Question

我的Parent课程有两个子课程：Child和ParentHobby。 Child类具有单个PK，并且@OneToMany映射有效。问题是我不知道如何在ParentHobby类上映射它，它具有复合PK。

父：

//this works
@OneToMany(cascade = CascadeType.ALL, mappedBy = "parent", fetch = FetchType.EAGER)
private List<Child> childList;

//this DOES NOT work
@OneToMany(cascade = CascadeType.ALL, mappedBy = "parent", fetch = FetchType.EAGER)
private List<ParentHobby> hobbyList;

儿童：

@Entity
@Table(name="CHILD")
public class Child {


    @Id
    @SequenceGenerator(name="CHILD_SEQ", sequenceName="CHILD_DB_SEQ", allocationSize = 1)
    @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="CHILD_SEQ")
    @Column(name="CHILD_ID")
    private long childID;

    @JoinColumn(name = "PARENT_ID", referencedColumnName = "PARENT_ID", insertable = true, updatable = true)
    @ManyToOne(optional = true)
    private Parent parent;

ParentHobby：

@Entity @table（名称= “PARENT_HOBBY”）公共课ParentHobby {

@EmbeddedId
private ParentHobbyPK id;

ParentHobbyPK：

@Embeddable
public class ParentHobbyPK {

    @JoinColumn(name = "PARENT_ID", referencedColumnName = "PARENT_ID", insertable = true, updatable = true)
    @ManyToOne(optional = true)
    private Parent parent;

    @Column(name="HOBBY_ID")
    private String hobbyID;

我在编译时获得的异常是：

mappedBy reference an unknown target entity property: ParentHobby.parent in Parent.hobbyList

当子项具有复合主键时，如何在父实体中定义@OneToMany关系？

<子>类似：

@OneToMany relationship with Composite key

Hibernate Entity mapping when Foreign key is part of the composite primary key?

JPA composite key @OneToMany

Answer 1

您需要使用派生身份。

ParentHobbyPK应如下所示：

@Embeddable
public class ParentHobbyPK {
    @Column(name="HOBBY_ID")
    private String hobbyID;
    private long parentID; // corresponds to the PK type of Parent
}

ParentHobby应该看起来像这样（重要的是@MapsId注释）：

@Entity
@Table(name="PARENT_HOBBY")
public class ParentHobby {
    @EmbeddedId
    private ParentHobbyPK id;

    @MapsId("parentID") // maps parentID attribute of the embedded ID
    @ManyToOne(optional = true)
    @JoinColumn(name = "PARENT_ID", referencedColumnName = "PARENT_ID", insertable = true, updatable = true)
    private Parent parent;

    ...
}

JPA 2.1规范第2.4.1节讨论了派生身份。

当孩子有复合PK时，如何在父实体中定义@OneToMany？

1 个答案: