Hibernate---->component映射和复合主键映射

一、组件(Component)

 

组件(Component)是一个被包含的对象，在持久化的过程中，它被当作值类型，而并非一个实体的引用。 如姓名(Name)可以作为人(Person)的一个组件,在hibernate中,component是某个实体的逻辑组成部分，它与实体的根本区别是没有oid(object Id)，component可以成为是值对象（DDD）
Person.java

public class Person {    private java.util.Date birthday;    private Name name;    private String key;    public String getKey() {        return key;    }    private void setKey(String key) {        this.key=key;    }    public java.util.Date getBirthday() {        return birthday;    }    public void setBirthday(java.util.Date birthday) {        this.birthday = birthday;    }    public Name getName() {        return name;    }    public void setName(Name name) {        this.name = name;    }    ......    ......}

Name.java

public class Name {    char initial;    String first;    String last;    public String getFirst() {        return first;    }    void setFirst(String first) {        this.first = first;    }    public String getLast() {        return last;    }    void setLast(String last) {        this.last = last;    }    public char getInitial() {        return initial;    }    void setInitial(char initial) {        this.initial = initial;    }}

在持久化的过程中,姓名(Name)可以作为人(Person)的一个组件。需要注意的是:你应该为姓名的持久化属性定义getter和setter方法,但是你不需要实现任何的接口或申明标识符字段。

以下是这个例子的Hibernate映射文件:

<class name="eg.Person" table="person">    <id name="Key" column="pid" type="string">        <generator class="uuid"/>    </id>    <property name="birthday" type="date"/>    <component name="Name" class="eg.Name"> <!-- class attribute optional -->        <property name="initial"/>        <property name="first"/>        <property name="last"/>    </component></class>

人员(Person)表中将包括pid, birthday, initial, first和 last等字段。

二、复合主键映射（hibernate强烈不建议使用）

通常将复合主键相关的属性，单独放到一个类中
 * 此类必须实现序列化接口
 * 覆写hashcode和equals方法(因为主键不能重复)

FiscalYearPeriodPK.java(包含要一起作为主键的元素)

package com.ncepu.hibernate;import java.io.Serializable;public class FiscalYearPeriodPK implements Serializable {//核算年private int fiscalYear;//核算月private int fiscalPeriod;public int getFiscalYear() {return fiscalYear;}public void setFiscalYear(int fiscalYear) {this.fiscalYear = fiscalYear;}public int getFiscalPeriod() {return fiscalPeriod;}public void setFiscalPeriod(int fiscalPeriod) {this.fiscalPeriod = fiscalPeriod;}@Overridepublic int hashCode() {final int prime = 31;int result = 1;result = prime * result + fiscalPeriod;result = prime * result + fiscalYear;return result;}@Overridepublic boolean equals(Object obj) {if (this == obj)return true;if (obj == null)return false;if (getClass() != obj.getClass())return false;final FiscalYearPeriodPK other = (FiscalYearPeriodPK) obj;if (fiscalPeriod != other.fiscalPeriod)return false;if (fiscalYear != other.fiscalYear)return false;return true;}}

FiscalYearPeriod.java

package com.ncepu.hibernate;import java.util.Date;  /** * 核算期间 * @author wangy * */public class FiscalYearPeriod {private FiscalYearPeriodPK fiscalYearPeriodPK;//开始日期private Date beginDate;//结束日期private Date endDate;//状态private String periodSts;public Date getBeginDate() {return beginDate;}public void setBeginDate(Date beginDate) {this.beginDate = beginDate;}public Date getEndDate() {return endDate;}public void setEndDate(Date endDate) {this.endDate = endDate;}public String getPeriodSts() {return periodSts;}public void setPeriodSts(String periodSts) {this.periodSts = periodSts;}public FiscalYearPeriodPK getFiscalYearPeriodPK() {return fiscalYearPeriodPK;}public void setFiscalYearPeriodPK(FiscalYearPeriodPK fiscalYearPeriodPK) {this.fiscalYearPeriodPK = fiscalYearPeriodPK;}}

映射文件

<hibernate-mapping><class name="com.ncepu.hibernate.FiscalYearPeriod" table="t_fiscal_year_period"><composite-id name="fiscalYearPeriodPK"><key-property name="fiscalYear"/><key-property name="fiscalPeriod"/></composite-id><property name="beginDate"/><property name="endDate"/><property name="periodSts"/></class></hibernate-mapping>

加载

  public void testLoad1() {   Session session = null;   try {    session = HibernateUtils.getSession();    session.beginTransaction();        FiscalYearPeriodPK pk = new FiscalYearPeriodPK();    pk.setFiscalYear(2008);    pk.setFiscalPeriod(8);        //这里session.load()中的第一个参数传的是可序列化的id,这里传一个FiscalYearPeriodPK对象.    FiscalYearPeriod fiscalYearPeriod=(FiscalYearPeriod)session.load(FiscalYearPeriod.class, pk);        System.out.println(fiscalYearPeriod.getPeriodSts());        session.getTransaction().commit();   }catch(Exception e) {    e.printStackTrace();    session.getTransaction().rollback();   }finally {    HibernateUtils.closeSession(session);   }  }