详细地址和最新代码请看google code上的：http://code.google.com/p/coos/source/browse/trunk/coos/WebRoot/scripts/coos.ext.ajax.js
/**
* ajax框架类，提供五个对外接口.
* 一般情况下都是异步请求(同步用ajax没有意义)asynchronous可以不用传入
* 第三个参数extend为callbackFunction的扩展参数,可以不传入，后面有其他参数同时没有扩展参数可以传入null
* coos.ajax.get(url,callbackFunction,extend,asynchronous)
* coos.ajax.post(url,callbackFunction,formElement,extend,encode,asynchronous)
* coos.ajax.postText(url,callbackFunction,formElement,extend,asynchronous)
* coos.ajax.postUnencode(url,callbackFunction,formElement,extend,asynchronous)
* coos.ajax.jsonp(url,callbackFunction,responseName,extend)
*/
coos.ajax = function()
{
this.version = "1.0";
};

/**
* 创建XMLHttpRequest工厂类
*/
coos.ajax.createRequest = function()
{
var objXMLHttp = null;

if (window.XMLHttpRequest)
{
objXMLHttp = new XMLHttpRequest();
   
if (objXMLHttp.overrideMimeType)
{
objXMLHttp.overrideMimeType('text/xml');
}
}
else
{
    var MSXML = ['Msxml2.XMLHTTP', 'Microsoft.XMLHTTP', 'MSXML2.XMLHTTP.5.0', 'MSXML2.XMLHTTP.4.0', 'MSXML2.XMLHTTP.3.0'];
   
    for(var n = 0; n < MSXML.length; n++)
    {
        try
        {
            objXMLHttp = new ActiveXObject(MSXML[n]);       
            break;
        }
        catch(e) {}
    }
}

  return objXMLHttp;
};

/**
* 本域get请求
* @param url 请求相对路径
* @param callbackFunction 回调函数
* @param extend 回调函数扩展参数(json格式)
* @param asynchronous 是否为异步请求，默认为true
* @example
function testGet()
{
var url = "ajax_test.action?type=localhost";
coos.ajax.get(url,getCallback,{test1:'aaa1',test2:'bbb1'});
//coos.ajax.get(url,function(test1,test2,responseText){alert(responseText);alert(test1);},{test1:'aaa1',test2:'bbb1'});
}
function getCallback(responseText,test1,test2)
{
alert("getCallback responseText = " + responseText);
alert("getCallback message = " + responseText.toJson().message);
alert("getCallback test1 = " + test1);
}
*/
coos.ajax.get = function(url,callbackFunction,extend,asynchronous)
{
var http_request = coos.ajax.createRequest();
coos.ajax.bindResponse (http_request,callbackFunction,extend);
url = coos.url.random(url);
asynchronous = asynchronous || true;
http_request.open ("GET", url, asynchronous);

http_request.send (null);

return false;
};

/**
* post请求
* @param url 请求相对路径
* @param formElement 表单对象或表单id
* @param callbackFunction 回调函数
* @param extend 回调函数扩展参数(json格式)
* @param encode 编码方式text，unencode，其他，默认采用通用的两次encodeURIComponent
* 后台解码：java.net.URLDecoder.decode(request.getParameter("name"), "UTF-8″);
* @param asynchronous 是否为异步请求，默认为true
* @example
function testPost()
{
var url = "../getData?action=getPostData";
var form = coos.$id("post_add");
//no extend param
//coos.ajax.post(url,postCallback,"post_add");

//extend json object
var id = form.id;
//coos.ajax.post(url,postCallback,"post_add",{test1:id,test2:'bbb3'});

//extend jsonStr
var jsonStr = "{test1:'" + id + "',test2:'bbb3'}"
var ext = jsonStr.toJson();
//var ext = eval('(' + json + ')');
coos.ajax.post(url,postCallback,"post_add",ext);

}
function postCallback(responseText,test1,test2)
{
//{success:true,action:'getPostData',message:'test message'}
alert("postCallback responseText = " + responseText);
alert("postCallback is success = " + responseText.toJson().success);
alert("postCallback message = " + responseText.toJson().message);
alert("postCallback test1 = " + test1);
alert("postCallback test2 = " + test2);
}
<form action="" id="post_add" name="post_add" method="post" onsubmit="return false;">
<textarea name="message" id="message">test message 测试中文</textarea>
<input type="button" id="subBtn" value="submit" onclick="testPost()" />
</form>
*/
coos.ajax.post = function(url,callbackFunction,formElement,extend,encode,asynchronous)
{
var http_request = coos.ajax.createRequest();

coos.ajax.bindResponse(http_request,callbackFunction,extend);
url = coos.url.random(url);
asynchronous = asynchronous || true;
formElement = coos.$obj(formElement);
//获取表单内容字符串，转换比较多，需要时间比较久
var requireString = coos.ajax.parseParameteres(formElement,encode);
//获取字符串后再打开链接
http_request.open("POST", url, asynchronous);

http_request.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
http_request.setRequestHeader("encoding","utf-8");
http_request.setRequestHeader("Content-length", requireString.length);
//在win2000下的ie6.0会导致很慢
//jquery mootools ext中都没有此项设置,prototype-1.6下说明为了兼容低版本的Mozilla浏览器才设置的
//http_request.setRequestHeader("Connection","close");

//Mozilla浏览器post方法不能用send(null)没有内容必须用send("")
if(requireString == null){requireString = "";}
http_request.send(requireString);

return false;
};

/**
* 文本形式post请求(去掉换行符和html标签)
*/
coos.ajax.postText = function(url,callbackFunction,formElement,extend,asynchronous)
{
coos.ajax.post(url,callbackFunction,formElement,extend,"text",asynchronous);
};

/**
* 不进行编码，直接提交表单内容
*/
coos.ajax.postUnencode = function(url,callbackFunction,formElement,extend,asynchronous)
{
coos.ajax.post(url,callbackFunction,formElement,extend,"unencode",asynchronous);
};

/**
* 跨域请求
* @param url 请求路径,跨域要完整的路径，本域可以是相对路径
* @param callbackFunction 回调函数
* @param responseName 服务端返回的变量名称,会把值自动附加到url参数中，后台可以获取到
* @param extend 回调函数扩展参数(json格式)
* @example
function testJsonp()
{
var url = "http://zhengdz.iap111.com:8080/coos/coos/ajax_test.action?type=remote";
coos.ajax.jsonp(url,jsonpCallback,"remote_request",{test1:'aaa2',test2:'bbb2'});
}
function jsonpCallback(responseText,test1,test2)
{
alert("jsonpCallback responseText = " + responseText);
alert("jsonpCallback message = " + responseText.toJson().message);
alert("jsonpCallback test1 = " + test1);
}
*/
coos.ajax.jsonp = function(url,callbackFunction,responseName,extend)
{
var script = document.createElement("script");
script.id = "coos_jsonp_" + responseName;

    if(script.addEventListener)
    {
script.addEventListener("load", function(){
coos.ajax.jsonp.callbackHandle(callbackFunction,responseName,extend);
}, false);
    }  
else if(script.attachEvent)
{
script.attachEvent("onreadystatechange",function(){
var target = window.event.srcElement;
if(target.readyState == "loaded")
{
coos.ajax.jsonp.callbackHandle(callbackFunction,responseName,extend);
}
});
}
//通过url参数传递给后台，后台通过request获取responseName参数值获得传递过去的变量名
if(responseName)
{
url = coos.url.addAttribe("responseName",responseName,url);
}
url = coos.url.random(url);
script.src = url;
coos.$head().appendChild(script);
};

/**
* 跨域请求回调处理函数,在script脚本onload完成后执行
* @param callbackFunction 回调函数
* @param extend 回调函数扩展参数(json格式)
* @param responseName 服务端返回的变量名称
*/
coos.ajax.jsonp.callbackHandle = function(callbackFunction,responseName,extend)
{
try
{
var responseText = eval(responseName);
//非字符串类型转换为json字符串类型
if(typeof(responseText) == "object")
{
responseText = coos.json.toJSONString(responseText);
}

callbackFunction["responseText"] = responseText;
var args = [];
args.push(responseText);
if(typeof(extend) == "object" && extend !== null)
{
for (var property in extend)
{
//绑定property,可以通过函数本身调用
callbackFunction[property] = extend[property];
//把参数值按照顺序放入到数组中，通过apply传入
args.push(extend[property]);
}
}
//动态调用函数，把参数值数组传入
callbackFunction.apply(this,args);
//移除本次请求的script脚本，避免脚本不断增加
coos.$head().removeChild(coos.$id("coos_jsonp_" + responseName));
}
catch(e)
{
//alert("实际错误消息为：" + e.message + "\n错误类型字符串为：" + e.name);
}
};

/**
* escape字符串，并对特殊符号作处理
* @param str 需要处理的字符串
* @param encode 编码方式：unencode,text,other
*/
coos.ajax.encode = function(str,encode)
{
//不传入编码类型则默认编码
if(typeof(encode) == "undefined"){encode = "encode";}
//str为空或不用编码则直接返回
if (str == null || str == "" || encode=="unencode")
{
return str;
}
var value = "";
//value编码采用和jquery一样的处理方式
//后台解码：java.net.URLDecoder.decode(request.getParameter("name"), "UTF-8″);
if(encode == "text")
{
value = str.replace(/\n|\r|\r\n/g,"");//去掉换行符号
value = value.replace(/<\/?.+?>/g,"");//去掉HTML标签
value = encodeURIComponent(encodeURIComponent(value)).replace(/%20/g, "+");
}
else
{
value = encodeURIComponent(encodeURIComponent(str)).replace(/%20/g, "+");
}
/*
//自定义的方法，由于后台没有统一的解码方式，不推荐使用
else
{
value = escape(str);
//替换+号为%2B
value = value.replace(/\+/g, "%2B");
//替换%号为%25如"%u2a2a dfd %u1f1f";替换后为%25u2a2a dfd %25u1f1f
value = value.replace(/%u([0-9A-F]{4})/ig,function(word){return escape(word);});
}
//java后端没有直接的解码函数，自定义方法为：
public static String unescape (String str)
{
if (str == null)
return null;

String regEx="%u([0-9A-F]{4})";
Pattern p=Pattern.compile(regEx);
Matcher m=p.matcher(str);

StringBuffer sb = new StringBuffer();

while (m.find ())
{
String group = m.group ().substring(2);
m.appendReplacement(sb, String.valueOf((char)(Integer.parseInt(group,16))));
}

m.appendTail(sb);

return sb.toString();
}
*/
return value;
};

/**
* 获取表单内容字符串,表单只有input select textarea 三种类型
* @param formElement 表单对象或id
*/
coos.ajax.parseParameteres = function(formElement,encode)
{
formElement = coos.$obj(formElement);
var rs = "";
rs += coos.ajax.getValue(formElement.getElementsByTagName("input"),"input",encode);
rs += coos.ajax.getValue(formElement.getElementsByTagName("select"),"select",encode);
rs += coos.ajax.getValue(formElement.getElementsByTagName("textarea"),"textarea",encode);
return rs;
};

/**
* 获取单个表单元素的内容
* @param elements 表单元素对象
* @param type 表单元素类型
*/
coos.ajax.getValue = function(elements,type,encode)
{
var len = elements.length;
if(len == 0)return "";
var s = "";

if(type == "input")
{
for (var i = 0; i < len; i++)
{
var obj = elements[i];

if (obj.type == "hidden")
{
s += obj.name + "=" + coos.ajax.encode(obj.value,encode) + "&";
}
else if (obj.type == "text")
{
s += obj.name + "=" + coos.ajax.encode(obj.value,encode) + "&";
}
else if (obj.type == "password")
{
s += obj.name + "=" + coos.ajax.encode(obj.value,encode) + "&";
}
else if (obj.type == "checkbox")
{
if (obj.checked)
{
s += obj.name + "=" + coos.ajax.encode(obj.value,encode) + "&";
}
}
else if (obj.type == "radio")
{
if (obj.checked)
{
s += obj.name + "=" + coos.ajax.encode(obj.value,encode) + "&";
}
}
}
}
else if(type == "textarea")
{
for (var i = 0; i < len; i++)
{
var obj = elements[i];

s += obj.name + "=" + coos.ajax.encode(obj.value,encode) + "&";
}
}
else if(type == "select")
{
for (var i = 0; i < len; i++)
{
var obj = elements[i];

if (obj.type == "select")
{
if (obj.selectedIndex > -1)
s += obj.name + "=" + coos.ajax.encode(obj.options[obj.selectedIndex].value,encode) + "&";
}
else if (obj.type == "select-one")
{
if (obj.selectedIndex > -1)
s += obj.name + "=" + coos.ajax.encode(obj.options[obj.selectedIndex].value,encode) + "&";
}
}
}
return s;
};

/**
* 绑定ajax请求回调函数，属于内部函数
*/
coos.ajax.bindResponse = function(http_request,callbackFunction,extend)
{
if(typeof(callbackFunction) != "function")
{
alert("请传入回调函数!");
return false;
}
var responseText = "";
var isTiemout = false;
//设定5秒后请求超时
setTimeout(function(){isTimeout = true;},5000);
http_request.onreadystatechange = function()
{
if (http_request.readyState == 4 && !isTiemout)
{
if (http_request.status == 200)
{
responseText = http_request.responseText;
try
{
//绑定property,可以通过函数本身调用
callbackFunction["responseText"] = responseText;
var args = [];
//把responseText放入第一个位置，通过apply传入
args.push(responseText);
if(typeof(extend) == "object" && extend !== null)
{
for (var property in extend)
{
//绑定property,可以通过函数本身调用
callbackFunction[property] = extend[property];
//把参数值按照顺序放入到数组中，通过apply传入
args.push(extend[property]);
}
}
//动态调用函数，把参数值数组传入
callbackFunction.apply(this,args);
//eval(callbackFunction);

//为避免内存泄漏，清理文档
try{http_request = null;}catch(e){}
}
catch(e)
{
alert("实际错误消息为：" + e.message + "\n错误类型字符串为：" + e.name);
}
}
else
{
var status = http_request.status;
switch (status)
{
case 403:
alert("你请求的页面禁止访问!");
break;
case 404:
alert("你请求的页面不存在!");
break;
case 500:
alert("你请求的页面服务器内部错误!");
break;
case 502:
alert("Web服务器收到无效的响应!");
break;
case 503:
alert("服务器繁忙，请稍后再试!");
break;
default:
alert("你请求的页面遇到问题，操作失败!错误代码:" + status);
break;
}
}
}

};
};