hibernate笔记--组合主键映射方法

小编 2026-07-13 阅读:860 评论:0

　　一个数据库表中其主键有可能不止一个属性,同样映射到实体类中,可能有两个或多个属性共同配置成为...

　　一个数据库表中其主键有可能不止一个属性,同样映射到实体类中,可能有两个或多个属性共同配置成为一个主键,假设一个实体类Score,其主键有两个属性stuId(学生编号)和subjectId(科目编号),在hibernate环境下应该这样配置:

新建一个实体类ScoreId,属性为stuId,和subjectId,该类需要实现serializable接口(最好重写equals方法和hashcode方法):

public class ScoreId implements Serializable {    private int stuId;    private int subjectId;    public int getStuId() {        return stuId;    }    public void setStuId(int stuId) {        this.stuId = stuId;    }    public int getSubjectId() {        return subjectId;    }    public void setSubjectId(int subjectId) {        this.subjectId = subjectId;    }    public ScoreId(int stuId, int subjectId) {        super();        this.stuId = stuId;        this.subjectId = subjectId;    }    }

新建实体类Score:

public class Score {    private ScoreId scoreId;    private double result;    public ScoreId getScoreId() {        return scoreId;    }    public void setScoreId(ScoreId scoreId) {        this.scoreId = scoreId;    }    public double getResult() {        return result;    }    public void setResult(double result) {        this.result = result;    }    public Score(ScoreId scoreId, double result) {        super();        this.scoreId = scoreId;        this.result = result;    }        }

其次是Score.hbm.xml配置文件:

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC     "-//Hibernate/Hibernate Mapping DTD 3.0//EN"    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping package="com.wang.pojo">    <class name="Score" >    <composite-id name="scoreId" class="ScoreId">        <key-property name="stuId"></key-property>        <key-property name="subjectId"></key-property>    </composite-id>        <property name="result"></property>    </class></hibernate-mapping>

hibernate.cfg.xml这里就省略了,现在新建一个测试类,用于生成数据库表以及向数据库中存放一条数据:

@Test    public void testCreateDB(){        Configuration cfg = new Configuration().configure();        SchemaExport se=new SchemaExport(cfg);        //第一个参数是否生成ddl脚本 第二个参数是否执行到数据库        se.create(true,true);    }    @Test    public void testSave(){        Session session = HibernateUtil.getSession();        Transaction tx = session.beginTransaction();        Score s=new Score(new ScoreId(2,5),88);        session.save(s);        tx.commit();        session.close();    }