var XMLHttp = {
    _objPool: [],
    _getInstance: function (){
        for (var i = 0; i < this._objPool.length; i ++){
            if (this._objPool[i].readyState == 0 || this._objPool[i].readyState == 4){
                return this._objPool[i];
            }
        }
        this._objPool[this._objPool.length] = this._createObj();
        return this._objPool[this._objPool.length - 1];
    },
	 _createObj: function (){
        if (window.XMLHttpRequest){
            var objXMLHttp = new XMLHttpRequest();
        }
        else{
            var MSXML = ['MSXML2.XMLHTTP.5.0', 'MSXML2.XMLHTTP.4.0', 'MSXML2.XMLHTTP.3.0', 'MSXML2.XMLHTTP', 'Microsoft.XMLHTTP'];
            for(var n = 0; n < MSXML.length; n ++){
                try{
                    var objXMLHttp = new ActiveXObject(MSXML[n]);
                    break;
                }
                catch(e){
                	alert(e.message);
                }
            }
         }          
        if (objXMLHttp.readyState == null){
            objXMLHttp.readyState = 0;
            objXMLHttp.addEventListener("load", function (){
                    objXMLHttp.readyState = 4;
                    if (typeof objXMLHttp.onreadystatechange == "function"){
                        objXMLHttp.onreadystatechange();
                    }
                },  false);
        }
        return objXMLHttp;
    },
    sendReq: function (method, url, data, callback,requesttype){
        var objXMLHttp = this._getInstance();
        //save the arguments to fix a firefox bug.
        try{
        	objXMLHttp.callback=callback;
        	objXMLHttp.requesttype=requesttype;
        }catch(e){}
        try{
        	//cache 5 seconds
        	var random=parseInt((new Date).getTime()/(5*1000));
            if (url.indexOf("?") > 0){
                url += "&randnum=" + random;
            } else{
                url += "?randnum=" + random;
            }
            objXMLHttp.open(method, url, true);
            objXMLHttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded; charset=UTF-8');
            objXMLHttp.onreadystatechange = function (){
                if (objXMLHttp.readyState == 4 && (objXMLHttp.status == 200 || objXMLHttp.status == 304))
                {
                	//check if there are errors happened.
                	var res=objXMLHttp.responseText;
                	if(res!=null){
	                	if(res.indexOf("error:")==0){
	                		alert(res.substring(6,res.length));
	                		return;
	                	}else{
	                		var arr=res.split("\r\n");
	                		for(var i=0;i<arr.length;i++){
	                			if(arr[i].indexOf("top.location.href=\"http://qiye.163.com/admin.jsp")==0){
	                				eval(arr[i]);
		                			return;	
	                			}
	                		}
	                	}
                	}
                    if(objXMLHttp.callback){
	                    objXMLHttp.callback(objXMLHttp,objXMLHttp.requesttype);
                    }else{
                    	callback(objXMLHttp,requesttype);
                    }
                }
            }
            objXMLHttp.send(data);
        }
        catch(e){
            alert(e.message);
        }
    }
};