[R]AJAX中同时发送多个请求XMLHttpRequest对象处理
三月 7, 2007, Posted by cike at 4:36 下午
在ajax应用中，通常一个页面要同时发送多个请求，如果只有一个XMLHttpRequest对象，前面的请求还未完成，后面的就会把前面的覆盖掉，如果每次都创建一个新的XMLHttpRequest对象，也会造成浪费。解决的办法就是创建一个XMLHttpRequset的对象池，如果池里有空闲的对象，则使用此对象，否则将创建一个新的对象。
下面是我最近写的一个简单的类：
* XMLHttpRequest Object Pool
*
* @author legend <legendsky@hotmail.com>
* @link http://www.ugia.cn/?p=85
* @Copyright www.ugia.cn
*/
*
* @author legend <legendsky@hotmail.com>
* @link http://www.ugia.cn/?p=85
* @Copyright www.ugia.cn
*/
var XMLHttp = {
_objPool
_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
{
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
this._objPool[this._objPool.length] = this._createObj
();
return this._objPool[this._objPool.length - 1
];
},
},
_createObj: function ()
{
if (window.XMLHttpRequest)
{
var objXMLHttp = new XMLHttpRequest
{
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
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
if (objXMLHttp.readyState == null)
{
objXMLHttp.readyState = 0
;
objXMLHttp.addEventListener(“load”, function ()
{
objXMLHttp.readyState = 4
{
objXMLHttp.readyState = 4
;
if (typeof objXMLHttp.onreadystatechange == “function”)
{
objXMLHttp.onreadystatechange();
}
}, false
{
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
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
{
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
setRequestHeader(‘Content-Type’, ‘application/x-www-form-urlencoded; charset=UTF-8′);
send(data);
onreadystatechange = function ()
{
if (objXMLHttp.readyState == 4 && (objXMLHttp.status == 200 || objXMLHttp.status == 304))
{
callback(objXMLHttp);
}
}
}
catch(e)
{
alert(e);
}
}
}
};
setRequestHeader(‘Content-Type’, ‘application/x-www-form-urlencoded; charset=UTF-8′);
send(data);
onreadystatechange = function ()
{
if (objXMLHttp.readyState == 4 && (objXMLHttp.status == 200 || objXMLHttp.status == 304))
{
callback(objXMLHttp);
}
}
}
catch(e)
{
alert(e);
}
}
}
};
示例：
<script type=“text/javascript” src=“xmlhttp.js”></script>
<script type=”text/javascript”>
function test(obj)
{
alert(obj.statusText);
}demo 下载xmlhttp.js
<script type=”text/javascript”>
function test(obj)
{
alert(obj.statusText);
}demo 下载xmlhttp.js
XMLHttp.sendReq(‘GET’, ’http://www.ugia.cn/wp-data/test.htm’, ”, test);
XMLHttp.sendReq(‘GET’, ’http://www.ugia.cn/wp-data/test.htm’, ”, test);
XMLHttp.sendReq(‘GET’, ’http://www.ugia.cn/wp-data/test.htm’, ”, test);
XMLHttp.sendReq(‘GET’, ’http://www.ugia.cn/wp-data/test.htm’, ”, test);
alert(‘Pool length:’ + XMLHttp._objPool.length);
</script>
