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    AJAX级联下拉框的简单实现案例

    需要的JAVA类

    复制代码 代码如下:

    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(" /t/n/r");
        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(" /t/n/r");
        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>

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    AJAX级联下拉框的简单实现案例 AJAX,级联,下拉,框,的,简单,