使用 Spring Data JPA 的多对多映射和保存问题

Question

我有一个数据库模式，我必须在其中映射多对多关系

***** Tables **********

person
--------
id - int 
name - varchar

color
-------------
id - int 
color - varchar

person_color
------------
person_id - int (matches an id from person)
color_id - int (matches an id from color)

我已将上述场景转换为 JPA @Entities 作为

@Entity
public class Person {


    @Id
    @GeneratedValue
    private Integer id;

    private String name;

    @ManyToMany(cascade = {CascadeType.ALL})
    private List<Color> colors;
   /// setters getters are there
}

和

@Entity
public class Color {


    @Id
    @GeneratedValue
    private Integer id;

    private String color;

    @ManyToMany(cascade = {CascadeType.ALL})
    private List<Person> person;
   /// setters getters are there
}

上面的代码创建了四个表

person
person_color
color
color_person

但我只想要三张桌子

 person
    person_color
    color

上面的代码有什么问题，想要将数据保存到数据库的示例任何资源或链接到使用 JPA 多对多关系保存数据的好示例。

Answer 1

将您的 Person 类更新为以下

@Entity
public class Person {


    @Id
    @GeneratedValue
    private Integer id;

    private String name;

    @ManyToMany(targetEntity = Color.class, cascade = {CascadeType.ALL})
    @JoinTable(name = "person_color", joinColumns = { @JoinColumn(name = "person_id") }, 
                       inverseJoinColumns = { @JoinColumn(name = "color_id") })
    private List<Color> colors;
   /// setters getters are there
}

将您的颜色类更新为以下

@Entity
public class Color {


    @Id
    @GeneratedValue
    private Integer id;

    private String color;

    @ManyToMany(mappedBy = "colors", cascade = CascadeType.ALL)
    private List<Person> persons;
   /// setters getters are there
}