hibernate复合主键的使用方法

在hibernate中操作存在复合主键的数据库表记录时会有一点麻烦，需要在实体类中继承Serializable，重写它的equals(Object obj)和hasCode()方法。具体实现方法如下：

 

以BrwInfo（读者借阅信息表）为例，复合主键是BookId,ReaderId，对应的hibernate映射文件如下：

<?xml version="1.0" encoding="utf-8"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><hibernate-mapping><class name="com.library.beans.BrwInfo" table="BrwInfo" schema="dbo"catalog="Library"><composite-id><key-property name="bookId" type="java.lang.String"><column name="BookId" /></key-property><key-property name="readerId" type="java.lang.String"><column name="ReaderId" /></key-property></composite-id> //此处定义复合主键BookId,ReaderId<property name="bookName" type="java.lang.String"><column name="BookName" not-null="true" /></property><property name="readerName" type="java.lang.String"><column name="ReaderName" not-null="true" /></property><property name="brwDate" type="java.lang.String"><column name="BrwDate" not-null="true" /></property></class></hibernate-mapping>

与之对应的实体类，注意要重写equals(Object obj)和hasCode()方法。

 /** * 2010-6-13 * BrwInfo.java * author:Xiangzi * 读者借阅信息实体类 */package com.library.beans;import java.io.Serializable;import org.apache.commons.lang.builder.EqualsBuilder;import org.apache.commons.lang.builder.HashCodeBuilder;public class BrwInfo implements Serializable{private String BookId;private String ReaderId;private String BookName;private String ReaderName;private String BrwDate;public String getBookName() {return BookName;}public void setBookName(String bookName) {BookName = bookName;}public String getReaderName() {return ReaderName;}public void setReaderName(String readerName) {ReaderName = readerName;}public String getBookId() {return BookId;}public void setBookId(String bookId) {BookId = bookId;}public String getReaderId() {return ReaderId;}public void setReaderId(String readerId) {ReaderId = readerId;}public String getBrwDate() {return BrwDate;}public void setBrwDate(String brwDate) {BrwDate = brwDate;}public boolean equals(Object obj) {if (!(obj instanceof BrwInfo)) {return false;}BrwInfo brw = (BrwInfo) obj;return new EqualsBuilder().appendSuper(super.equals(obj)).append(this.BookId, brw.BookId).append(this.ReaderId, brw.ReaderId).isEquals();}public int hasCode() {return new HashCodeBuilder(-528253723, -475504089).appendSuper(super.hashCode()).append(this.BookId).append(this.ReaderId).toHashCode();}}

下面就可以在数据层实现对这个表的GRUD操作了，示例如下。

/** 删除借阅信息* @param readerId 读者id* @param bookId 图书id*/public void delete(String readerId, String bookId) {BrwInfo brwInfo=new BrwInfo();brwInfo.setBookId(bookId);brwInfo.setReaderId(readerId);this.getHibernateTemplate().delete(this.getHibernateTemplate().get(BrwInfo.class,brwInfo));}/* * 按readerId,bookId查询借阅信息* @param readerId 读者id* @param bookId 图书id* @return BrwInfo 借阅实体*/public BrwInfo queryById(String readerId, String bookId) {BrwInfo brwInfo=new BrwInfo();brwInfo.setBookId(bookId);brwInfo.setReaderId(readerId);return (BrwInfo) this.getHibernateTemplate().get(BrwInfo.class,brwInfo);}