使用Ajax与后台服务器进行交互时，返回的数据并不是都是文本类型，也有xml类型、Jason类型等。
本篇文章主要讲解对返回的xml类型数据进行解析。
示例解析：
我们要做到示例是，有两个下拉选框，第一个下拉框是省份，第二个是所选省下相对应的市。当省份改变时，相对应的市也应改变。例如，当选择广东省时，地区项应包括：广州、深圳、佛山、汕头。
示例图示：
源代码：
jsp页面文件：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getcontextpath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'select.jsp' starting page</title>
<Meta http-equiv="Content-Type" content="text/html;charset=utf-8">
<script type="text/javascript">
<!--
var xmlHttp;
function createXmlHttp() {
if(window.XMLHttpRequest) {
xmlHttp = new XMLHttpRequest();
} else if(window.ActiveXObject) {
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
}
}
function updateSelect() {
var selected = document.getElementById("slt1").value;
createXmlHttp();
xmlHttp.onreadystatechange = processor;
var url = "createXml?selected=" + selected;
xmlHttp.open("POST",url,true);
xmlHttp.send(null);
}
function processor() {
var result;
if(xmlHttp.readyState == 4) {
if(xmlHttp.status == 200) {
//注意此处是xmlHttp.responseXML而不是xmlHttp.responseText
//获取节点名为city的所有节点
result = xmlHttp.responseXML.getElementsByTagName("city");
var slt2 = document.getElementById("slt2");
//将二级下拉框中的所有选项清空
while(slt2.options.length>0) {
slt2.removeChild(slt2.childNodes[0]);
}
//根据返回节点数目构造下拉选项
for(var i=0; i<result.length; i++) {
var option = document.createElement("option");
//根据节点名称获取城市名称，并赋值
option.text = result[i].getElementsByTagName("cityname")[0].firstChild.nodeValue;
//根据节点名称获取城市值，并赋值
option.value = result[i].getElementsByTagName("cityvalue")[0].firstChild.nodeValue;
//千万不要忘记将该节点加入到下拉框父节点中
slt2.options.add(option);
}
}
}
}
-->
</script>
</head>
<body>
<form>
省份：
<select id="slt1" onChange="updateSelect()">
<option value="1">河南省</option>
<option value="2">广东省</option>
</select>
地区：
<select id="slt2">
<option>请选择地方</option>
<option value="1">濮阳</option>
<option value="2">安阳</option>
<option value="3">南阳</option>
<option value="4">郑州</option>
</select>
</form>
</body>
</html>
Servlet源代码：
package com.zyh.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.servletexception;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class CreateXml extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request,HttpServletResponse response)
throws servletexception,IOException {
//这里一定要设置为xml类型的文件，而不是text/html
response.setContentType("text/xml;charset=utf-8");
response.setCharacterEncoding("utf-8");
String selected = request.getParameter("selected");
PrintWriter out = response.getWriter();
out.println("<response>");
if(selected.equals("1")) {
out.println("<city>");
out.println("<cityname>濮阳</cityname>");
out.println("<cityvalue>1</cityvalue>");
out.println("</city>");
out.println("<city>");
out.println("<cityname>安阳</cityname>");
out.println("<cityvalue>2</cityvalue>");
out.println("</city>");
out.println("<city>");
out.println("<cityname>南阳</cityname>");
out.println("<cityvalue>3</cityvalue>");
out.println("</city>");
out.println("<city>");
out.println("<cityname>郑州</cityname>");
out.println("<cityvalue>4</cityvalue>");
out.println("</city>");
} else {
out.println("<city>");
out.println("<cityname>广州</cityname>");
out.println("<cityvalue>1</cityvalue>");
out.println("</city>");
out.println("<city>");
out.println("<cityname>深圳</cityname>");
out.println("<cityvalue>2</cityvalue>");
out.println("</city>");
out.println("<city>");
out.println("<cityname>佛山</cityname>");
out.println("<cityvalue>3</cityvalue>");
out.println("</city>");
out.println("<city>");
out.println("<cityname>汕头</cityname>");
out.println("<cityvalue>4</cityvalue>");
out.println("</city>");
}
out.println("</response>");
out.flush();
out.close();
}
}