在泛型超类中自动关联泛型组件

Question

我在Spring 4.0（使用Spring Boot）环境中遇到以下情况：

映射界面：

public interface EntityModelMapper<ENTITY extends AbstractEntity, MODEL extends AbstractModel>{ }

映射实现：

@Component
public class ProductEntityModelMapper implements EntityModelMapper<Product, ProductModel>{ }

服务：

public interface CrudService<MODEL extends AbstractModel>{ }

我想做这样一个抽象的超类服务：

public abstract AbstractCrudService<ENTITY extends AbstractEntity, MODEL extends AbstractModel> implements CrudService<MODEL>{

@Autowired
private EntityModelMapper<ENTITY, MODEL> mapper;

  public EntityModelMapper<ENTITY, MODEL> getMapper(){ 
      return mapper; 
  }
}

所以我可以有如下实现：

@Service
public ProductCrudService extends AbstractCrudService<Product, ProductModel>{

  public void someMethod(Product product){
    ProductModel model = getMapper().map(product);
  }

}

但是Spring告诉我它找不到EntityModelMapper的合格bean来注入服务类。这种情况是可能的，我做错了什么，还是我在挑战Spring依赖注入的极限？

堆栈跟踪：

org.springframework.beans.factory.BeanCreationException:
 Error creating bean with name 'productCrudService':
 Injection of autowired dependencies failed;
 nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field:
 private com.flycatcher.seagull.mapper.EntityModelMapper 
com.flycatcher.seagull.facade.service.crud.AbstractCrudService.mapper;
 nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException:
 No qualifying bean of type [com.flycatcher.seagull.mapper.EntityModelMapper] 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)}

Answer 1

据此：https://spring.io/blog/2013/12/03/spring-framework-4-0-and-java-generics从Spring 4.0版本开始是可能的。

这对我也没用。（使用4.2.3时出现相同的异常和Im）。因此，请尝试升级到最新版本4.2.6。

如果仍然不起作用，您可以使用@Qualifier注释和autowire EntityModelMapper作为子类中的接口，并将getMapper定义为抽象：

  @Component
  @Qualifier("productEntityModelQualifier")
  public class ProductEntityModelMapper implements EntityModelMapper<Product, ProductModel>{ }

然后在ProductCrudService中：

@Service
public ProductCrudService extends AbstractCrudService<Product, ProductModel>{

  @Autowired
  @Qualifier("productEntityModelQualifier")
  EntityModelMapper<Product, ProductModel> mapper;

  @Override
  protected EntityModelMapper<Product, ProductModel> getMapper(){return mapper;}

  public void someMethod(Product product){
    ProductModel model = getMapper().map(product);
  }

}