多对多关联映射

双向的多对多关联，要求关联的双方实体类都使用Set集合属性，两端都增加集合属性的setter和getter方法。

Student类

package Mapping3;import java.util.*;public class Student {private Long id;private long studentNo;private String studentName;private int sage;private String major;/*进行多对多关联，双方互添引用对方对象的属性及方法 */private Set<Course> courses = new HashSet<Course>();public Set<Course> getCourses() {return courses;}public void setCourses(Set<Course> courses) {this.courses = courses;}public Student() {// TODO Auto-generated constructor stub}public Student(long studentNo, String studentName, int sage, String major) {this.studentNo = studentNo;this.studentName = studentName;this.sage = sage;this.major = major;}public Long getId() {return id;}public void setId(Long id) {this.id = id;}public long getStudentNo() {return studentNo;}public void setStudentNo(long studentNo) {this.studentNo = studentNo;}public String getStudentName() {return studentName;}public void setStudentName(String studentName) {this.studentName = studentName;}public int getSage() {return sage;}public void setSage(int sage) {this.sage = sage;}public String getMajor() {return major;}public void setMajor(String major) {this.major = major;}}

Student.hbm.xml

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping PUBLIC     "-//Hibernate/Hibernate Mapping DTD 3.0//EN"    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">        <!-- "http://hibernate.sourceforge.net/dtd/hibernate-mapping-3.0.dtd"> --><hibernate-mapping package="Mapping3"><class name="Student" table="student" ><id name="id" column="id"><generator class="native"/></id><property name="studentNo" type="long" column="student_no"/><property name="studentName" type="string" column="student_name"/><property name="sage" type="integer" column="sage"/><property name="major" type="string" column="major"/><!-- 双向多对多关联 --><set name="courses" table="student_course" cascade="all" ><key column="student_id" /><many-to-many column="course_id" class="Course" /></set> </class></hibernate-mapping>

Course类

package Mapping3;import java.util.*;public class Course {private Long id;private String courseName;private double ccredit;private Set<Student> students = new HashSet<Student>();public Course() {// TODO Auto-generated constructor stub}public Course(String courseName, double ccredit) {super();this.courseName = courseName;this.ccredit = ccredit;}public Long getId() {return id;}public void setId(Long id) {this.id = id;}public String getCourseName() {return courseName;}public void setCourseName(String courseName) {this.courseName = courseName;}public double getCcredit() {return ccredit;}public void setCcredit(double ccredit) {this.ccredit = ccredit;}public Set<Student> getStudents() {return students;}public void setStudents(Set<Student> students) {this.students = students;}}

Course.hbm.xml

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping PUBLIC     "-//Hibernate/Hibernate Mapping DTD 3.0//EN"    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">    <hibernate-mapping package="Mapping3"><class name="Course" table="course"  ><id name="id" column="id"><generator class="identity" /></id><property name="courseName" type="string" column="course_name"/><property name="ccredit" type="double" column="ccredit"/><!-- 双向多对多关联 --> <set name="students" table="student_course" cascade="all" > <key column="course_id" /> <many-to-many column="student_id" class="Student" /> </set></class></hibernate-mapping>

测试

package Mapping3;import java.util.*;import org.hibernate.Session;import org.hibernate.Transaction;import util.HibernateUtil;public class ManyToManyBidirectionAssociation {public static void main(String[] args) {Session session = HibernateUtil.getSession();Transaction tx = session.beginTransaction();Student student1 = new Student(20140101,"王小明",18,"计算机科学"),student2 = new Student(20140102,"李大海",20,"电子商务");Course course1 = new Course("数据结构",4),course2 = new Course("操作系统",3),course3 = new Course("数据库原理",3.5);Set<Course> courses1 = new HashSet<Course>();courses1.add(course1);courses1.add(course2);student1.setCourses(courses1);//student1选2门课Set<Course> courses2 = new HashSet<Course>();courses2.add(course1);courses2.add(course2);courses2.add(course3);student2.setCourses(courses2);//student2选3门课session.save(student1);session.save(student2);tx.commit();}}

结果