Hibernate基于注解annotation的配置

Annotation在框架中是越来越受欢迎了，因为annotation的配置比起XML的配置来说方便了很多，不需要大量的XML来书写，方便简单了很多，只要几个annotation的配置，就可以完成我们以前需要书写的大量的XML文件。当然annotation的配置也有缺陷的，那就是annotation一般都是配置在代码中的，如果要修改的话，需要动源代码，丧失了灵活性，违背了OCP（增加开放，修改关闭）原则，但是在真实的项目开发中，我们只是动配置文件，而不修改源代码的情况实在是太少见了，所以现在annotation已经被广泛的运用到了编程中，各种框架都提供了基于annotation的配置。

hibernate的注解配置和Jpa中的注解使用基本上都差不多。

参考博客：

https://blog.csdn.net/ervinbao/article/details/52861000

https://www.cnblogs.com/liangxinxinbo/p/6092664.html

http://www.ilt.me/dmfx/89.html

导入jar包：

还有mysql的驱动

----------------------

简单的插入测试小案例：

实体：User

package org.model;

import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

import org.hibernate.annotations.GenericGenerator;

@Entity
// @Table(name="t_user")//表名 默认不写的话 就是类名
public class User {
    private int id;
    private String username;
    private String password;
    private String nickname;
    private Date bornDate;

    public User() {
    }

    public User(int id, String username, String password, String nickname, Date bornDate) {
        super();
        this.id = id;
        this.username = username;
        this.password = password;
        this.nickname = nickname;
        this.bornDate = bornDate;
    }

    public User(String username, String password, String nickname, Date bornDate) {
        super();
        this.username = username;
        this.password = password;
        this.nickname = nickname;
        this.bornDate = bornDate;
    }

    @Id
    @GeneratedValue()//默认native @GeneratedValue()
    //@GeneratedValue(generator = "x") //  使用uuid id的类型必须是String类型
    //@GenericGenerator(name = "x", strategy = "uuid") // 使用hibernate的uuid策略
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    @Column(length = 5, nullable = false)
    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    @Column(length = 10, nullable = false)//nullable属性：默认是true  允许空值
    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Column(length = 5, nullable = true)
    public String getNickname() {
        return nickname;
    }

    public void setNickname(String nickname) {
        this.nickname = nickname;
    }

    @Column(name = "born_date")
    public Date getBornDate() {
        return bornDate;
    }

    public void setBornDate(Date bornDate) {
        this.bornDate = bornDate;
    }

    @Override
    public String toString() {
        return "User [id=" + id + ", username=" + username + ", password=" + password + ", nickname=" + nickname
                + ", bornDate=" + bornDate + "]";
    }

}

测试类：

package org.execute;

import java.util.Date;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.junit.Test;
import org.model.User;

public class Exe {
    static Configuration config = null;
    static SessionFactory sessionFactory = null;

    // 初始化
    static {
        // 加载核心配置文件 默认加载类路径下的hibernate.cfg.xml
        config = new Configuration();
        config.configure();
        // 创建工厂
        sessionFactory = config.buildSessionFactory();
    }

    // 返回session
    public Session rtn() {
        return sessionFactory.openSession();
    }

    // 保存测试
    @Test
    public void insert() {
        Session session = rtn();
        session.getTransaction().begin();
        User u = new User("laomu", "123", "老孙", new Date());
        session.save(u);
        session.getTransaction().commit();
    }

}

我们发现在对实体进行注解配置的时候  导入的包和JPA配置时一样

在测试类中进行插入时，使用的不是JPA中的EntityManager对象，

EntityManagerFactory factory=Persistence.createEntityManagerFactory("simple");
EntityManager em = factory.createEntityManager();

而还是hibernate中的session对象。

配置文件：类路径下的hibernate.cfg.xml文件  默认会去找该文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>

    <session-factory>
        <property name="dialect">
            org.hibernate.dialect.MySQLDialect
        </property>
        <property name="hibernate.hbm2ddl.auto">update</property>
            <!--控制台打印sql语句-->
        <property name="connection.url">
            jdbc:mysql://localhost:3308/annotationhibernate
        </property>
        <property name="connection.username">root</property>
        <property name="connection.password">jay571018</property>
        <property name="connection.driver_class">
            com.mysql.jdbc.Driver
        </property>

        <property name="show_sql">true</property>
        <!--
        <mapping resource="org/model/Course.hbm.xml" />
        <mapping resource="org/model/Student.hbm.xml" />
        -->

        <mapping class="org.model.User"/>
    </session-factory>

</hibernate-configuration>

下面观察数据库：

插入的数据：

-------------------------------------------------

annotation配置many-to-one双向

先看有问题的代码：(明明配置了级联  但是却没有进行级联保存的问题)

多方：Student

package org.model;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

//多方  由该方维护外键
@Entity
@Table(name = "t_student")
public class Student {
    private int id;
    private String name;
    private String stuNo;
    // 一方的属性
    private ClassRoom room;

    @Id
    @GeneratedValue()
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    @Column(length = 5, nullable = false)
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Column(length = 10, nullable = false)
    public String getStuNo() {
        return stuNo;
    }

    public void setStuNo(String stuNo) {
        this.stuNo = stuNo;
    }

    // optional=false 外键字段不能为空 即每个学生都必须有对应的班级 默认为true
    // ManyToOne 查询student 默认使用即时加载
    @ManyToOne(cascade = { CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH })
    // 在维护端 指定外键字段名 也可以不写 默认属性_id
    @JoinColumn(name = "r_id")
    public ClassRoom getRoom() {
        return room;
    }

    public void setRoom(ClassRoom room) {
        this.room = room;
    }

    public Student() {
    }

    // 互相关联的方法
    public Student(String name, String stuNo) {
        this.name = name;
        this.stuNo = stuNo;
    }

    @Override
    public String toString() {
        return "Student [id=" + id + ", name=" + name + ", stuNo=" + stuNo + ", classRoom=" + room.toString() + "]";
    }

}

一方：ClassRoom

package org.model;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

//一方  被维护端
@Entity
@Table(name = "t_classroom")
public class ClassRoom {
    private int id;
    private String name;
    // 多方的集合属性
    private Set<Student> students = new HashSet<Student>();

    @Id
    @GeneratedValue()
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    @Column(length = 10, nullable = false)
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    // mappedBy属性：由集合中对应的实体Student中的classroom属性来维护外键 声明mappedBy的实体为被维护方
    // 抓取方式 onetoMany 默认为lazy加载
    @OneToMany(cascade = { CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH }, mappedBy = "room")
    public Set<Student> getStudents() {
        return students;
    }

    public void setStudents(Set<Student> students) {
        this.students = students;
    }

    public ClassRoom(String name) {
        this.name = name;
    }

    public ClassRoom() {}
    /*
     * public ClassRoom(int id,String name) { this.id=id; this.name = name; }
     */

    // 互相关联的方法
    public void addStudent(Student student) {
        student.setRoom(this);
        this.students.add(student);
    }

    @Override
    public String toString() {
        return "ClassRoom [id=" + id + ", name=" + name + "]";
    }

}

测试类：

    //一对多插入测试
    @Test
    public void oneToManyInsert() {
        Session session=rtn();
        session.getTransaction().begin();
        //创建对象
        Student s1=new Student("乔克","A01010");
        Student s2=new Student("小明","A01012");
        ClassRoom classRoom=new ClassRoom("就业班");
        //进行互相关联
        classRoom.addStudent(s1);
        classRoom.addStudent(s2);//在addStudent（）中进行了互相关联   这里直接调用这个方法即完成了互相关联
        //进行持久化操作
        session.save(classRoom);
        session.getTransaction().commit();
    }

然后查看数据库：

可以看到  只对classRoom表进行了数据的插入   可以我们在实体中明明配置了级联保存的操作啊   同时也进行了互相的关联  为啥会出现这种情况呢？

还记得学习JPA时级联操作触发的时机吗？----》如果使用javax.persistence.*里面的注解，只有调用相应的方法才生效，如PERSIST，只有调用persist方法才生效

所以这里当然不能实现级联了

https://blog.csdn.net/l1028386804/article/details/17686229

https://blog.csdn.net/z69183787/article/details/22327725

第一种测试：

根据网上说的情况  我了试试  如果把ClassRoom中的级联属性配置为以下的情况：

CascadeType.PESIST,CascadeType.REMOVE,CascadeType.MERGE,CascadeType.REFRESH

也不能进行级联保存，但是，如果配置为CascadeType.All则可以级联保存成功，说明

JPA中的CascadeType.ALL并不等于{CascadeType.PESIST,CascadeType.REMOVE,CascadeType.MERGE,CascadeType.REFRESH}

第二种测试：

然后我把级联属性设置成了上面说的那种方式save_update   注意  导入的是hibernate.annotation中的包  而不再是jpa中的级联包了

roomClass中的级联方式修改为：

测试结果：

级联保存成功，所以这里需要明白，hibernate注解开发 设置级联时不能使用jpa规范中的级联方式，而只能是使用自己提供的级联方式，如下：

---------------------------------------

上面进行了插入测试，下面我们进行查询测试：

可见只查询了一次数据库，在查询student对象(多方)  立即查询一方数据

因为我们在student中是这样配置的

抓取方式  在ManyToOne情况下  默认直接加载了一方属性  如果改为下面的配置方式：

执行查询  观察打印的sql

可以看到  是发送了两次sql查询  同样  在执行查询一方属性时  不指定查询方式时   默认是懒加载多方属性的  这里就不再执行了

需要注意的一点是：在查询某个实体的时候  需要在该实体中配置一个无参数的构造方法    比如  我把student实体中的无参构造删除掉  然后执行查询

所以  因为框架中好多地方都会用到无参构造  在我们创建有参构造的时候  记得把无参构造也写出来。

---------------------------------------------------------------

annotation配置many-to-one单向

student

package org.model.om.danxiang;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

@Entity
@Table(name = "danxiang_student")
public class Student {
    private int id;
    private String name;
    private String stuNo;
    // 一方的属性
    private ClassRoom room;

    @Id
    @GeneratedValue()
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    @Column(length = 5, nullable = false)
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Column(length = 10, nullable = false)
    public String getStuNo() {
        return stuNo;
    }

    public void setStuNo(String stuNo) {
        this.stuNo = stuNo;
    }

    // optional=false 外键字段不能为空 即每个学生都必须有对应的班级 默认为true
    // ManyToOne 查询student 默认使用即时加载
    //使用hibernate自己的级联方式
    @ManyToOne()
    //@Cascade({CascadeType.PERSIST,CascadeType.MERGE,CascadeType.REFRESH})
    // 在维护端 指定外键字段名 也可以不写 默认属性_id
    @JoinColumn(name = "cid")
    public ClassRoom getRoom() {
        return room;
    }

    public void setRoom(ClassRoom classRoom) {
        this.room = classRoom;
    }

    public Student() {
    }

    // 互相关联的方法
    public Student(String name, String stuNo) {
        this.name = name;
        this.stuNo = stuNo;
    }

    @Override
    public String toString() {
        return "Student [id=" + id + ", name=" + name + ", stuNo=" + stuNo + ", classRoom=" + room.toString() + "]";
    }

}

classRoom

package org.model.om.danxiang;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

//一方  被维护端
@Entity
@Table(name = "danxiang_classroom")
public class ClassRoom {
    private int id;
    private String name;
    /*
    // 多方的集合属性
    private Set<Student> students = new HashSet<Student>();*/

    @Id
    @GeneratedValue()
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    @Column(length = 10, nullable = false)
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
    /*
    // mappedBy属性：由集合中对应的实体Student中的classroom属性来维护外键 声明mappedBy的实体为被维护方
    // 抓取方式 onetoMany 默认为lazy加载
    //使用hibernate自己的级联方式
    @OneToMany(mappedBy = "room")
    @Cascade({CascadeType.PERSIST,CascadeType.MERGE,CascadeType.REFRESH})
    public Set<Student> getStudents() {
        return students;
    }

    public void setStudents(Set<Student> students) {
        this.students = students;
    }*/

    public ClassRoom(String name) {
        this.name = name;
    }

    public ClassRoom() {}
    /*
     * public ClassRoom(int id,String name) { this.id=id; this.name = name; }
     */

    /*
    // 互相关联的方法
    public void addStudent(Student student) {
        student.setRoom(this);
        this.students.add(student);
    }*/

    @Override
    public String toString() {
        return "ClassRoom [id=" + id + ", name=" + name + "]";
    }

}

测试：

    //单向  一方classroom中不创建集合   只在多方student中创建一方对象 ---》 测试成功
    //所以  单向方式操作时  只能是：在多方对象中创建一方对象属性   在一方中省略创建多方的集合属性    反之则不行  比如测试2
    @Test
    public void oneToManyInsertDanXiang() {
        Session session=rtn();
        session.getTransaction().begin();
        //创建对象
        org.model.om.danxiang.Student s1=new org.model.om.danxiang.Student("乔克","A01010");
        org.model.om.danxiang.Student s2=new org.model.om.danxiang.Student("乔克2","A01012");

        org.model.om.danxiang.ClassRoom classRoom=new org.model.om.danxiang.ClassRoom("就业班");
        //进行互相关联
        s1.setRoom(classRoom);
        s2.setRoom(classRoom);
        //保存
        session.save(classRoom);//保存的顺序无关
        session.save(s1);
        session.save(s2);

        //classRoom.addStudent(s1);
        //classRoom.addStudent(s2);//在addStudent（）中进行了互相关联   这里直接调用这个方法即完成了互相关联
        //进行持久化操作
        session.save(classRoom);
        session.getTransaction().commit();
    }

查询测试：

    //单向查询
    @Test
    public void oneToManyInsertDanXiangQuery() {
        Session session=rtn();
        //查询多方   观察是否同时查询一方数据
        org.model.om.danxiang.Student student = session.get(org.model.om.danxiang.Student.class,67);
        System.out.println(student);
    }

单向关系，查询多方的时候，可以顺带查询一方的数据   但是不能通过查询一方同时获得多方的数据   但是双向关系就可以  查询ClassRoom时  可以选择即使加载或者懒加载多方属性   然后通过ClassRoom中的students属性就可以得到多方集合数据

-----------------------------------------------

openSession和getCurrentSession的区别：

使用getCurrentSession时  出现下面错误  是因为没有开启事务

开启事务  就可以解决该问题

---------------------------------------------------

 annotation配置many-to-one双向

Person

package org.model;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;
import javax.persistence.Table;
import org.hibernate.annotations.Cascade;
import org.hibernate.annotations.CascadeType;

//一对一双向实体  person作为维护方
@Entity
@Table(name = "t_person")
public class Person {
    private int id;// 主键
    private String name;// 姓名
    private IDCard idCard;

    @Id
    @GeneratedValue
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    // 这里暂时不配置 数据库默认字段为name 可以为空 长度255
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @OneToOne
    @JoinColumn(name = "cardid")
    @Cascade(value = { CascadeType.ALL })
    public IDCard getIdCard() {
        return idCard;
    }

    public void setIdCard(IDCard idCard) {
        this.idCard = idCard;
    }

    @Override
    public String toString() {
        return "Person [id=" + id + ", name=" + name + ", idCard=" + idCard + "]";
    }

}

IDCard

package org.model;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.Table;
import org.hibernate.annotations.Cascade;
import org.hibernate.annotations.CascadeType;

//一对一双向实体
@Entity
@Table(name = "t_card")
public class IDCard {
    private int id;// 主键
    private String no;// 编号
    private Person person;

    @Id
    @GeneratedValue
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getNo() {
        return no;
    }

    public void setNo(String no) {
        this.no = no;
    }

    @OneToOne(mappedBy = "idCard")
    @Cascade(value = { CascadeType.ALL })
    public Person getPerson() {
        return person;
    }

    public void setPerson(Person person) {
        this.person = person;
    }

    @Override
    public String toString() {
        return "IDCard [id=" + id + ", no=" + no + ", person=" + person + "]";
    }

}

测试

//一对一双向关联
    @Test
    public void oneToOne() {
        Session session=rtn();
        session.getTransaction().begin();
        //创建person对象
        Person p=new Person();
        p.setName("张三");
        //创建IDCard对象
        IDCard idCard=new IDCard();
        idCard.setNo("xx1");
        //进行相互关联
        /**
         * 如果没有配置级联保存的话  那么需要相互关联  并且还要分别保存
        p.setIdCard(idCard);
        idCard.setPerson(p);
        session.save(idCard);
        session.save(p);
        */
        //配置级联之后
        p.setIdCard(idCard);
        session.save(p);
        session.getTransaction().commit();
        session.close();
    }

数据库:

-------------------------------------

annotation配置many-to-many

user

package org.model.mm.shuangxiang;

import java.util.Date;
import java.util.Set;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToMany;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import org.hibernate.annotations.Cascade;
import org.hibernate.annotations.CascadeType;
@Entity
@Table(name="mm_user")
//规定该实体为外键维护方
public class User {
    private int id;
    private String username;
    private String password;
    private String nickname;
    private Date bornDate;
    private Set<Role> roles;
    @Id
    @GeneratedValue
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    @Column(length=10,nullable=false)
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    @Column(length=10,nullable=false)
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    @Column(length=10,nullable=false)
    public String getNickname() {
        return nickname;
    }
    public void setNickname(String nickname) {
        this.nickname = nickname;
    }
    @Temporal(TemporalType.TIMESTAMP)//日期 时间 yyyy-dd-mm HH:MM:SS
    public Date getBornDate() {
        return bornDate;
    }
    public void setBornDate(Date bornDate) {
        this.bornDate = bornDate;
    }
    //以m打头   默认加载方式为lazy
    @ManyToMany()
    @Cascade(value= {CascadeType.ALL})
    /**
    @JoinTable(
    name="u_r",//中间表名称
    joinColumns=@JoinColumn(name="uid"),//本实体在中间表中创建的字段名
    inverseJoinColumns= @JoinColumn(name="rid"))//关联实体在中间表中创建的字段名
    //以上内容可以省略不写  有默认值
    */
    public Set<Role> getRoles() {
        return roles;
    }
    public void setRoles(Set<Role> roles) {
        this.roles = roles;
    }
    public User(String username, String password, String nickname, Date bornDate) {
        super();
        this.username = username;
        this.password = password;
        this.nickname = nickname;
        this.bornDate = bornDate;
    }
    public User() {}

}

role

package org.model.mm.shuangxiang;

import java.util.Set;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToMany;
import javax.persistence.Table;
import org.hibernate.annotations.Cascade;
import org.hibernate.annotations.CascadeType;

@Entity
@Table(name = "mm_role")
public class Role {
    private int id;
    private String name;
    private Set<User> users;
    @Id
    @GeneratedValue
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }
    @Column(length=10,nullable=false)
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
    @ManyToMany(mappedBy="roles")
    @Cascade(value= {CascadeType.ALL})
    public Set<User> getUsers() {
        return users;
    }

    public void setUsers(Set<User> users) {
        this.users = users;
    }

    @Override
    public String toString() {
        return "Role [id=" + id + ", name=" + name + ", users=" + users + "]";
    }

    public Role(String name) {
        super();
        this.name = name;
    }
    public Role() {}

}

测试：

//多对多不拆分
    @Test
    public void manyToMany() {
        Session session=rtn();
        session.getTransaction().begin();
        //创建user对象
        org.model.mm.shuangxiang.User user1=new org.model.mm.shuangxiang.User("zhang","123","小张",new Date());
        //org.model.mm.shuangxiang.User user2=new org.model.mm.shuangxiang.User("wang","123","小王",new Date());
        //org.model.mm.shuangxiang.User user3=new org.model.mm.shuangxiang.User("sun","123","小孙",new Date());

        //创建role对象
        Role role1=new Role("总监");
        Role role2=new Role("保安");
        Role role3=new Role("菜鸟");
        //创建集合
        Set<Role> roles=new HashSet<Role>();
        roles.add(role1);
        roles.add(role2);
        roles.add(role3);
        //进行关联
        user1.setRoles(roles);
        //保存user对象
        session.save(user1);
        session.getTransaction().commit();
        session.close();
    }

数据库：

-----------------------------------------

 annotation配置many-to-many变种  拆分为两个一对多

Student

package org.model.mm.shuangxiang2;

import java.util.Set;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import org.hibernate.annotations.Cascade;
import org.hibernate.annotations.CascadeType;

@Entity
@Table(name = "mm_student")
public class Student {
    private int id;
    private String name;
    private String stuNo;
    private Set<StudentCourse> tcs;

    @Id
    @GeneratedValue
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    @Column(length = 10, nullable = false)
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Column(length = 10, nullable = false)
    public String getStuNo() {
        return stuNo;
    }

    public void setStuNo(String stuNo) {
        this.stuNo = stuNo;
    }

    // 与中间表相比 是一方 被维护端
    @OneToMany(mappedBy = "student")
    @Cascade(value = { CascadeType.ALL })
    public Set<StudentCourse> getTcs() {
        return tcs;
    }

    public void setTcs(Set<StudentCourse> tcs) {
        this.tcs = tcs;
    }

    public Student() {
    }

    public Student(String name, String stuNo) {
        this.name = name;
        this.stuNo = stuNo;
    }
}

Course

package org.model.mm.shuangxiang2;

import java.util.Set;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import org.hibernate.annotations.Cascade;
import org.hibernate.annotations.CascadeType;

@Entity
@Table(name = "mm_course")
public class Course {
    private int id;
    private String name;
    private Set<StudentCourse> tcs;

    @Id
    @GeneratedValue
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    @Column(length = 10, nullable = false)
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    // 是一方 被维护端
    @OneToMany(mappedBy = "course")
    @Cascade(value = { CascadeType.ALL })
    public Set<StudentCourse> getTcs() {
        return tcs;
    }

    public void setTcs(Set<StudentCourse> tcs) {
        this.tcs = tcs;
    }

    public Course() {
    }

    public Course(String name) {
        this.name = name;
    }

}

中间实体  StudentCourse

package org.model.mm.shuangxiang2;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
import org.hibernate.annotations.Cascade;
import org.hibernate.annotations.CascadeType;

@Entity
@Table(name = "mm_SC") // 指定中间表名称
public class StudentCourse {
    private int id;
    private double score;
    private Student student;
    private Course course;

    @Id
    @GeneratedValue
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    @Column(length = 5, nullable = false)
    public double getScore() {
        return score;
    }

    public void setScore(double score) {
        this.score = score;
    }

    // 多方维护外键 指定中间表外键名称为student_ID
    @ManyToOne()
    @Cascade(value = { CascadeType.ALL })
    @JoinColumn(name = "student_ID")
    public Student getStudent() {
        return student;
    }

    public void setStudent(Student student) {
        this.student = student;
    }

    // 多方维护外键 指定中间表外键名称为course_ID
    @ManyToOne()
    @Cascade(value = { CascadeType.ALL })
    @JoinColumn(name = "course_ID") // 多方作为维护端
    public Course getCourse() {
        return course;
    }

    public void setCourse(Course course) {
        this.course = course;
    }

    public StudentCourse(double score, Student student, Course course) {
        super();
        this.score = score;
        this.student = student;
        this.course = course;
    }

    public StudentCourse() {
    }

}

配置文件中引入：

测试：

//多对多  拆分为两个一对多
    @Test
    public void manyToMany2() {
        Session session=rtn();
        session.getTransaction().begin();
        //创建2个student对象
        org.model.mm.shuangxiang2.Student student1=new org.model.mm.shuangxiang2.Student("zhang","141164000");
        org.model.mm.shuangxiang2.Student student2=new org.model.mm.shuangxiang2.Student("wang","141164888");
        //创建2个course对象
        Course course1=new Course("java");
        Course course2=new Course("php");
        //创建studentCourse对象  把创建的student course加入进去
        //学生1的两门课成绩
        StudentCourse sc1=new StudentCourse(88.5,student1,course1);
        StudentCourse sc2=new StudentCourse(99.5,student1,course2);
        //学生2的两门课成绩
        StudentCourse sc3=new StudentCourse(66.5,student2,course1);
        StudentCourse sc4=new StudentCourse(49.5,student2,course2);
        //保存维护端对象  studentcourse
        session.save(sc1);
        session.save(sc2);
        session.save(sc3);
        session.save(sc4);
        session.getTransaction().commit();
        session.close();
    }

数据库：

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