java - Spring Boot JPA ManyToMany MappingException

Question

我有两个实体想要通过 ManyToMany 关联。我找到了很多示例(例如 https://en.wikibooks.org/wiki/Java_Persistence/ManyToMany#Example_of_a_ManyToMany_relationship_annotation 或 https://vladmihalcea.com/the-best-way-to-use-the-manytomany-annotation-with-jpa-and-hibernate/ )，甚至在我的代码中还有另一个地方，多对多关系似乎起作用，但到目前为止我仍然无法弄清楚这个。

我遇到以下异常:

Caused by: org.hibernate.MappingException: Foreign key (FKru66hm0369ayn8dvjj2rgxr9v:user_role [role_id])) must have same number of columns as the referenced primary key (user_role [user_id,role_id])

类用户

@Entity
@Table(name = "user")
public class User {

    @Id
    @GeneratedValue
    @Column(name = "user_id")
    private long id;

    @ManyToMany
    @JoinTable(
        name = "user_role",
        joinColumns = @JoinColumn(name = "user_id"),
        inverseJoinColumns = @JoinColumn(name = "role_id"))
    private Set<Role> roles;

    // getters and setters
}

类(class)角色

@Entity
@Table(name = "user_role")
public class Role {

    @Id
    @GeneratedValue
    @Column(name = "role_id")
    private long id;

    @ManyToMany(mappedBy = "roles")
    private Set<User> users;

    // getters and setters

}

Answer 1

检查this link !

无论如何，问题是你拥有类(class)角色

@Entity
@Table(name = "user_role")
public class Role {

也在用户类中

 @JoinTable(
        name = "user_role",
        joinColumns = @JoinColumn(name = "user_id"),
        inverseJoinColumns = @JoinColumn(name = "role_id"))

两个地方， table 的名称是相同的......
这一定是错误的原因......