hibernate--student_course_score

学生, 课程,分数的设计.

a)使用联合主键@EmbeddedId  

    使用Serializable接口

b)不适用联合主键

联合主键:

3张表, 

student: id, name

course: id , name

score:studentid, courseid, score. (两个id就是联合ID)

不使用联合主键的话:

student:id, name

course: id, name

score: id,name, student, course

score--> student: many to one

course-->student: many to one 

student->course: many to many

设计:

1. 实体类(表)

2. 导航 (为了编程方便)

3. 确定编程方式

Student.java:

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;

@Entity
public class Student {
	private int id;
	private String name;
	private Set<Course> courses = new HashSet<Course>();
	
	@ManyToMany
	@JoinTable(name="score",
		joinColumns=@JoinColumn(name="student_id", referencedColumnName="id"),
		inverseJoinColumns=@JoinColumn(name="course_id", referencedColumnName="id")
		)
	public Set<Course> getCourses() {
		return courses;
	}
	public void setCourses(Set<Course> 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;
	}
	
}

Course.java:

package com.bjsxt.hibernate;

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;
	}
	
}

Score.java:

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 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;
	}
	
}

　　

hibernate.cfg.xml:

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>

         
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost/hibernate</property>
        <property name="connection.username">root</property>
        <property name="connection.password">linda0213</property>
        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
       <!--
        <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
        <property name="connection.url">jdbc:oracle:thin:@localhost:1521:SXT</property>
        <property name="connection.username">scott</property>
        <property name="connection.password">tiger</property>
      	<property name="dialect">org.hibernate.dialect.OracleDialect</property>
       -->

        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">1</property>

        

        <!-- Enable Hibernate's automatic session context management -->
        <property name="current_session_context_class">thread</property>

        <!-- Disable the second-level cache  -->
        <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>

        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>
        <property name="format_sql">true</property>

        <!-- Drop and re-create the database schema on startup
        <property name="hbm2ddl.auto">update</property>
		 -->
        <!--  
        
		<mapping resource="com/bjsxt/hibernate/Group.hbm.xml"/>
		 <mapping resource="com/bjsxt/hibernate/User.hbm.xml"/>
		 -->
		
		  <mapping class="com.bjsxt.hibernate.Student"/>
		  <mapping class="com.bjsxt.hibernate.Course"/>
		  <mapping class="com.bjsxt.hibernate.Score"/>
		  
        
		
    </session-factory>

</hibernate-configuration>

test文件:

package com.bjsxt.hibernate;

import java.util.Map;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.tool.hbm2ddl.SchemaExport;
import org.junit.AfterClass;
import org.junit.BeforeClass;
import org.junit.Test;

public class HibernateTreeTest {
	private static SessionFactory sessionFactory;
	
	@BeforeClass
	public static void beforeClass() {
		//new SchemaExport(new AnnotationConfiguration().configure()).create(false, true);
		sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
	}
	@AfterClass
	public static void afterClass() {
		sessionFactory.close();
	}
	
	@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 = sessionFactory.openSession();
		session.beginTransaction();
		session.save(s);
		session.save(c);
		session.save(score);
	
		session.getTransaction().commit();
		session.close();
	}
	@Test
	public void testLoad() {
		testSave();
		Session session = sessionFactory.openSession();
		session.beginTransaction();
		
		Student s = (Student)session.load(Student.class, 1);
		for(Course c : s.getCourses()) {
			System.out.println(c.getName());
		}
		
		session.getTransaction().commit();
		session.close();
		
	}
	
	@Test
	public void testSchemaExport() {
		new SchemaExport(new AnnotationConfiguration().configure()).create(false, true);
	}
	
	
	public static void main(String[] args) {
		beforeClass();
	}
}

最后生成的score有问题, 变成了联合主键, 所以删除掉score表, 自己建一个:

use hibernate;
create table score(id int primary key auto_increment,student_id int references student(id),course_id int references course(id), score int)

然后注释掉beforeclass里的创建表语句再次执行就没问题了.