复合外键 JPA TypeMismatchException

Question

我已经通过简单的 Parent Child tables 解释了我的场景。

我的复合主键也是一个复合外键引用父table。

create table parent(
code varchar(10) not null,
id int not null,
parentcol varchar(10),
primary key(code,id)
);

create table child(
code varchar(10) not null,
id int not null,
childcol varchar(10) not null,
primary key(code, id),
foreign key(code, id) references parent(code,id)
);

创建的实体（这是通过 Eclipse JPA 插件）

@Entity
@Table(name="parent")
@NamedQuery(name="Parent.findAll", query="SELECT p FROM Parent p")
public class Parent implements Serializable {
private static final long serialVersionUID = 1L;

@EmbeddedId
private ParentPK id;

@Column(length=10)
private String parentcol;

//bi-directional one-to-one association to Child
@OneToOne(mappedBy="parent")
private Child child;

public Parent() {
}

/* getters and setters */

}

@Embeddable
public class ParentPK implements Serializable {
//default serial version id, required for serializable classes.
private static final long serialVersionUID = 1L;

@Column(unique=true, nullable=false, length=10)
private String code;

@Column(unique=true, nullable=false)
private int id;

    /* getters and setters */

/** Overridden equals and hashcode **/
}



@Entity
@Table(name="child")
@NamedQuery(name="Child.findAll", query="SELECT c FROM Child c")
public class Child implements Serializable {
private static final long serialVersionUID = 1L;

@EmbeddedId
private ChildPK id;

@Column(nullable=false, length=10)
private String childcol;

//bi-directional one-to-one association to Parent
@OneToOne
@JoinColumns({
    @JoinColumn(name="code", referencedColumnName="code", nullable=false, insertable=false, updatable=false),
    @JoinColumn(name="id", referencedColumnName="id", nullable=false, insertable=false, updatable=false)
    })
private Parent parent;

    /* getters and setters */

}

@Embeddable
public class ChildPK implements Serializable {
//default serial version id, required for serializable classes.
private static final long serialVersionUID = 1L;

@Column(insertable=false, updatable=false, unique=true, nullable=false, length=10)
private String code;

@Column(insertable=false, updatable=false, unique=true, nullable=false)
private int id;

/* overridden equals and hashcode */

我正在使用 Spring 数据来保存我的实体，如下所示。 Parent table 包含一条代码为 "code" 且 Id 为 1.

的记录

Child child = new Child();
ChildPK childPK = new ChildPK();
childPK.setCode("code");
childPK.setId(1);
child.setId(childPK);
child.setChildcol("child1");
childRepository.save(child);

当必须插入新记录时，第一个运行成功。但问题是在 2 日运行必须更新时，让我们说，

child.setChildcol("child2");

我遇到错误

HHH000327: Error performing load command : org.hibernate.TypeMismatchException: Provided id of the wrong type for class com.xebia.eTechLog.entities.Parent. Expected: class com.xebia.eTechLog.entities.ParentPK, got class com.xebia.eTechLog.entities.ChildPK

以防我尝试在子 table 中提供 ParentPk 的参考

@Entity
@Table(name="child")
@NamedQuery(name="Child.findAll", query="SELECT c FROM Child c")
public class Child implements Serializable {
private static final long serialVersionUID = 1L;

@EmbeddedId
private ParentPK id;

@Column(nullable=false, length=10)
private String childcol;

//bi-directional one-to-one association to Parent
@OneToOne
@JoinColumns({
    @JoinColumn(name="code", referencedColumnName="code", nullable=false, insertable=false, updatable=false),
    @JoinColumn(name="id", referencedColumnName="id", nullable=false, insertable=false, updatable=false)
    })
private Parent parent;

它确实有效，但如果父级中有更多字段，它就不会了 class，这是我的真实情况。

Answer 1

您应该使用派生身份。这意味着您应该指出子项对其父项的引用映射了子项的 ID（使用 @MapsId 注释）：

@Entity
public class Child implements Serializable {
    @EmbeddedId
    private ChildPK id;

    @Column(nullable=false, length=10)
    private String childcol;

    @OneToOne
    @MapsId  // <<< NB
    @JoinColumns({
        @JoinColumn(name="code", referencedColumnName="code"),
        @JoinColumn(name="id", referencedColumnName="id")
    })
    private Parent parent;

    ...
}

派生身份在 JPA 2.1 规范的第 2.4.1 节中进行了讨论。

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