// JScript 文件
/**
* XMLHttpRequest Object Pool
*
* @author legend <legendsky@hotmail.com>
* @link http://www.ugia.cn/?p=85
* @Copyright www.ugia.cn
*/ 


//connctionPool主要的作用是首次建立XMLHttpRequest对象时，先set一个对象数组，在状态是完成4，或0闭置的情况下，可用。
var XMLHttpUser = {
	_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];
			}
		}
		
		// IE5中不支持push方法
		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)
				{
				}
			}
		} 
	
		// mozilla某些版本没有readyState属性
		if (objXMLHttp.readyState == null)
		{
			objXMLHttp.readyState = 0;
		
			objXMLHttp.addEventListener("load", function ()
			{
			objXMLHttp.readyState = 4;
			
				if (typeof objXMLHttp.onreadystatechange == "function")
				{
				objXMLHttp.onreadystatechange();
				}
			}, false);
		}
	
		return objXMLHttp;
	},

	// 发送请求(方法[post,get], 地址, 数据, 回调函数)
	sendReq: function (method, url, data, callback)
	{
	var objXMLHttp = this._getInstance();
	
		with(objXMLHttp)
		{
			try
			{
			// 加随机数防止缓存
				if (url.indexOf("?") > 0)
				{
				url += "&randnum=" + Math.random();
				}
				else
				{
				url += "?randnum=" + Math.random();
				}
			
				open(method, url, true);
				
				// 设定请求编码方式，相当于iFrame中设定charSet
				setRequestHeader('Content-Type', 'application/x-www-form-urlencoded; charset=utf-8');
				setRequestHeader("Cache-Control","no-cache");
				send(data);
				onreadystatechange = function ()
				{
					if (objXMLHttp.readyState == 4 && (objXMLHttp.status == 200 || objXMLHttp.status == 304))
					{
					callback(objXMLHttp);
					}
				}
			}
			catch(e)
			{
			alert(e);
			}
		}
	}
};