AJAX级联下拉框的简单实现案例

(编辑：jimmy 日期: 2024/11/28 浏览：3 次 )

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>

<?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;i<classes.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;i<classes.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="/UploadFiles/2021-04-02/ajax_func.js"><script type="text/javascript">

<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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