Hibernat之关系的处理多对多

第一步：编写两个pojo，比如一个学生表一个课程表  这里使用注解。

需要

课程表:

 package com.qcf.pox;

 import java.util.HashSet;

 import java.util.Set;

 import javax.persistence.Entity;

 import javax.persistence.GeneratedValue;

 import javax.persistence.GenerationType;

 import javax.persistence.Id;

 import javax.persistence.ManyToMany;

 @Entity

 public class Course {

     @Id

     @GeneratedValue(strategy=GenerationType.AUTO)

     private int id;

     private String name;

     @ManyToMany(mappedBy="courses")

     private Set<Student2> student2s=new HashSet<Student2>();

     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<Student2> getStudent2s() {

         return student2s;

     }

     public void setStudent2s(Set<Student2> student2s) {

         this.student2s = student2s;

     }

     public Course(int id, String name, Set<Student2> student2s) {

         super();

         this.id = id;

         this.name = name;

         this.student2s = student2s;

     }

     public Course() {

         super();

     }

 }

学生表：

 package com.qcf.pox;

 import java.util.HashSet;

 import java.util.Set;

 import javax.persistence.CascadeType;

 import javax.persistence.Entity;

 import javax.persistence.GeneratedValue;

 import javax.persistence.GenerationType;

 import javax.persistence.Id;

 import javax.persistence.ManyToMany;

 @Entity

 public class Student2 {

     @Id

     @GeneratedValue(strategy=GenerationType.AUTO)

     private int id;

     private String name;

     @ManyToMany(cascade=CascadeType.ALL)

     private Set<Course> courses=new HashSet<Course>();

     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<Course> getCourses() {

         return courses;

     }

     public void addCourses(Course courses) {

         this.courses.add(courses);

     }

     public Student2(int id, String name, Set<Course> courses) {

         super();

         this.id = id;

         this.name = name;

         this.courses = courses;

     }

     public Student2() {

         super();

     }

 }

第二步：在hibernate.cfg.xml文件中引入这两个po类

         <mapping class="com.qcf.pox.Student2"/>

         <mapping class="com.qcf.pox.Course"/>

第三步：编写测试代码

 package com.qcf.test;

 import org.hibernate.Session;

 import org.hibernate.SessionFactory;

 import org.hibernate.Transaction;

 import org.hibernate.cfg.AnnotationConfiguration;

 import org.hibernate.cfg.Configuration;

 import com.qcf.pox.Course;

 import com.qcf.pox.Student2;

 public class TestManyToMany {

     public static void main(String[] args) {

         Configuration configuration=new AnnotationConfiguration().configure();

         SessionFactory factory=configuration.buildSessionFactory();

         Session session=factory.openSession();

         Transaction transaction=session.beginTransaction();

         //创建两个课程

         Course course=new Course();

         course.setName("java");

         Course course2=new Course();

         course2.setName("C#");

         //创建两个学生

         Student2 student=new Student2();

         student.setName("zhangsan");

         Student2 student2=new Student2();

         student2.setName("lisi");

         student.addCourses(course);

         student.addCourses(course2);

         student2.addCourses(course);

         student2.addCourses(course2);

         session.save(student);

         session.save(student2);

         transaction.commit();

         session.close();

     }

 }

执行成功后的结果：