Hibernate 多对多映射

package com.entity.manytomany;



import java.util.List;



import javax.persistence.Entity;

import javax.persistence.JoinColumn;

import javax.persistence.JoinTable;

import javax.persistence.ManyToMany;



import com.entity.BaseEntity;

@Entity

public class Student extends BaseEntity{

	private String name;

	@ManyToMany

	//学生是不稳定的一方 所以由学生来维护

	@JoinTable(name="student_course",

				joinColumns=@JoinColumn(name="s_id"),

				inverseJoinColumns=@JoinColumn(name="c_id"))

	//关联表的表名

	//关联当前表的主键

	//关联对方表的主键   （）内的name即关联表内的字段名   可以自己自由设计

	private List<Course> courses;

	public String getName() {

		return name;

	}

	public void setName(String name) {

		this.name = name;

	}

	public List<Course> getCourses() {

		return courses;

	}

	public void setCourses(List<Course> courses) {

		this.courses = courses;

	}

	

	

}

student.java

package com.entity.manytomany;



import java.util.List;



import javax.persistence.Entity;

import javax.persistence.ManyToMany;



import com.entity.BaseEntity;

@Entity

public class Course extends BaseEntity{

	private String name;

	@ManyToMany(mappedBy ="courses")

	//被学生类的courses对象维护

	private List<Student> students;

	public String getName() {

		return name;

	}

	public void setName(String name) {

		this.name = name;

	}

	public List<Student> getStudents() {

		return students;

	}

	public void setStudents(List<Student> students) {

		this.students = students;

	}

	

}

 Course.java

 

package com;



import java.util.ArrayList;

import java.util.List;



import org.hibernate.Session;

import org.hibernate.Transaction;

import org.junit.After;

import org.junit.Before;

import org.junit.Test;



import com.entity.manytomany.Course;

import com.entity.manytomany.Student;



public class TestManyToMany {

	private Session s;

	private Transaction tran;

@Before

public void before(){

	s=HibernateUtils.getSession();

	tran=s.beginTransaction();

	

}



public void manytomany(){

	Course c1=new Course();

	Course c2=new Course();

	Course c3=new Course();

	Student stu1=new Student();

	Student stu2=new Student();

	Student stu3=new Student();

	stu1.setName("zhangsan");

	stu2.setName("lisi");

	stu3.setName("wangwu");

	c1.setName("java");

	c2.setName("oracle");

	c3.setName("html");

	//新建对象

	List<Course> courses =new ArrayList<Course>();//建立了一个课程集合

	List<Course> courses1 =new ArrayList<Course>();

	courses1.add(c2);

	courses1.add(c3);

	courses.add(c1);

	courses.add(c2);

	courses.add(c3);

	//向集合中插入要选的课程

	stu1.setCourses(courses);

	stu2.setCourses(courses);

	stu3.setCourses(courses1);

	//建立关联   将课程集合set到学生的课程属性中   即学生选择了集合中所有的课程

	s.save(c1);

	s.save(c2);

	s.save(c3);

	s.save(stu1);

	s.save(stu2);

	s.save(stu3);

}	

@Test

public void manytomanyquery(){

	Course c=(Course)s.get(Course.class, 1);

	for(Student s:c.getStudents()){

		System.out.println(c.getName()+"-------选这门课的学生"+s.getName());

	}

	Course c1=(Course)s.get(Course.class, 2);

	for(Student s:c1.getStudents()){

		System.out.println(c1.getName()+"-------选这门课的学生"+s.getName());

	}

	Course c2=(Course)s.get(Course.class, 3);

	for(Student s:c2.getStudents()){

		System.out.println(c1.getName()+"-------选这门课的学生"+s.getName());

	}

}

@After

public void after(){

	tran.commit();

	s.close();

}

}

 testmanytomany.java