframework.boot.SpringApplication:858 - Application run failedorg.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'taskApplyDesignImportUserService': Unsatisfied dependency expressed through field'taskApplyManager'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'taskApplyManager': Unsatisfied dependency expressed through field 'dataCacheManager'; nested exception is org.springframework.beans.factory.BeanCreationException:Error creating bean with name 'dataCacheManager': Injection of resource dependencies failed; nested exception is org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'workTypeServiceManager' is expected to be of type 'com.xxx.mapper.WorkTypeMapper'but was actually of type 'com.xxx.manager.WorkTypeServiceManager$$EnhancerBySpringCGLIB$$30dd8c09'at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:596)at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:90)at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:374)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1395)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:592)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515)at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$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.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:849)at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:877)at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:549)at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:142)at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:775)at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397)at org.springframework.boot.SpringApplication.run(SpringApplication.java:316)at org.springframework.boot.SpringApplication.run(SpringApplication.java:1260)at org.springframework.boot.SpringApplication.run(SpringApplication.java:1248)at com.xxx.ServerApplication.main(ServerApplication.java:41)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:498)at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:48)at org.springframework.boot.loader.Launcher.launch(Launcher.java:87)at org.springframework.boot.loader.Launcher.launch(Launcher.java:50)at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:51)
Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'taskApplyManager': Unsatisfied dependencyexpressed through field 'dataCacheManager'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataCacheManager': Injection of resource dependencies failed; nested exception is org.springframework.beans.factory.BeanNotOfRequiredTypeException:Bean named 'workTypeServiceManager' is expected to be of type 'com.xxx.mapper.WorkTypeMapper' but was actually of type 'com.xxx.manager.WorkTypeServiceManager$$EnhancerBySpringCGLIB$$30dd8c09'at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:596)at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:90)at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:374)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1395)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:592)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515)at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$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)... 27 common frames omitted
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataCacheManager': Injection of resource dependencies failed; nested exception is org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'workTypeServiceManager' is expected to be of type 'com.xxx.mapper.WorkTypeMapper' but was actually of type 'com.xxx.manager.WorkTypeServiceManager$$EnhancerBySpringCGLIB$$30dd8c09'at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessProperties(CommonAnnotationBeanPostProcessor.java:324)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1395)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)... 40 common frames omitted
Caused by: org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'workTypeServiceManager' is expected to be of type 'com.xxx.mapper.WorkTypeMapper' but was actually of type 'com.xxx.manager.WorkTypeServiceManager$$EnhancerBySpringCGLIB$$30dd8c09'at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:392)at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:204)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.resolveBeanByName(AbstractAutowireCapableBeanFactory.java:452)at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.autowireResource(CommonAnnotationBeanPostProcessor.java:526)at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.getResource(CommonAnnotationBeanPostProcessor.java:496)at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor$ResourceElement.getResourceToInject(CommonAnnotationBeanPostProcessor.java:636)at org.springframework.beans.factory.annotation.InjectionMetadata$InjectedElement.inject(InjectionMetadata.java:180)at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:90)at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessProperties(CommonAnnotationBeanPostProcessor.java:321)... 51 common frames omitted
是为记。
