hibernate多对多详解

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC ???????"-//Hibernate/Hibernate Mapping DTD 3.0//EN" ???????"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><hibernate-mapping package="com.hibernate.b_manytomany"> ???????<class name="Student" table="t_student"> ???????<id name="id" ?> ????????<generator class="native"/> ????</id> ???????????<property name="studentName"/> ???????<property name="studentNumber" ></property> ???????<set name="teachers" table="student_teacher"> <!-- 关联属性teacher，创建中间表student_teacher --> ???????????<key column="student_id"></key><!-- 本方外键 --> ???????????<!-- many-to-many多对多，关联类Teacher，外键列teacher_id --> ???????????<many-to-many class="Teacher" column="teacher_id"></many-to-many> ???????</set> ???</class> ???</hibernate-mapping>

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC ???????"-//Hibernate/Hibernate Mapping DTD 3.0//EN" ???????"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><hibernate-mapping package="com.hibernate.b_manytomany"> ???????<class name="Teacher" table="t_teacher"> ???????<id name="id" ?> ????????<generator class="native"/> ????</id> ???????????<property name="teacherName"/> ???????<!-- ????????????set集合指定name为类元素student 中间表student_teacher ???????????key的column指定自己的外键为teacher_id列 ???????????many-to-many 关联类Student 以及对方的外键student_id ????????--> ???????<set name="students" table="student_teacher"> ???????????<key column="teacher_id"></key> ???????????<many-to-many class="Student" column="student_id"></many-to-many> ???????</set> ???</class> ???</hibernate-mapping>

public class Student { ???int id; ???String studentName; ???String studentNumber; ???Set<Teacher> teachers=new HashSet<Teacher>(); ???public int getId() { ???????return id; ???} ???public void setId(int id) { ???????this.id = id; ???} ???public String getStudentName() { ???????return studentName; ???} ???public void setStudentName(String studentName) { ???????this.studentName = studentName; ???} ???public String getStudentNumber() { ???????return studentNumber; ???} ???public void setStudentNumber(String studentNumber) { ???????this.studentNumber = studentNumber; ???} ???public Set<Teacher> getTeachers() { ???????return teachers; ???} ???public void setTeachers(Set<Teacher> teachers) { ???????this.teachers = teachers; ???} ???@Override ???public String toString() { ???????return "Student [id=" + id + ", studentName=" + studentName ???????????????+ ", studentNumber=" + studentNumber + "]"; ???}}

public class Teacher { ???int id; ???String teacherName; ???Set<Student> students=new HashSet<Student>(); ???public int getId() { ???????return id; ???} ???public void setId(int id) { ???????this.id = id; ???} ???public String getTeacherName() { ???????return teacherName; ???} ???public void setTeacherName(String teacherName) { ???????this.teacherName = teacherName; ???} ???public Set<Student> getStudents() { ???????return students; ???} ???public void setStudents(Set<Student> students) { ???????this.students = students; ???} ???@Override ???public String toString() { ???????return "Teacher [id=" + id + ", teacherName=" + teacherName + "]"; ???}}

public class App { ???static SessionFactory sessionFactory=null; ???static{ ???????sessionFactory =new Configuration().configure().addClass(Student.class).addClass(Teacher.class).buildSessionFactory(); ???} ???@Test ???public void addApp(){ ???????Session sess = sessionFactory.openSession(); ???????Transaction ts = null; ???????ts = sess.beginTransaction(); ???????// ???????Student student1=new Student(); ???????student1.setStudentName("studentName1"); ???????student1.setStudentNumber("000001"); ????????Student student2=new Student(); ???????student2.setStudentName("studentName2"); ???????student2.setStudentNumber("000002"); ????????Student student3=new Student(); ???????student3.setStudentName("studentName3"); ???????student3.setStudentNumber("000003"); ????????Student student4=new Student(); ???????student4.setStudentName("studentName4"); ???????student4.setStudentNumber("000004"); ????????// ???????Teacher teacher1=new Teacher(); ???????teacher1.setTeacherName("wang"); ???????Teacher teacher2=new Teacher(); ???????teacher2.setTeacherName("li"); ???????// ???????teacher1.getStudents().add(student1); ???????teacher1.getStudents().add(student2); ???????teacher1.getStudents().add(student3); ???????teacher1.getStudents().add(student4); ???????teacher2.getStudents().add(student1); ???????teacher2.getStudents().add(student3); ???????teacher2.getStudents().add(student4); ???????// ???????sess.save(teacher1); ???????sess.save(teacher2); ???????sess.save(student1); ???????sess.save(student2); ???????sess.save(student3); ???????sess.save(student4); ???????ts.commit(); ???????// TODO: handle exception ???????sess.close(); ???}