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:

package com.bjsxt.hibernate;

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

@Entity
@Table(name="course")
public class Course {
    private Integer id;
    
    private String name;

    @Id
    @GeneratedValue
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

Student:

package com.bjsxt.hibernate;

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;
import javax.persistence.Table;

@Entity
@Table(name="student")
public class Student {
    
    private Integer id;
    
    private String name;
    
    private Set<Course> courses = new HashSet<Course>();

    @Id
    @GeneratedValue
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @ManyToMany
    @JoinTable(name="score",
            joinColumns=@JoinColumn(name="student_id"),
            inverseJoinColumns=@JoinColumn(name="course_id")
            )
    public Set<Course> getCourses() {
        return courses;
    }

    public void setCourses(Set<Course> courses) {
        this.courses = courses;
    }
}

Score:

package com.bjsxt.hibernate;

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 Integer id;
    
    private Integer score;
    
    private Student student;
    
    private Course course;

    @Id
    @GeneratedValue
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public Integer getScore() {
        return score;
    }

    public void setScore(Integer score) {
        this.score = score;
    }

    @ManyToOne
    @JoinColumn(name="student_id")//列名
    public Student getStudent() {
        return student;
    }

    public void setStudent(Student student) {
        this.student = student;
    }

    @ManyToOne
    @JoinColumn(name="course_id")//列名
    public Course getCourse() {
        return course;
    }

    public void setCourse(Course course) {
        this.course = course;
    }
}

添加记录：

    @Test
    public void testSave(){
        Student s = new Student();
        s.setName("zhangsan");
        Course c = new Course();
        c.setName("java");
        Score score = new Score();
        score.setCourse(c);
        score.setStudent(s);
        
        Session session = sf.getCurrentSession();
        session.beginTransaction();
        
        session.save(s);
        session.save(c);
        session.save(score);
        
        session.getTransaction().commit();
    }

查询：

    @Test
    public void testLoad(){
//        testSave();
        
        Session session = sf.getCurrentSession();
        session.beginTransaction();
        
        Student s = (Student) session.load(Student.class, 2);
        for(Course c : s.getCourses()){
            System.out.println(c.getName());
        }
        
        session.getTransaction().commit();
    }

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