Many-To-Many （学生、课程、分数）

Many-To-Many （学生、课程、分数）

博客分类：  Hibernate 4.1

manytomany 

Many-To-Many （学生、课程、分数）

多对多： 
一个学生可以选多门课 
一门课可以被多个学生选修 

多对一： 
多组分数对应一个学生 
多组分数对应一门课程 

多对多要有三张表 分别为： student、course、sorce 
一、Student.java 

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

 import javax.persistence.Entity;
 import javax.persistence.GeneratedValue;
 import javax.persistence.Id;
 import javax.persistence.JoinColumn;
 import javax.persistence.JoinTable;
 import javax.persistence.ManyToMany;

 @Entity
 public class Student {
     private int id;
     private String name;
     private Set courses = new HashSet();

     @ManyToMany
          //设置第三张表score与student和course表之间的外键连接，操作其中两张表的数据时，成绩表数据也会被操作
     @JoinTable(name="score",
         joinColumns=@JoinColumn(name="student_id", referencedColumnName="id"),
         inverseJoinColumns=@JoinColumn(name="course_id", referencedColumnName="id")
         )
     public Set getCourses() {
         return courses;
     }
     public void setCourses(Set courses) {
         this.courses = courses;
     }
     @Id
     @GeneratedValue
     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;
     }

 }

二、Course.java 

 import javax.persistence.Entity;
 import javax.persistence.GeneratedValue;
 import javax.persistence.Id;

 @Entity
 public class Course {
     private int id;
     private String name;
     @Id
     @GeneratedValue
     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;
     }

 }

三、Score.java 

 import javax.persistence.Entity;
 import javax.persistence.GeneratedValue;
 import javax.persistence.Id;
 import javax.persistence.JoinColumn;
 import javax.persistence.ManyToOne;
 import javax.persistence.Table;

 @Entity
 @Table(name="score")
 public class Score {
     private int id;
     private int score;
     private Student student;
     private Course course;
     @Id
     @GeneratedValue
     public int getId() {
         return id;
     }
     public void setId(int id) {
         this.id = id;
     }
     public int getScore() {
         return score;
     }
     public void setScore(int score) {
         this.score = score;
     }
     @ManyToOne
     @JoinColumn(name="student_id")
     public Student getStudent() {
         return student;
     }
     public void setStudent(Student student) {
         this.student = student;
     }

     @ManyToOne
     @JoinColumn(name="course_id")
     public Course getCourse() {
         return course;
     }
     public void setCourse(Course course) {
         this.course = course;
     }

 }