@Autowired失败-java.lang.ClassCastException

Question

I am using java config to configure my Beans:

   @Configuration
public class SpringJavaConfig { 
    @Bean
    public IBrandsApi getBrandsApi(){
        return new BrandsApi();
    }
}

I can see in debug mode while loading that spring aware to the SpringJavaConfig.

In my controller I am using the autowire:

@Controller
@RequestMapping("/api/brands")
public class BrandsController extends BaseController {

BrandsApi brandsApi;

@Autowired
public void setBrandsApi(IBrandsApi brandsApi){
    this.brandsApi = (BrandsApi)brandsApi;
}

}

this is the brands API decleration:

@Transactional
public  class BrandsApi extends BaseApplicationAPI<Object> implements IBrandsApi {

    public BrandsApi(){

    }
}
@Transactional
public interface IBrandsApi {}

this is the exception that i get while loading the tomcat:

 Mar 9, 2011 9:50:54 AM org.apache.catalina.core.StandardContext listenerStart
SEVERE: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'brandsController': Injection of autowired dependencies failed; nested exception is java.lang.ClassCastException: $Proxy46 cannot be cast to com.affiliates.BrandsApi
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:285)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1074)
    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:291)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:288)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:190)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:580)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:895)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:425)
    at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:276)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:197)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:47)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4521)
    at org.apache.catalina.core.StandardContext$1.call(StandardContext.java:5004)
    at org.apache.catalina.core.StandardContext$1.call(StandardContext.java:4999)
    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
    at java.util.concurrent.FutureTask.run(FutureTask.java:166)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:636)
Caused by: java.lang.ClassCastException: $Proxy46 cannot be cast to com.affiliates.BrandsApi
    at com.affiliates.controllers.BrandsController.setBrandsApi(BrandsController.java:37)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:616)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredMethodElement.inject(AutowiredAnnotationBeanPostProcessor.java:582)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:84)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:282)
    ... 21 more

Answer 1

See this question: Application context bean .

Why are you downcasting your service to BrandsApi ? Shouldn't you be working with interface only?

Answer 2

Does your BrandsApi use @Transactional or any other kind of AOP? Maybe the problem is you're using a concrete class and not a interface as reference and that could lead a problem when Spring creates some kind of AOP Proxy class.

Check this related question: Spring Autowiring class vs. interface?