java - 使用 JpaRepository 进行内连接，无需编写查询

Question

我有某些实体(我已通过 Hibernate 链接)，我想从数据库中查询它们；无需显式写出查询。

MyParent.java

@Entity
@Table(name="myparent")
public class MyParent {

    @Id
    @SequenceGenerator(name = "myparent_id_seq", sequenceName = "myparent_id_seq", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "myparent_id_seq")
    private Long id;

    @OneToOne(mappedBy = "myParent", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    private MyChild myChild;

    public void linkChild(MyChild myChild) {
        this.myChild = myChild;
        myChild.setParent(this);
    }

    // rest of code

}

MyChild.java

@Entity
@Table(name="myChild")
public class MyChild {

    @Id
    @SequenceGenerator(name = "mychild_id_seq", sequenceName = "mychild_id_seq", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "mychild_id_seq")
    private Long id;

    @OneToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "myparent_id")
    private MyParent myParent;

    // rest of code

}

现在，我想做:

select * from myparent p 
inner join mychild c on p.id = c.myparent_id;

-- basically I want to get all instances of MyParent where MyChild is not null

什么会返回一个 MyParent 的实例，然后我可以使用我的 getter 和 setter 来解析它。我在网上找到的所有内容都是明确写出查询。

有什么办法可以做到这一点吗？

Answer 1

您可以使用jpql:

@Query("select mp from MyParent mp where mp.myChild is not null")

或者您可以使用 native 查询

@Query(value = "select p.* from myparent p inner join mychild c on p.id = c.myparent_id", nativeQuery = true)