Spring 将实体传递给超级 class

Question

我创建了这样的通用超级class：

@Repository
public class RootQueryCreator<T> {

   @PersistenceContext
   private EntityManager em;

   private T entity;
   CriteriaBuilder criteriaBuilder = null;
   CriteriaQuery<T> criteriaQuery = null;
   Root<T> rootTable = null;

   public RootQueryCreator() {}

   public RootQueryCreator(T entity) {
    super();
    this.entity = entity;
   }

   @PostConstruct
   public void initRootQuery() {
    criteriaBuilder = em.getCriteriaBuilder();
    criteriaQuery = (CriteriaQuery<T>) 
    criteriaBuilder.createQuery(this.entity.getClass());        
    rootTable = (Root<T>) criteriaQuery.from(entity.getClass());
}}

这个 superclass 将被实体中的每个 DAOImpl-Class 使用。像这样：

@Repository
@Qualifier("myEntitiyClass")
public class MyEntityDAOImpl  extends 
RootQueryCreator<MyEntity> { 

@Autowired
public MyEntityDAOImpl() {
    super(new MyEntity()); //pass any Entity for the Root-Class from Criteria-Framework
}

@Override
public List<MyEntity> getAll() throws Exception {
    super.getCriteriaQuery().select(super.rootTable);
    return super.getEm().createQuery(criteriaQuery).getResultList();
}

public List<MyEntity> retrieveData(){

}}

并且每个 DAOImpl-Class 将被自动连接到一些服务-class 中，如下所示：

@Service
public class myLecture {

@Autowired
@Qualifier("myEntitiyClass")
private JpaRepositority<MyEntityDAOImpl> myEntityDAOImpl;

public void retrieveData(){

     myEntityDAOImpl.retrieveData();
} }

最后我得到这个错误：

IllegalStateException: Autowired annotation requires at least one argument: MyEntityDAOImpl()

实际上我不需要将任何实体传递给 DAOImpl-Class。我该怎么办？

Answer 1

Autowired 注释指定：

Marks a constructor, field, setter method or config method as to be autowired by Spring's dependency injection facilities.

但是你用 @Autowired 注释了构造函数而没有提供任何依赖项作为参数:

@Autowired
public MyEntityDAOImpl() { //-> Empty arg is the issue here
    super(new MyEntity()); //pass any Entity for the Root-Class from Criteria-Framework
}

而例外情况：

IllegalStateException: Autowired annotation requires at least one argument: MyEntityDAOImpl()

事实上，您不需要在 MyEntityDAOImpl 中自动装配任何内容，因为它不需要在其构造函数中有任何依赖关系。所以只需删除注释并让 Spring 将构造函数作为普通构造函数调用：

public MyEntityDAOImpl() {
    super(new MyEntity()); //pass any Entity for the Root-Class from Criteria-Framework
}

Spring 将实体传递给超级 class

Spring pass entity to super class

spring

autowired

jpa-2.0