JPA实现“一对一”映射

矫情吗；* 2021-07-24 18:41 379阅读 0赞

**一 代码位置**

[https://gitee.com/cakin24/code/tree/master/08/JpaOneToOneDemo][https_gitee.com_cakin24_code_tree_master_08_JpaOneToOneDemo]

**二 关键代码**

1 Student

package com.example.demo.entity;
    
    import lombok.Data;
    import javax.persistence.*;
    
    @Entity
    @Data
    @Table(name = "stdu")
    public class Student {
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        private long id;
        private String name;
        @Column(columnDefinition = "enum('male','female')")
        private String sex;
        /**
         * Description:
         * 建立集合，指定关系是一对一，并且申明它在cart类中的名称
         * 关联的表为card表，其主键是id
         * 指定外键名为card_id
         */
        @OneToOne(cascade = CascadeType.ALL)
        @JoinColumn(name = "card_id")
        private Card card;
    }

2 Card

package com.example.demo.entity;
    
    import lombok.Data;
    import javax.persistence.*;
    
    @Entity
    @Table(name = "card")
    @Data
    public class Card {
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        private long id;
        private Integer num;
    }

3 测试代码

package com.example.demo.entity;
    
    import com.example.demo.repository.CardRepository;
    import com.example.demo.repository.StudentRepository;
    import org.junit.Test;
    import org.junit.runner.RunWith;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.test.context.SpringBootTest;
    import org.springframework.test.context.junit4.SpringRunner;
    import static org.junit.Assert.*;
    
    @SpringBootTest
    @RunWith(SpringRunner.class)
    public class oneToOneTest {
        @Autowired
        private StudentRepository studentRepository;
        @Autowired
        private CardRepository cardRepository;
    
        @Test
        public void testOneToOne() {
            Student student1 = new Student();
            student1.setName("赵大伟");
            student1.setSex("male");
            Student student2 = new Student();
            student2.setName("赵大宝");
            student2.setSex("male");
    
            Card card1 = new Card();
            card1.setNum(422802);
            student1.setCard(card1);
            studentRepository.save(student1);
            studentRepository.save(student2);
            Card card2 = new Card();
            card2.setNum(422803);
            cardRepository.save(card2);
            /**
             * Description: 获取添加之后的id
             */
            Long id = student1.getId();
            /**
             * Description: 删除刚刚添加的student1
             */
            studentRepository.deleteById(id);
        }
    }

**三 控制台打印**

Hibernate: insert into card (num) values (?)
    Hibernate: insert into stdu (card_id, name, sex) values (?, ?, ?)
    Hibernate: insert into stdu (card_id, name, sex) values (?, ?, ?)
    Hibernate: insert into card (num) values (?)
    Hibernate: select student0_.id as id1_1_0_, student0_.card_id as card_id4_1_0_, student0_.name as name2_1_0_, student0_.sex as sex3_1_0_, card1_.id as id1_0_1_, card1_.num as num2_0_1_ from stdu student0_ left outer join card card1_ on student0_.card_id=card1_.id where student0_.id=?
    Hibernate: delete from stdu where id=?
    Hibernate: delete from card where id=?

**四 数据库数据如下**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70][]

[https_gitee.com_cakin24_code_tree_master_08_JpaOneToOneDemo]: https://gitee.com/cakin24/code/tree/master/08/JpaOneToOneDemo
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70]: /images/20210724/ce10494fdcc047da8b2cd846efd3f41a.png