使用JPA一对一关系

本文介绍了使用JPA一对一关系的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我已经使用JPA创建了两个表。我需要给这些表之间1-1关系。谁能告诉我如何在这些表之间建立关系。

I have created two table using JPA. i need to give 1-1 relationship between these tables. Can any one tell me how to give relationship between these tables.

推荐答案

只需在表中拥有该关系的列有FK约束。例如：

Simply add a column in the table "owning" the relation with a FK constraint. For example:

CREATE TABLE MYENTITYA ( ID BIGINT NOT NULL, MYENTITYB_ID BIGINT ); CREATE TABLE MYENTITYB ( ID BIGINT NOT NULL ); ALTER TABLE MYENTITYA ADD CONSTRAINT SQL100326144838300 PRIMARY KEY (ID); ALTER TABLE MYENTITYB ADD CONSTRAINT SQL100326144838430 PRIMARY KEY (ID); ALTER TABLE MYENTITYA ADD CONSTRAINT FKB65AC952578E2EA3 FOREIGN KEY (MYENTITYB_ID) REFERENCES MYENTITYB (ID);

将被这样映射：

@Entity public class MyEntityA implements Serializable { private Long id; private MyEntityB myEntityB; @Id @GeneratedValue public Long getId() { return this.id; } @OneToOne(optional = true, cascade = CascadeType.ALL) public MyEntityB getEntityB() { return this.myEntityB; } //... } @Entity public class MyEntityB implements Serializable { private Long id; @Id @GeneratedValue public Long getId() { return id; } //... }

如果 EntityA 和 EntityB 之间的关系不是可选的，则添加 NOT NULL 约束。

If the relation between EntityA and EntityB is not optional, then add a NOT NULL constraint.