hibernate多对多双向关联

老师可以查看自己的学生，学生也可以查看自己的老师：

老师Teacher类：

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;
    }
    /**
     *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;
    }
    
    
    
}

Student类：

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.ManyToMany;

@Entity
public class Student {

    private int id;
    private String name;
    private Set<Teacher>  teachers = new HashSet<Teacher>();
    
    //
    @ManyToMany(mappedBy="students")
    public Set<Teacher> getTeachers() {
        return teachers;
    }
    public void setTeachers(Set<Teacher> teachers) {
        this.teachers = teachers;
    }
    @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;
    }
    
    
    
    
}

生成的表和多对一单向一样：

生成表语句：

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)

 

 欢迎关注个人公众号一起交流学习：