Hibernate进阶之多对多双向关联

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package cn.itcast.d_many22many;import java.util.Date;import java.util.HashSet;import java.util.Set;import javassist.expr.NewArray;/** * 项目 *  * @author Jie.Yuan *  */public class Student {private int id;private String name;private Set<Teacher> teachers=new HashSet<Teacher>();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<Teacher> getTeachers() {return teachers;}public void setTeachers(Set<Teacher> teachers) {this.teachers = teachers;}@Overridepublic String toString() {return "Student [id=" + id + ", name=" + name + ", teachers="+ teachers + "]";}}

package cn.itcast.d_many22many;import java.util.HashSet;import java.util.Set;import javassist.expr.NewArray;/** * 开发人员 *  * @author Jie.Yuan *  */public class Teacher {private int id;private String name;private Set<Student> students;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<Student> getStudents() {return students;}public void setStudents(Set<Student> students) {this.students = students;}@Overridepublic String toString() {return "Teacher [id=" + id + ", name=" + name + ", students="+ students + "]";}}

student.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="cn.itcast.d_many22many"><class name="Student" table="student"><id name="id"><generator class="native"></generator></id><property name="name" column="name"/><set name="teachers" table="teacher_student">           <key column="student_id"></key><!-- 查找这个学生被那个老师教 -->           <many-to-many class="Teacher" column="teacher_id"></many-to-many>       </set></class></hibernate-mapping>

teacher.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="cn.itcast.d_many22many"><class name="Teacher" table="teacher"><id name="id" column="id"><generator class="native"></generator></id><property name="name" column="name" /><set name="students" table="teacher_student">  <!--查老师的id的  和中间表联系-->           <key column="teacher_id"/>           <!-- 查学生的id和中间表的关系 -->           <many-to-many class="Student" column="student_id"></many-to-many></set></class></hibernate-mapping>

测试类

package cn.itcast.d_many22many;import java.util.HashSet;import java.util.Iterator;import java.util.Set;import org.hibernate.classic.Session;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;import org.junit.Test;import cn.itcast.d_many22many.Student;import cn.itcast.d_many22many.Teacher;public class App_many22many {//双向多对多private static SessionFactory sf;static {sf = new Configuration().configure().addClass(Student.class)   .addClass(Teacher.class)   // 测试时候使用.buildSessionFactory();}@Testpublic void add(){Session session = sf.openSession();session.beginTransaction(); Teacher t1 = new Teacher();         t1.setName("王老师");         Teacher t2 = new Teacher();         t2.setName("李老师");         Student s1 = new Student();         s1.setName("王同学");         Student s2 = new Student();         s2.setName("李同学");         Set<Student> ss = new HashSet<Student>();         ss.add(s1);         ss.add(s2);                 t1.setStudents(ss);// 告诉Hibernate老师教了那两个学生         t2.setStudents(ss);                 session.save(t1);         session.save(t2);         session.save(s1);         session.save(s2);session.getTransaction().commit();session.close();}@Testpublic void query(){//双向关联体现在查找上Session session = sf.openSession();session.beginTransaction();Teacher teacher = (Teacher) session.get(Teacher.class, 2);System.out.println("教室的姓名:" + teacher.getName());System.out.println("教室的学生列表：");Iterator<Student> iterator = teacher.getStudents().iterator();while (iterator.hasNext()) {Student student = iterator.next();System.out.println(student.getName() + "   ");}System.out.println("===========逆向==============");Student student = (Student) session.get(Student.class, 1);System.out.println("学生的姓名:" + student.getName());System.out.println("学生被教的老师:");Iterator<Teacher> iterator2 = student.getTeachers().iterator();while (iterator2.hasNext()) {Teacher teacher2 = iterator2.next();System.out.println(teacher2.getName() + "  ");}System.out.println();session.getTransaction().commit();session.close();}}

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