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：