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:

 1 package com.qcf.pox;

 2 

 3 import java.util.HashSet;

 4 import java.util.Set;

 5 

 6 import javax.persistence.Entity;

 7 import javax.persistence.GeneratedValue;

 8 import javax.persistence.GenerationType;

 9 import javax.persistence.Id;

10 import javax.persistence.ManyToMany;

11 

12 @Entity

13 public class Course {

14     @Id

15     @GeneratedValue(strategy=GenerationType.AUTO)

16     private int id;

17     private String name;

18     @ManyToMany(mappedBy="courses")

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

20     public int getId() {

21         return id;

22     }

23     public void setId(int id) {

24         this.id = id;

25     }

26     public String getName() {

27         return name;

28     }

29     public void setName(String name) {

30         this.name = name;

31     }

32     public Set<Student2> getStudent2s() {

33         return student2s;

34     }

35     public void setStudent2s(Set<Student2> student2s) {

36         this.student2s = student2s;

37     }

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

39         super();

40         this.id = id;

41         this.name = name;

42         this.student2s = student2s;

43     }

44     public Course() {

45         super();

46     }

47     

48 }

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学生表：

 

 1 package com.qcf.pox;

 2 

 3 import java.util.HashSet;

 4 import java.util.Set;

 5 

 6 import javax.persistence.CascadeType;

 7 import javax.persistence.Entity;

 8 import javax.persistence.GeneratedValue;

 9 import javax.persistence.GenerationType;

10 import javax.persistence.Id;

11 import javax.persistence.ManyToMany;

12 

13 @Entity

14 public class Student2 {

15     @Id

16     @GeneratedValue(strategy=GenerationType.AUTO)

17     private int id;

18     private String name;

19     @ManyToMany(cascade=CascadeType.ALL)

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

21     public int getId() {

22         return id;

23     }

24     public void setId(int id) {

25         this.id = id;

26     }

27     public String getName() {

28         return name;

29     }

30     public void setName(String name) {

31         this.name = name;

32     }

33     public Set<Course> getCourses() {

34         return courses;

35     }

36     public void addCourses(Course courses) {

37         this.courses.add(courses);

38     }

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

40         super();

41         this.id = id;

42         this.name = name;

43         this.courses = courses;

44     }

45     public Student2() {

46         super();

47     }

48     

49 }

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第二步：在hibernate.cfg.xml文件中引入这两个po类

 

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

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

View Code

 

 

 

第三步：编写测试代码

 

 1 package com.qcf.test;

 2 

 3 import org.hibernate.Session;

 4 import org.hibernate.SessionFactory;

 5 import org.hibernate.Transaction;

 6 import org.hibernate.cfg.AnnotationConfiguration;

 7 import org.hibernate.cfg.Configuration;

 8 

 9 import com.qcf.pox.Course;

10 import com.qcf.pox.Student2;

11 

12 public class TestManyToMany {

13     public static void main(String[] args) {

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

15         SessionFactory factory=configuration.buildSessionFactory();

16         Session session=factory.openSession();

17         Transaction transaction=session.beginTransaction();

18         

19         //创建两个课程

20         Course course=new Course();

21         course.setName("java");

22         Course course2=new Course();

23         course2.setName("C#");

24         

25         //创建两个学生

26         Student2 student=new Student2();

27         student.setName("zhangsan");

28         Student2 student2=new Student2();

29         student2.setName("lisi");

30         

31         student.addCourses(course);

32         student.addCourses(course2);

33         

34         student2.addCourses(course);

35         student2.addCourses(course2);

36         

37         session.save(student);

38         session.save(student2);

39         

40         transaction.commit();

41         session.close();

42         

43     }

44 

45 }

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执行成功后的结果：