java AJAX实现级联下拉框

package com.ajaxlab.ajax;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.input.SAXBuilder;
import com.ajaxlab.ajax.ProductClass;

public class ClassService ...{
private Document dom;
public ClassService()...{
try...{
SAXBuilder builder=new SAXBuilder();
this.dom=builder.build(ClassService.class.getResource("product.xml"));
}catch(Exception e)...{
e.printStackTrace();
}
}
public ProductClass[] getAllClass1()...{
Collection products=new ArrayList();
Iterator iterator=this.dom.getRootElement().getChildren().iterator();
do...{
Element element=(Element)iterator.next();
ProductClass product=new ProductClass(element.getAttributeValue("id"),
element.getAttributeValue("className"));
products.add(product);
}while(iterator.hasNext());
return (ProductClass[])products.toArray(new ProductClass[0]);

}

public ProductClass[] getAllClass2ById(String class1Id)...{
Collection products=new ArrayList();
Element classElement=null;
Iterator iterator=this.dom.getRootElement().getChildren().iterator();
do...{
Element element=(Element)iterator.next();
if(class1Id.equalsIgnoreCase(element.getAttributeValue("id")))...{
classElement=element;
break;
}
}while(iterator.hasNext());

if(classElement!=null)...{
Iterator iter=classElement.getChildren().iterator();
do...{
Element element=(Element)iter.next();
ProductClass product=new ProductClass(element.getAttributeValue("id"),
element.getAttributeValue("className"));
products.add(product);
}while(iter.hasNext());
return (ProductClass[])products.toArray(new ProductClass[0]);
}
else...{
return null;
}
}


public ProductClass[] getAllClass3ById(String class1Id,String class2Id) ...{
Collection products = new ArrayList();
Element class1Element = null;
Element class2Element = null;

Iterator iterator = this.dom.getRootElement().getChildren().iterator();
do ...{
Element element = (Element)iterator.next();
if(class1Id.equalsIgnoreCase(element.getAttributeValue("id"))) ...{
class1Element = element;
break;
}
}while(iterator.hasNext());

if(class1Element!=null) ...{
Iterator iter = class1Element.getChildren().iterator();
do ...{
Element element = (Element)iter.next();
if(class2Id.equalsIgnoreCase(element.getAttributeValue("id"))) ...{
class2Element = element;
break;
}
}while(iter.hasNext());

if(class2Element!=null) ...{
Iterator iter2 = class2Element.getChildren().iterator();
do ...{
Element element = (Element)iter2.next();
ProductClass product = new ProductClass(element.getAttributeValue("id"),element.getAttributeValue("className"));
products.add(product);
}while(iter2.hasNext());
}
return (ProductClass[])products.toArray(new ProductClass[0]);
}
else return null;
}
}


?xml version="1.0" encoding="UTF-8"?>
!DOCTYPE class SYSTEM "product.dtd" >
class>
class1 className="电脑配件" id="1">
class2 className="内存" id="1">
class3 id="1" className="kingmax">/class3>
class3 id="2" className="kingston">/class3>
class3 id="3" className="samsung">/class3>
class3 id="4" className="hydadi">/class3>
class3 id="5" className="ibm">/class3>
/class2>
class2 className="硬盘" id="2">
class3 id="6" className="hithait">/class3>
class3 id="7" className="IBM">/class3>
class3 id="8" className="samsung">/class3>
class3 id="9" className="westdata">/class3>
/class2>
/class1>

class1 className="食品配件" id="2">
class2 className="汉堡包" id="1">
class3 id="1" className="麦当劳">/class3>
class3 id="2" className="肯得基">/class3>
class3 id="3" className="罗杰丝">/class3>
/class2>
class2 className="饮料" id="2">
class3 id="4" className="cocacola">/class3>
class3 id="5" className="sprite">/class3>
class3 id="6" className="coffee">/class3>
class3 id="7" className="water">/class3>
/class2>
/class1>
/class>


?xml version="1.0" encoding="GB2312" ?>
!ELEMENT class (class1+)>
!ELEMENT class1 (class2+)>
!ATTLIST class1 className NMTOKEN #REQUIRED>
!ATTLIST class1 id NMTOKEN #REQUIRED>
!ELEMENT class2 (class3+)>
!ATTLIST class2 className NMTOKEN #REQUIRED>
!ATTLIST class2 id NMTOKEN #REQUIRED>
!ELEMENT class3 EMPTY>
!ATTLIST class3 className NMTOKEN #REQUIRED>
!ATTLIST class3 id NMTOKEN #REQUIRED>

JSP:
(1)getClass.jsp 充当业务层供ajax调用
%@ page contentType="text/html; charset=gb2312"%>
%@ page import="com.ajaxlab.ajax.*"%>
%
String class1Id = request.getParameter("class1Id");
String class2Id = request.getParameter("class2Id");
if("".equals(class1Id)) class1Id = null;
if("".equals(class2Id)) class2Id = null;
ClassService service = new ClassService();
if((class1Id!=null)(class2Id==null)) ...{
ProductClass[] classes = service.getAllClass2ById(class1Id);
if(classes!=null) ...{
for(int i=0;iclasses.length;i++) ...{
out.print(classes[i].getId()+","+classes[i].getClassName()+"|");
}
}
}
else if((class1Id!=null)(class1Id!=null)) ...{
ProductClass[] classes = service.getAllClass3ById(class1Id,class2Id);
if(classes!=null) ...{
for(int i=0;iclasses.length;i++) ...{
out.print(classes[i].getId()+","+classes[i].getClassName()+"|");
}
}
}
%>

(2)divmenu.jsp
%@ page contentType="text/html; charset=gb2312"%>
%@ page import="com.ajaxlab.ajax.*"%>
!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
html>
head>
script type="text/javascript" src="ajax_func.js" >/script>
script type="text/javascript">

function doChange() ...{
var f = document.forms[0];
send_request("GET","getClass.jsp?class1Id="+f.select11.value+"class2Id=",null,"TEXT",populateClass2);
}
function doChange2() ...{
var f = document.forms[0];
send_request("GET","getClass.jsp?class1Id="+f.select11.value+"class2Id="+f.select12.value,null,"TEXT",populateClass3);
}
function populateClass2()...{
var f=document.forms[0];
if(http_request.readystate==4)...{
if(http_request.status==200)...{
var list=http_request.responseText;
var classList=list.split("|");
f.select12.options.length=1;
for(var i=0;iclassList.length-1;i++)...{
var temp=Trim(classList[i]).split(",");
f.select12.add(new Option(temp[1],temp[0]));
}
}
}
}

function populateClass3()...{
var f=document.forms[0];
if(http_request.readystate==4)...{
if(http_request.status==200)...{
var list=http_request.responseText;
var classList=list.split("|");
f.select13.options.length=1;
for(var i=0;iclassList.length-1;i++)...{
var temp=Trim(classList[i]).split(",");
f.select13.add(new Option(temp[1],temp[0]));
}
}
}
}
function LTrim(str)
...{
var whitespace = new String(" ");
var s = new String(str);
if (whitespace.indexOf(s.charAt(0)) != -1)
...{
var j=0, i = s.length;
while (j i whitespace.indexOf(s.charAt(j)) != -1)
...{
j++;
}
s = s.substring(j, i);
}
return s;
}
function RTrim(str)
...{
var whitespace = new String(" ");
var s = new String(str);
if (whitespace.indexOf(s.charAt(s.length-1)) != -1)
...{
var i = s.length - 1;
while (i >= 0 whitespace.indexOf(s.charAt(i)) != -1)
...{
i--;
}
s = s.substring(0, i+1);
}
return s;
}
function Trim(str)
...{
return RTrim(LTrim(str));
}
/script>
%
ClassService service = new ClassService();
ProductClass[] classes = service.getAllClass1();
%>
meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
title>Insert title here/title>
/head>
body>center>
form name="classForm" method="post" action="">
select name="select11" id="select11" onchange="doChange(this.value)">
option value="">请选择分类一/option>
%
for(int i=0;iclasses.length;i++) ...{
out.println("option value='"+classes[i].getId()+"'>"+classes[i].getClassName()+"/option>");
}
%>
/select>

select name="select12" id="select12" onchange="doChange2(this.value)">
option value="">请选择分类二/option>
/select>

select name="select13" id="select13">
option value="">请选择分类三/option>
/select>
/form>
/center>/body>
/html>