应用一对一关联实现级联添加数据
(作业:实现级联删除的功能)
在Record类中建立类型为IdCard的属性和对应的set()/get()方法,其关键代码如下:
private IdCard idCard;
public void setIdCard(IdCard idCard) {
this.idCard = idCard;
}
public IdCard getIdCard()
{ return idCard;
}
在Record.hbm.xml文件中映射从Record类到IdCard类的关联,其关键代码如下:
<one-to-one name="idCard" class="mrgf.IdCard" cascade="all"/>
cascade属性用来设定级联操纵对象的级别,它的可选 值 及使用方法如下表:
可选值 功能
none 默认值,不进行级联操作
save-update 当保存或裂新当前对象时,级联保存或更新关联对象
delete 当删除当前对象时,级联删除关联对象
all 当保存,更新或删除当前对象时,级联保存,更新或删除关联对象
在IdCard类中建立类型为Record的属性和对应的set()/get()方法,其关键代码如下:
private Record record;
public void setRecordId(int recordId) {
this.recordId = recordId;
}
public Record getRecord() {
return record;
}
}
在IdCard.hbm.xml文件中映射从IdCard类到IdCard类的关联,其关键代码如下:
<many-to-one name="record" class="mrgf.Record" unique="true" column="record_id"/>
本例采用外键关联,当unique属性值设为true时,表示一对一关联,它的默认值 为false(一对多关联),column属性值为映射表的外键字段名.
Hibernate的add()方法负责对象的持久化,完整代码如下:
package mrgf;
import org.class="tags" href="/tags/HIBERNATE.html" title=hibernate>hibernate.cfg.Configuration;
import org.class="tags" href="/tags/HIBERNATE.html" title=hibernate>hibernate.SessionFactory;
import org.class="tags" href="/tags/HIBERNATE.html" title=hibernate>hibernate.Session;
import org.class="tags" href="/tags/HIBERNATE.html" title=hibernate>hibernate.Transaction;
import org.class="tags" href="/tags/HIBERNATE.html" title=hibernate>hibernate.Query;
import java.util.List;
import java.io.*;
public class Hibernate {
public Hibernate() {
}
// 在静态快中加载Hibernate配置信息
private static SessionFactory class="tags" href="/tags/SESSION.html" title=session>sessionFactory;
static {
try {
Configuration config = new Configuration().configure();
class="tags" href="/tags/SESSION.html" title=session>sessionFactory = config.buildSessionFactory();
} catch (Exception e) {
System.out.println("------在初始化class="tags" href="/tags/HIBERNATE.html" title=hibernate>hibernate时抛出异常，内容如下：");
e.printStackTrace();
}
}
private Session class="tags" href="/tags/SESSION.html" title=session>session = null;
private Transaction tx = null;
//添加对象
public void add(Record record, IdCard idCard) {
// 打开Session，开启事物
class="tags" href="/tags/SESSION.html" title=session>session = class="tags" href="/tags/SESSION.html" title=session>sessionFactory.openSession();
tx = class="tags" href="/tags/SESSION.html" title=session>session.beginTransaction();
// 建立关联，并持久化
record.setIdCard(idCard);
idCard.setRecord(record);
class="tags" href="/tags/SESSION.html" title=session>session.save(record); //在这里只对实例record进行持久化.运行本例,会发现两个实例均被持久化了,这是因为前面将cascade属性值 设
为了all,将其改为none,将不会关联idcard实例.
// 提交事物，关闭Session
tx.commit();
class="tags" href="/tags/SESSION.html" title=session>session.close();
}
//检索对象
public List query(String hql) {
// 打开Session，开启事物
class="tags" href="/tags/SESSION.html" title=session>session = class="tags" href="/tags/SESSION.html" title=session>sessionFactory.openSession();
tx = class="tags" href="/tags/SESSION.html" title=session>session.beginTransaction();
// 检索数据
Query query = class="tags" href="/tags/SESSION.html" title=session>session.createQuery(hql);
List result = query.list();
// 提交事物，关闭Session
tx.commit();
class="tags" href="/tags/SESSION.html" title=session>session.close();
return result;
}
//解决表单提交中文乱码
public String toChinese(String str) {
String result = null;
try {
result = new String(str.trim().getBytes("ISO8859_1"), "GB2312");
} catch (UnsupportedEncodingException ex) {
}
return result;
}
}
query.jsp 使用
String name=request.getParameter("name");
..//此处省略了部分获得参数的代码
Record r=new Record();
r.setName(name);
..//此处省略了部分获得参数的代码
IdCard id=new IdCard();
id.setType(type);
id.setNumber(number);
Hibernate h=new Hibernate();
h.add(r,id);//调用自定义的方法
检索
List result=h.query("from Record where name='"+name+"'");
<td>证件类型：<%=record.getIdCard().getType() %></td>
<td>证件号码：<%=record.getIdCard().getNumber() %></td>
这也是级联操作起的作用. 在此只是检索了Record类.
应用一对多关联实现级联操作
Merchandise类
private MerchSort merchSort;
public void setMerchSort(MerchSort merchSort) {
this.merchSort = merchSort;
}
public MerchSort getMerchSort() {
return merchSort;
}
Merchandise.hbm.xml
<many-to-one name="merchSort" column="merchSort_id" class="mrgf.MerchSort" cascade="all" lazy="false"/>
MerchSord类
private Set merchandises=new HashSet();
public Set getMerchandises() {
return merchandises;
}
public void setMerchandises(Set merchandises) {
this.merchandises = merchandises;
}
MerchSort.hbm.xml
<set name="merchandises" cascade="all" lazy="false" inverse="true">
<key column="merchSort_id"/>
<one-to-many class="mrgf.Merchandise"/>
</set>
success.jsp
Hibernate class="tags" href="/tags/HIBERNATE.html" title=hibernate>hibernate = new Hibernate();
MerchSort merchSort=new MerchSort();
merchSort.setName(ssort); //1
Merchandise merchandiseA=new Merchandise(); //对多,A和B
merchandiseA.setName(merchA);
Merchandise merchandiseB=new Merchandise();
merchandiseB.setName(merchB);
class="tags" href="/tags/HIBERNATE.html" title=hibernate>hibernate.add(merchSort,merchandiseA,merchandiseB);
级联检索数据
<%
String hql="from MerchSort";
List list=class="tags" href="/tags/HIBERNATE.html" title=hibernate>hibernate.query(hql);
Iterator itSort=list.iterator();
while(itSort.hasNext()){
MerchSort sort=(MerchSort)itSort.next();
Set set=sort.getMerchandises(); //通过关联获得Merchandise类的对象集合
Iterator itMer=set.iterator();
while(itMer.hasNext()){
Merchandise mer=(Merchandise)itMer.next();
%>
<tr align="center">
<td><%=mer.getId() %></td>
<td><%=mer.getName() %></td><!--获得商品名称-->
<td><%=mer.getMerchSort().getName() %></td><!--获得商品类别-->
<td><%=mer.getProducingArea() %></td>
<td><%=mer.getIntroduce() %></td>
</tr>
<%
}
}
%>
Hibernate类的add方法
public void add(MerchSort merchSort, Merchandise merchandiseA, Merchandise merchandiseB) {
merchSort.getMerchandises().add(merchandiseA);//建立实例之间的关联关系
merchSort.getMerchandises().add(merchandiseB);
merchandiseA.setMerchSort(merchSort);
merchandiseB.setMerchSort(merchSort);
// 打开Session，开启事物
class="tags" href="/tags/SESSION.html" title=session>session = class="tags" href="/tags/SESSION.html" title=session>sessionFactory.openSession();
tx = class="tags" href="/tags/SESSION.html" title=session>session.beginTransaction();
// 持久化对象
class="tags" href="/tags/SESSION.html" title=session>session.save(merchSort); //只对merchSort实例化,会发现3个均被持久化了.
// 提交事物，关闭Session
tx.commit();
class="tags" href="/tags/SESSION.html" title=session>session.close();
}
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在数据库中建立了表之间的关系图.
class="tags" href="/tags/HIBERNATE.html" title=hibernate>hibernate建实体Bean的时候可自动生成1对多的关系
cascade="all" 级联等级
lazy 延迟，是指检索当前对象时，是否同时检索与当前对象关系的对象。
多对1
<many-to-one name="bbssection" class="my.bean.Bbssection" cascade="all" lazy="false">
<column name="RSID" not-null="true" />
</many-to-one>
1对多
private Set bbstopics = new HashSet(0);
public Set getBbstopics() {
return this.bbstopics;
}
public void setBbstopics(Set bbstopics) {
this.bbstopics = bbstopics;
}
<set name="bbstopics" inverse="true" cascade="all" lazy="false">
<key>
<column name="TUID" not-null="true" />
</key>
<one-to-many class="my.bean.Bbstopic" />
</set>
设置
少的.get多的().add(多的其中一个);
少的.get多的().add(多的其中另一个);
-------------------------------------------------------------------------------
1对多的添加
// 添加对象
public void add(MerchSort merchSort, Merchandise
merchandiseA, Merchandise merchandiseB) {
merchSort.getMerchandises().add(merchandiseA);
merchSort.getMerchandises().add(merchandiseB);
//HashSet的add方法。来添加多个对象
merchandiseA.setMerchSort(merchSort);
merchandiseB.setMerchSort(merchSort);
// 打开Session，开启事物
class="tags" href="/tags/SESSION.html" title=session>session = class="tags" href="/tags/SESSION.html" title=session>sessionFactory.openSession();
tx = class="tags" href="/tags/SESSION.html" title=session>session.beginTransaction();
// 持久化对象
class="tags" href="/tags/SESSION.html" title=session>session.save(merchSort);
// 提交事物，关闭Session
tx.commit();
class="tags" href="/tags/SESSION.html" title=session>session.close();
}
