/*AJAX对象封装*/
var com=new Object();
com.trs=new Object();
com.trs.cds=new Object();
com.trs.cds.js=new Object();
com.trs.cds.js.ajax=new Object();//命名空间

//请求状态
com.trs.cds.js.ajax.READY_STATE_UNINITIALIZED=0;
com.trs.cds.js.ajax.READY_STATE_LOADING=1;
com.trs.cds.js.ajax.READY_STATE_LOADED=2;
com.trs.cds.js.ajax.READY_STATE_INTERACTIVE=3;
com.trs.cds.js.ajax.READY_STATE_COMPLETE=4;
//构造函数
com.trs.cds.js.ajax.AjaxRequest=function(){
//申请XMLHttpRequest
this.initRequest=function(){
	if(typeof window.XMLHttpRequest!='undefined'){// branch for native XMLHttpRequest object
		try{
			this.req = new XMLHttpRequest();
		}
		catch(e){
			this.req = false;
		}
	}
	else if(window.ActiveXObject){ // branch for IE/Windows ActiveX version
		try{
			this.req = new ActiveXObject("Msxml2.XMLHTTP");
		}
		catch(e){
			try{
				this.req = new ActiveXObject("Microsoft.XMLHTTP");
			}
			catch(e){
				this.req = false;
			}
		}
	}
};
	
	
//返回XML对象
this.getResponseXML=function(){
	if(this.req)return this.req.responseXML;
};

//返回Text对象
this.getResponseText=function(){
	if(this.req)return this.req.responseText;
};

//设置URL
this.setUrl=function(url){
	this.url=(url)?url:"";
};

//设置Method:取值范围有GET,POST,HEAD等
this.setMethod=function(method){
	this.method=(method)?method:'GET';
};

//设置内容加载完成的执行体,如setOnLoad("a('abc')"),将在请求完成时执行a('abc');这样的子句
this.setOnLoad=function(onload){
	this.onload=onload;
	if(this.onload.indexOf('(')==-1){
		this.onload=this.onload+"()";
	}
};

//设置同步或者异步:true,异步;flase,同步
this.setAasynchronous=function(asy){
	this.asynchronous=(asy)?asy:true;
};

//设置POST方式下提交的参数
this.setParams=function(params){
	this.params=(params)?params:null;
};

//设置在内容加载完成前的执行体
//@see setOnLoad
this.setBeforeLoad=function(beforeload){
	this.beforeload=beforeload;
	if(this.beforeload!=null&&this.beforeload.indexOf('(')==-1){
		this.beforeload=this.beforeload+"()";
	}
};

//设置在内容加载时出错的执行体
//@see setOnLoad
this.setOnError=function(error){
	this.onerror=(error)?error:this.onerror;
	if(onerror!=null&&this.onerror.indexOf('(')==-1){
		this.onerror=this.onerror+"()";
	}
};

//设置请求的头信息
this.setRequestHeader=function(key,value){
	if(this.req){
		this.req.setRequestHeader(key,value);		
	}
};

//加载内容
this.load=function(){
	if(this.req){
		try{
			var loader=this;
			if(this.asynchronous){//异步
				this.req.onreadystatechange=function(){
					loader.onReadyState.call(loader);
				}
				this.req.open(this.method,this.url,true);	
				if(this.method.toLowerCase()=="post")this.req.setRequestHeader("content-type","application/x-www-form-urlencoded");	
				this.req.send(this.params);
			}
			else{//同步
				this.req.open(this.method,this.url,false);
				if(this.method.toLowerCase()=="post")this.req.setRequestHeader("content-type","application/x-www-form-urlencoded");	
				loader.onReadyState().call(loader);
				this.req.send(this.params);
			}
  	}
		catch (err){
			eval(this.error);
		}
	}
};

//请求状态变化时的执行体
this.onReadyState=function(){
	var status=this.req.readyState;
  if (status==com.trs.cds.js.ajax.READY_STATE_COMPLETE){//加载完成
		var httpStatus=this.req.status;
		if(httpStatus==200 || httpStatus==0){//正确返回
			eval(this.onload);
		}
		else{
			eval(this.error);
		}
	}
	else{//加载未完成
		if(this.beforeload){
			eval(this.beforeload);
		}
	}
};

//缺省出错执行体
this.defaultError=function(){
	alert("error fetching data!"
	+"\n\nreadyState:"+this.req.readyState
	+"\nstatus: "+this.req.status
	+"\nheaders: "+this.req.getAllResponseHeaders());
};
  
this.url=null;
this.req=false;
this.method='GET';
this.asynchronous=true;
this.params=null;
this.onload=null;
this.beforeload=false;
this.onerror="this.defaultError()";
this.initRequest();
};