最近正在拜读《Ajax in Action》这本书，运用书中知识，结合.net，写了这篇用.net 处理xmlHttp发送异步请求的文章。

我们要达到的目的是点击按钮，获得服务器的当前时间，aspx的html如下：

            Html
            <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs"
            Inherits="Linkedu.Web.WebWWW.Default" %>
           
                        "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
           
            http://www.w3.org/1999/xhtml" >
           
           
           
           
           
           
           
           
           
           
           
           
            用Post方式获得服务器的当前时间
           
            用Get方式获得服务器的当前时间
           
           

           
           
           
           
 

要用javascript. 发送xmlHttp 请求必须解决的问题是跨浏览器的支持。我们把xmlHttp的发送封装在一个javascript对象中，同时在这个对象中解决了跨浏览器支持的问题。代码如下：

            xmlHttp对象
           
            /**//*
            url-loading object and a request queue built on top of it
            */
           
            /**//* namespacing object */
            var net=new Object();
           
            net.READY_STATE_UNINITIALIZED=0;
            net.READY_STATE_LOADING=1;
            net.READY_STATE_LOADED=2;
            net.READY_STATE_INTERACTIVE=3;
            net.READY_STATE_COMPLETE=4;   
           
            /**//*--- content loader object for cross-browser requests ---*/
            net.xmlHttp=function(url, onload, params, method, contentType, onerror){
            this.req=null;
            this.onload=onload;
            this.onerror=(onerror) ? onerror : this.defaultError;
            if(typeof(method) == "undefined" || method == null)
            {
            method = "POST";
            }
            this.loadXMLDoc(url, params, method, contentType);
            }
           
            net.xmlHttp.prototype.loadXMLDoc=function(url, params, method, contentType){
            if (!method){
            method="GET";
            }
            if (!contentType && method=="POST"){
            contentType='application/x-www-form-urlencoded';
            }
            if (window.XmlHttpRequest){
            this.req=new XmlHttpRequest();
            } else if (window.ActiveXObject){
            this.req=new ActiveXObject("Microsoft.xmlHttp");
            }
            if (this.req){
            try{
            var loader=this;
            this.req.onreadystatechange=function(){
            net.xmlHttp.onReadyState.call(loader);
            }
            this.req.open(method,url,true);
            if (contentType){
            this.req.setRequestHeader('Content-Type', contentType);
            }
            this.req.send(params);
            }catch (err){
            this.onerror.call(this);
            }
            }
            }   
           
            net.xmlHttp.onReadyState=function(){
            var req=this.req;
            var ready=req.readyState;
            if (ready==net.READY_STATE_COMPLETE){
            var httpStatus=req.status;
            if (httpStatus==200 || httpStatus==0){
            this.onload.call(this);
            }else{
            this.onerror.call(this);
            }
            }
            }
           
            net.xmlHttp.prototype.defaultError=function(){
            alert("error fetching data!"
            +"\n\nreadyState:"+this.req.readyState
            +"\nstatus: "+this.req.status
            +"\nheaders: "+this.req.getAllResponseHeaders());
            }
           
 

下面开始写发送xmlHttp请求的代码：

            default.js
            //全局xmlHttp对象
            var cobj;
           
            /**//* Post begin*/
            //绑定Post发送xmlHttp事件到btnTestPost
            function loadTestPost()
            {
            var iobj = document.getElementById("btnTestPost");
            //btnTestPost按钮监听的绑定
            var clickRouter=new jsEvent.EventRouter(iobj,"onclick");
            clickRouter.addListener(btnTestPostClick);
            }
            function btnTestPostClick()
            { // open参数 url, onload, params, method, contentType, onerror
            cobj = new net.xmlHttp("DefaultHandler.ashx",dealResult, "", "POST");
            }
            /**//* Post end*/
           
           
            /**//* Get begin*/
            //绑定Get发送xmlHttp事件到btnTestGet
            function loadTestGet()
            {
            var iobj = document.getElementById("btnTestGet");
            //btnTestGet按钮监听的绑定
            var clickRouter=new jsEvent.EventRouter(iobj,"onclick");
            clickRouter.addListener(btnTestGetClick);
            }
            function btnTestGetClick()
            { // open参数 url, onload, params, method, contentType, onerror
            cobj = new net.xmlHttp("DefaultHandler.ashx?T=1",dealResult, null, "GET");
            }
            /**//* Get end*/
           
           
           
            function dealResult()
            {
            var dobj = document.getElementById("divResult");
            dobj.innerHTML = cobj.req.responseXML.text;
            }
           
           
            window.onload = function()
            {
            //绑定Post发送xmlHttp事件到btnTestPost
            loadTestPost();
            //绑定Get发送xmlHttp事件到btnTestGet
            loadTestGet();
            };
           
 

最后是.net处理xmlHttp的代码：

            .net 处理xmlHttp请求
           
            public class DefaultHandler : IHttpHandler
            {
            protected XmlDocument _xmlResult;
           
            public void ProcessRequest(HttpContext context)
            {
            if (context.Request["T"] != null)
            {//GET xmlhttp测试
            context.Response.ContentType = "text/xml";
            XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.LoadXml(string.Format(@"GET:{0}", System.DateTime.Now));
            xmlDoc.Save(context.Response.OutputStream);
            context.Response.End();
            }
            else
            {//POST xmlhttp测试
            context.Response.ContentType = "text/xml";
            XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.Load(context.Request.InputStream);
            if (xmlDoc.DocumentElement.Name == "T")
            {
            xmlDoc.LoadXml(string.Format(@"POST:{0}", System.DateTime.Now));
            xmlDoc.Save(context.Response.OutputStream);
            context.Response.End();
            }
            }
            }
           
            public bool IsReusable
            {
            get
            {
            return false;
            }
            }
            }