多对多 映射 检索

package com.lan.Hib;

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

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.Transaction;

import com.lan.Hib.domain.Student;
import com.lan.Hib.domain.Teacher;

public class Many2Many {
	public static void main(String[] args) {
		add();
		query(1);
	}
	
	
	static void add(){
		Session session = null;
		Transaction tx = null;
		try {
			Set<Teacher> teachers = new LinkedHashSet<Teacher>();
			Teacher teacher1 = new Teacher();
			Teacher teacher2 = new Teacher();
			teacher1.setName("teacher1 name");
			teacher2.setName("teacher2 name");
			teachers.add(teacher1);
			teachers.add(teacher2);
			
			Set<Student> students = new LinkedHashSet<Student>();
			Student student1 = new Student();
			Student student2 = new Student();
			student1.setName("student1 name");
			student2.setName("student2 name");
			students.add(student1);
			students.add(student2);
			
			teacher1.setStudents(students);
			teacher2.setStudents(students);
			//student1.setTeachers(teachers);
			//student2.setTeachers(teachers);
			
			session = HibernateUtil.getSession();
			tx = session.beginTransaction();
			
			session.save(teacher1);
			session.save(teacher2);
			session.save(student1);
			session.save(student2);
			
			tx.commit();
		} catch (HibernateException e) {
			if (tx != null) {
				tx.rollback();
			}
			throw e;
		} finally{
			if(session != null){
				session.close();
			}
		}
	}
	
	
	static void query(int id){
		Session session = null;
		Transaction tx = null;
		try {
			session = HibernateUtil.getSession();
			tx = session.beginTransaction();
			
			Teacher teacher = (Teacher) session.get(Teacher.class, id);
			System.out.println("students size:"+ teacher.getStudents().size());
			Student[] students =  teacher.getStudents().toArray(new Student[0]);
		
			for(int i = 0;i < students.length;i++){
				System.out.println(students[i].getName());
			}
			tx.commit();
		} finally{
			if(session != null){
				session.close();
			}
		}
	}
}

package com.lan.Hib.domain;

import java.util.Set;

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;
	}
	
}

<?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.lan.Hib.domain">

	<class name="Teacher" >
		
		<id name="id" column="id"> <!--属性   字段-->
			<generator class="native"/>
		</id>
		
		<property name="name"/>
		<set name="students" table="teacher_student">
			<key column="teacher_id"></key>
			<many-to-many class="Student" column="student_id"/>
		</set>
	</class>
</hibernate-mapping>

package com.lan.Hib.domain;

import java.util.Set;

public class Student {
	private int id;
	private String name;
	private Set<Teacher> teachers;
	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;
	}
}

<?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.lan.Hib.domain">

	<class name="Student">
		
		<id name="id" column="id"> <!--属性   字段-->
			<generator class="native"/>
		</id>
		
		<property name="name"/>
		<set name="teachers" table="teacher_student">
			<key column="student_id"></key>
			<many-to-many class="Teacher" column="teacher_id"/>
		</set>
	</class>
</hibernate-mapping>