Hibernate Student_Course_Score设计

示例：

设计代码，实现在数据库中建student表、course表、和score表，展现三者关系

student表：id、name

course表：id、name

score表：id、score、student_id、course_id

三张表的关联关系如下：

设计思路：

1.首先创建Student实体类和Course实体类

会自动创建中间表，通过@JoinTable注解，设置中间表名为“score”，属性名分别为“student_id”和“course_id”

@ManyToMany@JoinTable(name="score",    joinColumns={@JoinColumn(name="student_id")},    inverseJoinColumns={@JoinColumn(name="course_id")})

2.创建实体类Score

    PRivate int id;     private int score;     private Student student;     private Course course;

根据步骤1中创建的中间表，通过@Table注解设置表名为“score”，

通过@ManyToOne注解设置属性名分别为“student_id”和“course_id”

3.Junit测试类

@Testpublic void test() {    new SchemaExport(new Configuration().configure()).create(true, true);}

具体实现代码如下：

1.Student类

@Entitypublic class Student {private int id;private String name;private Set<Course> courses = new HashSet<Course>();@Id@GeneratedValuepublic 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;}@ManyToMany@JoinTable(name="score",                                                 //中间表名joinColumns={@JoinColumn(name="student_id")},            //属性名inverseJoinColumns={@JoinColumn(name="course_id")})      //属性名public Set<Course> getCourses() {return courses;}public void setCourses(Set<Course> courses) {this.courses = courses;}}

2.Course类

@Entitypublic class Course {private int id;private String name;@Id@GeneratedValuepublic 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;}}

3.Score类

@Entity@Table(name="score")      //对应中间表名public class Score {private int id;private int score;private Student student;private Course course;@Id@GeneratedValuepublic 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")    //对应属性名public Student getStudent() {return student;}public void setStudent(Student student) {this.student = student;}@ManyToOne()@JoinColumn(name="course_id")    //对应属性名public Course getCourse() {return course;}public void setCourse(Course course) {this.course = course;}}

4.存储一条数据

@Testpublic void testsave() {session session = sf.getCurrentSession();session.beginTransaction();Student s = new Student();s.setName("lisi");Course c = new Course();c.setName("c++");Score score = new Score();score.setStudent(s);score.setCourse(c);//score.setScore(90);  //若不设置，默认为0session.save(s);session.save(c);session.save(score);session.getTransaction().commit();}

注意：

create table score (id integer not null, score integer not null, course_id integer, student_id integer not null auto_increment, primary key (student_id, course_id)) 运行程序，会发现通过程序自动建的score表是有问题的。 我们想要的是，id为主键，且自增 而结果是，student_id和course_id为联合主键，且student_id自增 这是hibernate自身的bug，所以应该手动去数据库中，修改表的结构