hibernate 之 复合主键映射

1.在很多应用中经常会有复合主键出现的情况。比如说 成绩表，需要学生编号和课程编号组成一个复合主键。

2. 类的结构： Result.java

/**
 * 复合主键 必须实现Serializable接口
 */
public class Result implements Serializable{
    private int stuId;
    private int subId;
    private double score;
    private Date examDate;
    public Result() {
    }
    public Result(int stuId, int subId, double score, Date examDate) {
        super();
        this.stuId = stuId;
        this.subId = subId;
        this.score = score;
        this.examDate = examDate;
    }

    public int getStuId() {
        return stuId;
    }
    public void setStuId(int stuId) {
        this.stuId = stuId;
    }
    public int getSubId() {
        return subId;
    }
    public void setSubId(int subId) {
        this.subId = subId;
    }
    public double getScore() {
        return score;
    }
    public void setScore(double score) {
        this.score = score;
    }
    public Date getExamDate() {
        return examDate;
    }
    public void setExamDate(Date examDate) {
        this.examDate = examDate;
    }
    
}

3. 映射文件：

<hibernate-mapping>
    <class name="cn.wh.vo.Result" table="t_result">
        <composite-id>
            <key-property name="stuId"/>
            <key-property name="subId"/>
        </composite-id>
        <property name="score"/>
        <property name="examDate"/>
    </class>
</hibernate-mapping>

4. 测试：

public class HibernateTest {
    private Session session=null;
    @Before
    public void setUp(){
        session = HibernateUtil.getSession();
    }
    @After
    public void tearDown(){
        HibernateUtil.close();
    }
    @Test
    public void testCreateDB(){
        Configuration cfg = new Configuration().configure();
        SchemaExport export = new SchemaExport(cfg);
        //第一个参数  是否打印  数据库脚本
        //第二个参数 是否将脚本导入数据库执行
        export.create(true, true);
    }
    @Test
    public void testInit(){
        Transaction tx = null;
        try {
            tx = session.beginTransaction();
            SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
            Result r = new Result(1, 1, 90, format.parse("2016-09-12"));
            session.save(r);
            tx.commit();
            
        } catch (Exception e) {
            if(tx!=null)
                tx.rollback();
        }
    }
    @Test
    public void testGet(){
        Result r = new Result();
        r.setStuId(1);
        r.setSubId(1);
        r = (Result)session.get(Result.class, r);
        System.out.println(r.getScore()+"---"+r.getExamDate());
    }
    
}

5. 复合主键的第二类结构及写法：  ResultPK.java

/**
 * 建立一个主键类 由该类来实现序列化接口
 * @author siggy
 *
 */
public class ResultPk implements Serializable{
    private int stuId;
    private int subId;
    public ResultPk() {
        // TODO Auto-generated constructor stub
    }
    public ResultPk(int stuId, int subId) {
        super();
        this.stuId = stuId;
        this.subId = subId;
    }
    public int getStuId() {
        return stuId;
    }
    public void setStuId(int stuId) {
        this.stuId = stuId;
    }
    public int getSubId() {
        return subId;
    }
    public void setSubId(int subId) {
        this.subId = subId;
    }
    
}

Result.java

public class Result{
    private ResultPk pk;
    private double score;
    private Date examDate;
    public Result() {
    }
    public Result(ResultPk pk, double score, Date examDate) {
        super();
        this.pk = pk;
        this.score = score;
        this.examDate = examDate;
    }

    public ResultPk getPk() {
        return pk;
    }
    public void setPk(ResultPk pk) {
        this.pk = pk;
    }
    public double getScore() {
        return score;
    }
    public void setScore(double score) {
        this.score = score;
    }
    public Date getExamDate() {
        return examDate;
    }
    public void setExamDate(Date examDate) {
        this.examDate = examDate;
    }
}

6. 映射文件

<hibernate-mapping>
    <class name="cn..vo.Result" table="t_result">
        <composite-id name="pk" class="cn.wh.vo.ResultPk">
            <key-property name="stuId"/>
            <key-property name="subId"/>
        </composite-id>
        <property name="score"/>
        <property name="examDate"/>
    </class>
</hibernate-mapping>

7. 测试：

public class HibernateTest {
    private Session session=null;
    @Before
    public void setUp(){
        session = HibernateUtil.getSession();
    }
    @After
    public void tearDown(){
        HibernateUtil.close();
    }
    @Test
    public void testCreateDB(){
        Configuration cfg = new Configuration().configure();
        SchemaExport export = new SchemaExport(cfg);
        //第一个参数  是否打印  数据库脚本
        //第二个参数 是否将脚本导入数据库执行
        export.create(true, true);
    }
    @Test
    public void testInit(){
        Transaction tx = null;
        try {
            tx = session.beginTransaction();
            SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
            ResultPk pk = new ResultPk(1, 1);
            Result r = new Result(pk,90, format.parse("2016-09-12"));
            session.save(r);
            tx.commit();
            
        } catch (Exception e) {
            if(tx!=null)
                tx.rollback();
        }
    }
    @Test
    public void testGet(){
        ResultPk pk = new ResultPk(1, 1);
        Result r = (Result)session.get(Result.class, pk);
        System.out.println(r.getScore()+"---"+r.getExamDate());
    }
    
}