Springboot + MySQL+ JPA Ⅵ 多表关联

蔚落 2023-10-02 15:55 34阅读 0赞

JPA可以使用注解进行多表关联

#### **一、多对一 @ManyToOne**  ####

User表

@Data
    @Entity
    @JsonIgnoreProperties({"hibernateLazyInitializer","handler"})
    public class User {
    
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        private Integer id;
    
        private String name;
    
        private Integer age;
        
        @ManyToOne
        @JoinColumn(name="work_id") //work_id是user表中的外键
        private Work work;  //work是user表的关联表
    }

Work表

@Data
    @Entity
    @JsonIgnoreProperties({"hibernateLazyInitializer","handler"})
    public class Work {
    
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        private Integer id;
    
        private String name;
    }

service层（还是使用自带的save方法）

@Transactional
    public User save(User user){
    	return userDao.save(user);
    }

control层

/**
     * 单条数据添加
     * @param id
     * @param name
     * @param age
     * @param work_id user的外键，也是work的id
     * @return 返回添加的user数据
     */
    @GetMapping("/save")
    public User save(Integer id,String name, Integer age,Integer work_id){
    	User user = new User();
    	Work work = new Work();
    	user.setId(id);
    	user.setName(name);
    	user.setAge(age);
    	work.setId(work_id);
        user.setWork(work);
    	return userService.save(user);
    }

测试成功！

![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA6Iul5Y2a6LGG_size_20_color_FFFFFF_t_70_g_se_x_16][]

![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA6Iul5Y2a6LGG_size_20_color_FFFFFF_t_70_g_se_x_16 1][]

总共进行了三条jpql语句

![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA6Iul5Y2a6LGG_size_20_color_FFFFFF_t_70_g_se_x_16 2][]

[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA6Iul5Y2a6LGG_size_20_color_FFFFFF_t_70_g_se_x_16]: https://img-blog.csdnimg.cn/a3dd16d161f14ddb9e292a280551973e.png?x-oss-process=image/watermark,type_ZHJvaWRzYW5zZmFsbGJhY2s,shadow_50,text_Q1NETiBA6Iul5Y2a6LGG,size_20,color_FFFFFF,t_70,g_se,x_16
[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA6Iul5Y2a6LGG_size_20_color_FFFFFF_t_70_g_se_x_16 1]: https://img-blog.csdnimg.cn/48329675a9bc4b2db4246deb348a44c7.png?x-oss-process=image/watermark,type_ZHJvaWRzYW5zZmFsbGJhY2s,shadow_50,text_Q1NETiBA6Iul5Y2a6LGG,size_20,color_FFFFFF,t_70,g_se,x_16
[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA6Iul5Y2a6LGG_size_20_color_FFFFFF_t_70_g_se_x_16 2]: https://img-blog.csdnimg.cn/e65591f002da44bd894d0476e776910f.png?x-oss-process=image/watermark,type_ZHJvaWRzYW5zZmFsbGJhY2s,shadow_50,text_Q1NETiBA6Iul5Y2a6LGG,size_20,color_FFFFFF,t_70,g_se,x_16