hibernate多对多单向关联

多对多单向，一个学生可以有多个老师，一个老师也可以教多个学生。老师可以找到他的学生，学生找不到教他的老师。

老师类Teacher：

package com.oracle.hibernate;

import java.util.HashSet;

import java.util.Set;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.JoinColumn;

import javax.persistence.JoinColumns;

import javax.persistence.JoinTable;

import javax.persistence.ManyToMany;

import javax.persistence.OneToMany;

import javax.persistence.OneToOne;

import javax.persistence.Table;

@Entity

public class Teacher {

    private int id;

    private String name;

    //用set集合，不重复。因为表里的记录也不会重复

    private Set<Student>  students = new HashSet<Student>();

    @Id

    @GeneratedValue

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    /**

     * 多对多单向，会生成一张中间表，默认名字为Teacher_student，

     * 默认的列名为teacher_id，students_id，

     *    @JoinTable修改中间表名、属性名

     *    name="t_s" 指定中间表名字

     *    中间表只有学生id和老师id，

     *    joinColumns指定当前（Teacher类）的表的id

     *    inverseJoinColumns，逆转的，对方的，指定对方那张表对应的外键的id

     */

    @ManyToMany

    @JoinTable(name="t_s",

            joinColumns={@JoinColumn(name="teacher_id")},

            inverseJoinColumns={@JoinColumn(name="student_id")}

            )

    public Set<Student> getStudents() {

        return students;

    }

    public void setStudents(Set<Student> students) {

        this.students = students;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

}

学生类Student：

package com.oracle.hibernate;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.JoinColumn;

import javax.persistence.ManyToOne;

@Entity

public class Student {

    private int id;

    private String name;

    @Id

    @GeneratedValue

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

}

生成的表：

hibernate生成表的语句：

create table Student (
id integer not null auto_increment,
name varchar(255),
primary key (id)
)

create table Teacher (
id integer not null auto_increment,
name varchar(255),
primary key (id)
)

create table t_s (
teacher_id integer not null,
student_id integer not null,
primary key (teacher_id, student_id)
)

alter table t_s
add index FK1BF68372EF01B (teacher_id),
add constraint FK1BF68372EF01B
foreign key (teacher_id)
references Teacher (id)

alter table t_s
add index FK1BF682693A57B (student_id),
add constraint FK1BF682693A57B
foreign key (student_id)
references Student (id)

生成了Student表和Teacher表和中间表 t_s，列名也和自己设置的一样。

巴特西

hibernate多对多单向关联

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