Hibernate4之多对多映射关系(十二)

程序员文章站 2022-04-14 09:17:29

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Hibernate4多对多映射关系
1.多对多单向实现
2.多对多双向实现

一、多对多单向实现

1.编写hibernateUtil类

package com.newbeedaly.util;

import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;

public class HibernateUtil {

    private static final SessionFactory sessionFactory=buildSessionFactory();

    private static SessionFactory buildSessionFactory(){
        Configuration configuration=new Configuration().configure(); // 实例化配置文件
        ServiceRegistry serviceRegistry=new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build(); // 实例化服务登记
        return configuration.buildSessionFactory(serviceRegistry); // 获取Session工厂
    }

    public static SessionFactory getSessionFactory(){
        return sessionFactory;
    }
}

2.编写hibernate.cfg.xml

<?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>

        <!--数据库连接设置 -->
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost:3306/hibernate</property>
        <property name="connection.username">root</property>
        <property name="connection.password">123456</property>


        <!-- 方言 -->
        <property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>

        <!-- 控制台显示SQL -->
        <property name="show_sql">true</property>

        <!-- 自动更新表结构 -->
        <property name="hbm2ddl.auto">update</property>

        <mapping resource="com/newbeedaly/model/Student.hbm.xml"/>
        <mapping resource="com/newbeedaly/model/Course.hbm.xml"/>

        <mapping resource="com/newbeedaly/model/Student2.hbm.xml"/>
        <mapping resource="com/newbeedaly/model/Course2.hbm.xml"/>
    </session-factory>

</hibernate-configuration>

3.编写类Student和Course

package com.newbeedaly.model;

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

public class Student {

    private int id;
    private String name;
    private Set<Course> courses=new HashSet<Course>();

    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;
    }
    public Set<Course> getCourses() {
        return courses;
    }
    public void setCourses(Set<Course> courses) {
        this.courses = courses;
    }


}

package com.newbeedaly.model;

public class Course {

    private int id;
    private String name;

    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;
    }


}

4.编写配置文件Student.hbm.xml和Course.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.newbeedaly.model">

    <class name="Student" table="t_student">
        <id name="id" column="studentId">
            <generator class="native"></generator>
        </id>

        <property name="name" column="studentName"></property>

        <set name="courses" table="student_course" cascade="save-update">
            <key column="student_id"></key>
            <many-to-many class="com.newbeedaly.model.Course" column="course_id"></many-to-many>
        </set>
    </class>

</hibernate-mapping>

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.newbeedaly.model">

    <class name="Course" table="t_course">
        <id name="id" column="courseId">
            <generator class="native"></generator>
        </id>

        <property name="name" column="courseName"></property>

    </class>

</hibernate-mapping>

5.编写StudentTest类

package com.newbeedaly.service;

import java.util.Iterator;
import java.util.Set;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.newbeedaly.model.Course;
import com.newbeedaly.model.Course2;
import com.newbeedaly.model.Student;
import com.newbeedaly.model.Student2;
import com.newbeedaly.util.HibernateUtil;

public class StudentTest {

    private SessionFactory sessionFactory=HibernateUtil.getSessionFactory();
    private Session session;

    @Before
    public void setUp() throws Exception {
        session=sessionFactory.openSession(); // 生成一个session
        session.beginTransaction(); // 开启事务
    }

    @After
    public void tearDown() throws Exception {
         session.getTransaction().commit(); // 提交事务
         session.close(); // 关闭session
    }

    @Test
    public void testSave1(){
        Course course1=new Course();
        course1.setName("语文");

        Course course2=new Course();
        course2.setName("数学");

        Student student1=new Student();
        student1.setName("张三");
        student1.getCourses().add(course1);
        student1.getCourses().add(course2);

        Student student2=new Student();
        student2.setName("李四");
        student2.getCourses().add(course1);
        student2.getCourses().add(course2);

        session.save(student1);
        session.save(student2);
    }

    @Test
    public void testLoad1(){
        Student student=(Student)session.get(Student.class, 1);
        Set<Course> courses=(Set<Course>)student.getCourses();
        Iterator it=courses.iterator();
        while(it.hasNext()){
            Course c=(Course)it.next();
            System.out.println(c.getName());
        }
    }


    @Test
    public void testSave2(){
        Course2 course1=new Course2();
        course1.setName("语文");

        Course2 course2=new Course2();
        course2.setName("数学");

        Student2 student1=new Student2();
        student1.setName("张三");
        student1.getCourses().add(course1);
        student1.getCourses().add(course2);

        Student2 student2=new Student2();
        student2.setName("李四");
        student2.getCourses().add(course1);
        student2.getCourses().add(course2);

        session.save(student1);
        session.save(student2);
    }

    @Test
    public void testLoad2(){
        Course2 course=(Course2)session.get(Course2.class, 1);
        Set<Student2> students=(Set<Student2>)course.getStudents();
        Iterator it=students.iterator();
        while(it.hasNext()){
            Student2 s=(Student2)it.next();
            System.out.println(s.getName());
        }

    }


}

二、多对多双向实现

1.编写类Course2和Student2

package com.newbeedaly.model;

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

public class Course2 {

    private int id;
    private String name;
    private Set<Student2> students=new HashSet<Student2>();

    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;
    }
    public Set<Student2> getStudents() {
        return students;
    }
    public void setStudents(Set<Student2> students) {
        this.students = students;
    }




}

package com.newbeedaly.model;

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

public class Student2 {

    private int id;
    private String name;
    private Set<Course2> courses=new HashSet<Course2>();

    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;
    }
    public Set<Course2> getCourses() {
        return courses;
    }
    public void setCourses(Set<Course2> courses) {
        this.courses = courses;
    }




}

2.编写Student2.hbm.xml和Course2.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.newbeedaly.model">

    <class name="Student2" table="t_student2">
        <id name="id" column="studentId">
            <generator class="native"></generator>
        </id>

        <property name="name" column="studentName"></property>

        <set name="courses" table="student_course2" cascade="save-update">
            <key column="student_id"></key>
            <many-to-many class="com.newbeedaly.model.Course2" column="course_id"></many-to-many>
        </set>
    </class>

</hibernate-mapping>

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.newbeedaly.model">

    <class name="Course2" table="t_course2">
        <id name="id" column="courseId">
            <generator class="native"></generator>
        </id>

        <property name="name" column="courseName"></property>

        <set name="students" table="student_course2" inverse="true" >
            <key column="course_id"></key>
            <many-to-many class="com.newbeedaly.model.Student2" column="student_id"></many-to-many>
        </set>

    </class>

</hibernate-mapping>

运行测试类

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