/*
ContentLoader对象
参数说明：
		url:请求的地址
	    onload:处理服务器发回请求的方法
	    method:请求的方式 POST 或 GET
		params:当请求的方式为POST时的参数，服务器端的程序可以通过Request.Form["username"]来获取
		onerror:发生错误的处理方法
作者：景爱辉
*/
var net = new Object();
net.ContentLoader = function(url,onload,method,params,onerror)
{
	this.url =url;
	this.req = null;
	this.onload = onload;
	this.method = (method)?method:'GET';
	this.params = params;
	this.onerror = (onerror)?onerror:this.defaultError;
	this.loadXmlDoc(url);
}
net.ContentLoader.prototype = 
{
	loadXmlDoc:function(url) 
	{
		if(window.XMLHttpRequest)
		{
			this.req = new XMLHttpRequest();
		}
		else if(window.ActiveXObject)
		{
			try 
			{ 
				this.req = new ActiveXObject("Msxml2.XMLHTTP"); 
			} 
			catch (e) 
			{ 
				try 
				{ 
					this.req = new ActiveXObject("Microsoft.XMLHTTP"); 
				} 
				catch (e)
				{ 
					this.onerror.call(this);
				} 
			} 
		}
		if(this.req)
		{
			try
			{
				var loader = this;
				this.req.onreadystatechange = function()
				{
					loader.onReadyState.call(loader);
				}
				if(this.method == 'GET')
				{
					this.req.open('GET',url,true);
					this.req.send(null);
				}
				else if(this.method == 'POST')
				{
					this.req.open('POST',url,true);
					this.req.setRequestHeader("CONTENT-TYPE","application/x-www-form-urlencoded");
					this.req.send(this.params);
				}
			}
			catch(err)
			{
				this.onerror.call(this);
			}
		}
	},
	onReadyState:function() 
	{
		var req = this.req;
		if(req.readyState == 4)
		{
			if(req.status == 200)
			{
				this.onload.call(this);
			}
			else
			{
				this.onerror.call(this);
			}
		}
	},
	defaultError:function() 
	{
		alert("读取数据发生错误！"+"\n\n readyState:"+this.req.readyState+"\n\n status:"+this.req.status);
	}
	
}

/*解析dropdownlist的函数（从服务端发过来的xml文件）*/
function fillDropDown()
{
	var xmlDoc = this.req.responseXML.documentElement;
	var xSel = xmlDoc.getElementsByTagName('selectElement')[0];
	var strFName = xSel.childNodes[0].firstChild.nodeValue;
	var strEName = xSel.childNodes[1].firstChild.nodeValue;
	var objDDL = document.forms.item(strFName).all.item(strEName);
	objDDL.options.length = 0;
	var begin = new Option('请选择','-1');
	objDDL.add(begin,-1);
	var xRows = xmlDoc.getElementsByTagName('entry');
	
	for(var i=0;i<xRows.length;i++)
	{
		var theText = xRows[i].childNodes[0].firstChild.nodeValue;
		var theValue = xRows[i].childNodes[1].firstChild.nodeValue;
		var option = new Option(theText,theValue);
		try
		{
			objDDL.add(option,null);
		}
		catch(e)
		{
			objDDL.add(option,-1);
		}
	}
}