Hibernate 由复合键映射

Question

我想在@OneToMany 中使用映射，但它会引发异常

org.hibernate.MappingException: Unable to read the mapped by attribute for moduleRoles in org.caau.entity.UserModuleRole!

这是我的实体映射。UserModuleRole是复合类。如果使用注释代码，程序是正确的。有人帮我解决吗？

@Entity
@Table(name = "user")
public class User{
    private long id;
    private Set<UserModuleRole> moduleRoles;

    @Id
    @Column(name = "id", nullable = false)
    @GeneratedValue(strategy = GenerationType.AUTO)
    public long getId() {
        return id;
    }

    @OneToMany(fetch = FetchType.EAGER,mappedBy="user")
    //if use under code,program is correct,but i want to use mappedBy!
    //@OneToMany(fetch = FetchType.EAGER)
    //@JoinColumn(name = "user_id")
    public Set<UserModuleRole> getModuleRoles() {
        return moduleRoles;
    }

}

这里是 UserModuleRole 类

 @Entity
    @Table(name = "user_module_role")
    @IdClass(UserModuleRolePK.class)
        public class UserModuleRole{
        private User user;
        private ModuleRole moduleRole;
        private long addUserId;
        private Date addDate;
        private long updateUserId;
        private Date updateDate;

        @Id
        public User getUser() {
            return user;
        }

        @Id
        public ModuleRole getModuleRole() {
            return moduleRole;
        }
    }
    class UserModuleRolePK implements Serializable {

        private static final long serialVersionUID = -9132981262254922539L;

        private User user;
        private ModuleRole moduleRole;

        @ManyToOne
        @JoinColumn(name = "user_id", nullable = false)
        public User getUser() {
            return user;
        }

        @ManyToOne
        @JoinColumns({ @JoinColumn(name = "module_id", nullable = false), @JoinColumn(name = "role_id", nullable = false) })
        public ModuleRole getModuleRole() {
            return moduleRole;
        }
    }
    }

Answer 1

首先，您遇到的异常是由于您的 UserModuleRole 类中没有任何名为 user 的关系属性。

您要实现的是您的实体User 和ModuleRole 之间的多对多 关系，在您的示例中不需要中间类UserModuleRole 作为唯一的它拥有的字段/属性是对其他两个实体的外键引用。

除非您忘记在问题中添加更多信息，否则您应该使用的映射要简单得多，如下所示：

@Entity
public class ModuleRole {

    private Long id;

    private Set<User> users;

    @Id
    @Column(name = "id")
    public Long getId() {
        return id;
    }

    @ManyToMany
    @JoinTable(name = "user_module_role", 
        joinColumns = @JoinColumn(name = "module_id", referencedColumnName = "id"),
        inverseJoinColumns = @JoinColumn(name = "user_id"), referencedColumnName = "id")
    public Set<Users> getUsers() {
        return users;
    }

}

@Entity
@Table(name = "user")
public class User{
    private Long id;
    private Set<ModuleRole> moduleRoles;

    @Id
    @Column(name = "id", nullable = false)
    @GeneratedValue(strategy = GenerationType.AUTO)
    public long getId() {
        return id;
    }

    @ManyToMany(mappedBy = "users")
    public Set<ModuleRole> getModuleRoles() {
        return moduleRoles;
    }

}

Hibernate 将自行处理中间表，除非您想向关系中添加其他字段，否则您不必担心它，在这种情况下 this tutorial 会有所帮助。