function getXHR(){

			if(window.XMLHttpRequest){

				return new XMLHttpRequest();

			}else{

				try{

					return new ActiveXObject("Msxml2.XMLHTTP.6.0");

				}catch(e1){

					try{

						return new ActiveXObject("Msxml2.XMLHTTP.3.0");

					}catch(e2){

						throw new Error("xmt is not support!");

					}

				}

			}

		}

		function XHR(){

			this.xhr=getXHR();

		}

		XHR.prototype.getJsonByGet=function(url){

			var XHRequest=this.xhr;

			XHRequest.open("GET",url);

			XHRequest.onreadystatechange=function(){

				if(XHRequest.readyState===4 && XHRequest.status===200){

					var type=XHRequest.getResponseHead("Content-Type");

					if(type.match(/^text/))

						return JSON.parse(XHRequest.responseText);

				}

			}

			XHRequest.send(null);

		}

		XHR.prototype.getJsonByPost=function(url,postJson){

			var XHRequest=this.xhr;

			XHRequest.open("POST",url);

			XHRequest.setRequestHeader("Content-Type","text/plain;charset=UTF-8");

			XHRequest.onreadystatechange=function(){

				if(XHRequest.readyState===4 && XHRequest.status===200){

					var type=XHRequest.getResponseHead("Content-Type");

					if(type.match(/^text/))

						return JSON.parse(XHRequest.responseText);

				}

			}

			XHRequest.send(JSON.stringify(postJson));

		}