学生、课程、分数的设计（重要）

a) 使用联合主键@Embedded
i. 实现 Serializable 接口
b) 不使用联合主键
i. 并不存在唯一的一种映射关系

表之间的关系：

类之间的关系：

Student 和 Course 是多对多的单向关联，根据需求，一般都是学生包括课程，课程不包含学生（根据需求确定）；

Score 中组合了Student和Course类。类图如下：

Course:

 1 package com.bjsxt.hibernate;
 2 
 3 import javax.persistence.Entity;
 4 import javax.persistence.GeneratedValue;
 5 import javax.persistence.Id;
 6 import javax.persistence.Table;
 7 
 8 @Entity
 9 @Table(name="course")
10 public class Course {
11     private Integer id;
12     
13     private String name;
14 
15     @Id
16     @GeneratedValue
17     public Integer getId() {
18         return id;
19     }
20 
21     public void setId(Integer id) {
22         this.id = id;
23     }
24 
25     public String getName() {
26         return name;
27     }
28 
29     public void setName(String name) {
30         this.name = name;
31     }
32 }

Student:

 1 package com.bjsxt.hibernate;
 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.Id;
 9 import javax.persistence.JoinColumn;
10 import javax.persistence.JoinTable;
11 import javax.persistence.ManyToMany;
12 import javax.persistence.Table;
13 
14 @Entity
15 @Table(name="student")
16 public class Student {
17     
18     private Integer id;
19     
20     private String name;
21     
22     private Set<Course> courses = new HashSet<Course>();
23 
24     @Id
25     @GeneratedValue
26     public Integer getId() {
27         return id;
28     }
29 
30     public void setId(Integer id) {
31         this.id = id;
32     }
33 
34     public String getName() {
35         return name;
36     }
37 
38     public void setName(String name) {
39         this.name = name;
40     }
41 
42     @ManyToMany
43     @JoinTable(name="score",
44             joinColumns=@JoinColumn(name="student_id"),
45             inverseJoinColumns=@JoinColumn(name="course_id")
46             )
47     public Set<Course> getCourses() {
48         return courses;
49     }
50 
51     public void setCourses(Set<Course> courses) {
52         this.courses = courses;
53     }
54 }

Score:

 1 package com.bjsxt.hibernate;
 2 
 3 import javax.persistence.Entity;
 4 import javax.persistence.GeneratedValue;
 5 import javax.persistence.Id;
 6 import javax.persistence.JoinColumn;
 7 import javax.persistence.ManyToOne;
 8 import javax.persistence.Table;
 9 
10 @Entity
11 @Table(name="score")
12 public class Score {
13     
14     private Integer id;
15     
16     private Integer score;
17     
18     private Student student;
19     
20     private Course course;
21 
22     @Id
23     @GeneratedValue
24     public Integer getId() {
25         return id;
26     }
27 
28     public void setId(Integer id) {
29         this.id = id;
30     }
31 
32     public Integer getScore() {
33         return score;
34     }
35 
36     public void setScore(Integer score) {
37         this.score = score;
38     }
39 
40     @ManyToOne
41     @JoinColumn(name="student_id")//列名
42     public Student getStudent() {
43         return student;
44     }
45 
46     public void setStudent(Student student) {
47         this.student = student;
48     }
49 
50     @ManyToOne
51     @JoinColumn(name="course_id")//列名
52     public Course getCourse() {
53         return course;
54     }
55 
56     public void setCourse(Course course) {
57         this.course = course;
58     }
59 }

添加记录：

 1     @Test
 2     public void testSave(){
 3         Student s = new Student();
 4         s.setName("zhangsan");
 5         Course c = new Course();
 6         c.setName("java");
 7         Score score = new Score();
 8         score.setCourse(c);
 9         score.setStudent(s);
10         
11         Session session = sf.getCurrentSession();
12         session.beginTransaction();
13         
14         session.save(s);
15         session.save(c);
16         session.save(score);
17         
18         session.getTransaction().commit();
19     }

View Code

查询：

 1     @Test
 2     public void testLoad(){
 3 //        testSave();
 4         
 5         Session session = sf.getCurrentSession();
 6         session.beginTransaction();
 7         
 8         Student s = (Student) session.load(Student.class, 2);
 9         for(Course c : s.getCourses()){
10             System.out.println(c.getName());
11         }
12         
13         session.getTransaction().commit();
14     }

View Code

jar包链接: https://pan.baidu.com/s/1dF26ybf 密码: 4mrf

代码链接: https://pan.baidu.com/s/1dFmrwnZ 密码: ynmp