受弹簧数据的启发，我想创建一个抽象的RESTController，可以将其扩展到很多控制器上。我创建了以下类：

@Controller
public abstract class RESTController<E, PK extends Serializable, R extends PagingAndSortingRepository<E, PK>>
{
    @Autowired
    private R repository;

    @RequestMapping(method=RequestMethod.GET, params={"id"})
    @ResponseBody 
    public E getEntity(@RequestParam PK id)
    {
        return repository.findOne(id);
    }

    ...
}

我希望泛型将允许我在存储库中使用@Autowired，但出现以下错误：

SEVERE: Allocate exception for servlet appServlet
org.springframework.beans.factory.NoSuchBeanDefinitionException: No unique bean of type [org.springframework.data.repository.PagingAndSortingRepository] is defined: expected single matching bean but found 3: [groupRepository, externalCourseRepository, managedCourseRepository]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:800)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:707)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:478)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:284)
    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)

我知道错误告诉我，@ Autowired有多个匹配项。我很困惑，因为我认为通过创建以下控制器它会起作用：

@Controller
@RequestMapping(value="/managedCourse")
public class ManagedCourseController extends RESTController<ManagedCourse, Long, ManagedCourseRepository>
{
    ...
}

通过在RESTController中使用如下方法可以轻松解决此问题：

protected abstract R getRepository();

然后在实现类中执行此操作：

@Autowired
private ManagedCourseRepository repository;

@Override
protected ManagedCourseRepository getRepository() 
{
    return repository;
}

我只是想知道是否有人对我如何使它起作用有任何想法。

我也发现了这个有趣的伯爵。