Question

我有两个具有多对一关系的表，但它们没有外键。就像Student很多，而Teacher就是那个，

实体例如：

@Entity
@Table(name = "student")
class Student {


   @Column(name = "TeacherName")
   private String teacherName;

   @ManyToOne
   private Teacher teacher
}


@Entity
@Table(name = "teacher")
class Teacher {

 private String name;
}

当我查询学生时，sql是：

select * from Student as st INNER JOIN Teacher as tcr ON st.TeacherName = tcr.name;

我发现@ManyToOne无法正常工作，看起来它需要一个外键。该表不能提供这样的。

有人可以告诉我如何配置实体吗？

Answer 1

您必须使用以下映射：

public class Teacher  {

    @OneToMany(mappedBy = "teacher")
    private Set<Student> students;

    @Column(name = "name")
    private String name;
}

public class Student {
    @ManyToOne
    @JoinColumn(name = "teacherName", referencedColumnName = "name")
    private Teacher teacher;

}

然后在HQL中：

select s from Student s INNER JOIN s.teacher t where t.name = :name

<强>替代地如果你想继续使用当前的映射，那么你需要在hql中使用'旧'连接样式来实现非外键列的连接：

select s from Student s, Teacher t where t.name = s.teacherName and t.name = :name

如何弹出jpa hibernate创建具有多对一但没有外键的实体

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