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