AJAX（XMLHttpRequest）进行跨域请求方法详解（二）
2012-10-18 11:19
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注意：以下代码请在Firefox 3.5、Chrome 3.0、Safari 4之后的版本中进行测试。IE8的实现方法与其他浏览不同。
2，预检请求
预检请求首先需要向另外一个域名的资源发送一个 HTTP OPTIONS 请求头，其目的就是为了判断实际发送的请求是否是安全的。下面的2种情况需要进行预检：
a，不是上面的简单请求，比如使用Content-Type 为 application/xml 或 text/xml 的 POST 请求
b，在请求中设置自定义头，比如 X-JSON、X-MENGXIANHUI 等
注意：在 iis 里进行测试，必须在“应用程序扩展”里面配置 .aspx 扩展的动作允许 OPTIONS。
下面我们举一个预检的请求：
[xhtml]
view plaincopyprint?
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<htmlxmlns="http://www.w3.org/1999/xhtml">
<head>
<title>孟宪会之AJAX跨域请求测试</title>
</head>
<body>
<inputtype='button'value='开始测试'onclick='crossDomainRequest()'/>
<divid="content"></div>
<mce:scripttype="text/javascript"><!--
var xhr =new XMLHttpRequest();
var url ='http://dotnet.aspx.cc/PreflightedRequests.aspx';
function crossDomainRequest() {
document.getElementById("content").innerHTML ="开始进行请求……";
if (xhr) {
var xml ="<root>测试</root>";
xhr.open('POST', url, true);
xhr.setRequestHeader("POWERED-BY-MENGXIANHUI", "Approve");
xhr.setRequestHeader("Content-Type", "application/xml");
xhr.onreadystatechange =handler;
xhr.send(xml);
} else {
document.getElementById("content").innerHTML ="不能创建 XMLHttpRequest。";
}
}
function handler(evtXHR) {
if (xhr.readyState == 4) {
if (xhr.status == 200) {
var response =xhr.responseText;
document.getElementById("content").innerHTML ="结果：" + response;
} else {
document.getElementById("content").innerHTML ="不能进行跨越访问。";
}
}
else {
document.getElementById("content").innerHTML += "<br/>执行状态 readyState：" + xhr.readyState;
}
}
// --></mce:script>
</body>
</html>
点击“开始测试”按钮，将会执行下面的一系列请求。
[xhtml]
view plaincopyprint?
OPTIONS /PreflightedRequests.aspx HTTP/1.1
Host: dotnet.aspx.cc
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.2; zh-CN; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7 (.NET CLR 3.5.30729)
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: zh-cn,zh;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: GB2312,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Origin: http://www.meng_xian_hui.com:801 Access-Control-Request-Method: POST
Access-Control-Request-Headers: powered-by-mengxianhui
HTTP/1.x 200 OK
Date: Sun, 10 Jan 2010 14:00:34 GMT
Server: Microsoft-IIS/6.0
X-Powered-By: ASP.NET
X-AspNet-Version: 2.0.50727
Access-Control-Allow-Origin: http://www.meng_xian_hui.com:801 Access-Control-Allow-Methods: POST, GET, OPTIONS
Access-Control-Allow-Headers: POWERED-BY-MENGXIANHUI
Access-Control-Max-Age: 30
Set-Cookie: ASP.NET_SessionId=5npqri55dl1k1zvij1tlw3re;path=/;
HttpOnly
Cache-Control: private
Content-Length: 0
POST /PreflightedRequests.aspx HTTP/1.1
Host: dotnet.aspx.cc
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.2; zh-CN; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7 (.NET CLR 3.5.30729)
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: zh-cn,zh;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: GB2312,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
POWERED-BY-MENGXIANHUI: Approve
Content-Type: application/xml; charset=UTF-8
Referer: http://www.meng_xian_hui.com:801/CrossDomainAjax/PreflightedRequests.html Content-Length: 19
Origin: http://www.meng_xian_hui.com:801 Pragma: no-cache
Cache-Control: no-cache
<root>测试</root>
HTTP/1.x 200 OK
Date: Sun, 10 Jan 2010 14:00:34 GMT
Server: Microsoft-IIS/6.0
X-Powered-By: ASP.NET
X-AspNet-Version: 2.0.50727
Access-Control-Allow-Origin: http://www.meng_xian_hui.com:801 Set-Cookie: ASP.NET_SessionId=byvose45zmtbqy45d2a1jf2i;path=/;
HttpOnly
Cache-Control: private
Content-Type: text/html; charset=utf-8
Content-Length: 65
为什么会这样？细心的童鞋可能注意到了，在服务器端有一行代码 Response.AddHeader("Access-Control-Max-Age", "30"); 它是用来设置预检的有效时间的，单位是秒。这一点要特别注意。
2，预检请求
预检请求首先需要向另外一个域名的资源发送一个 HTTP OPTIONS 请求头，其目的就是为了判断实际发送的请求是否是安全的。下面的2种情况需要进行预检：
a，不是上面的简单请求，比如使用Content-Type 为 application/xml 或 text/xml 的 POST 请求
b，在请求中设置自定义头，比如 X-JSON、X-MENGXIANHUI 等
注意：在 iis 里进行测试，必须在“应用程序扩展”里面配置 .aspx 扩展的动作允许 OPTIONS。
下面我们举一个预检的请求：
[xhtml]
view plaincopyprint?
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<htmlxmlns="http://www.w3.org/1999/xhtml">
<head>
<title>孟宪会之AJAX跨域请求测试</title>
</head>
<body>
<inputtype='button'value='开始测试'onclick='crossDomainRequest()'/>
<divid="content"></div>
<mce:scripttype="text/javascript"><!--
var xhr =new XMLHttpRequest();
var url ='http://dotnet.aspx.cc/PreflightedRequests.aspx';
function crossDomainRequest() {
document.getElementById("content").innerHTML ="开始进行请求……";
if (xhr) {
var xml ="<root>测试</root>";
xhr.open('POST', url, true);
xhr.setRequestHeader("POWERED-BY-MENGXIANHUI", "Approve");
xhr.setRequestHeader("Content-Type", "application/xml");
xhr.onreadystatechange =handler;
xhr.send(xml);
} else {
document.getElementById("content").innerHTML ="不能创建 XMLHttpRequest。";
}
}
function handler(evtXHR) {
if (xhr.readyState == 4) {
if (xhr.status == 200) {
var response =xhr.responseText;
document.getElementById("content").innerHTML ="结果：" + response;
} else {
document.getElementById("content").innerHTML ="不能进行跨越访问。";
}
}
else {
document.getElementById("content").innerHTML += "<br/>执行状态 readyState：" + xhr.readyState;
}
}
// --></mce:script>
</body>
</html>
[xhtml] view plaincopyprint? <%@ PageLanguage="C#" %> <mce:scriptrunat="server"><!-- protected void Page_Load(object sender, EventArgs e) { if (Request.HttpMethod.Equals("GET")) { Response.Write("这个页面是用来测试跨域 POST 请求的，直接浏览意义不大。"); } else if (Request.HttpMethod.Equals("OPTIONS")) { //通知客户端允许预检请求。并设置缓存时间 Response.ClearContent(); Response.AddHeader("Access-Control-Allow-Origin", "http://www.meng_xian_hui.com:801"); Response.AddHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS"); Response.AddHeader("Access-Control-Allow-Headers", "POWERED-BY-MENGXIANHUI"); Response.AddHeader("Access-Control-Max-Age", "30"); //此过程无需返回数据 Response.End(); } else if (Request.HttpMethod.Equals("POST")) { if (Request.Headers["Origin"].Equals("http://www.meng_xian_hui.com:801")) { System.Xml.XmlDocument doc =new System.Xml.XmlDocument(); doc.Load(Request.InputStream); Response.AddHeader("Access-Control-Allow-Origin", "http://www.meng_xian_hui.com:801"); Response.Write("您提交的数据是：<br/><br/>" + Server.HtmlEncode(doc.OuterXml)); } else { Response.Write("不允许你的网站请求。"); } } } // --></mce:script> <%@ Page Language="C#" %> <mce:script runat="server"><!-- protected void Page_Load(object sender, EventArgs e) { if (Request.HttpMethod.Equals("GET")) { Response.Write("这个页面是用来测试跨域 POST 请求的，直接浏览意义不大。"); } else if (Request.HttpMethod.Equals("OPTIONS")) { //通知客户端允许预检请求。并设置缓存时间 Response.ClearContent(); Response.AddHeader("Access-Control-Allow-Origin", "http://www.meng_xian_hui.com:801"); Response.AddHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS"); Response.AddHeader("Access-Control-Allow-Headers", "POWERED-BY-MENGXIANHUI"); Response.AddHeader("Access-Control-Max-Age", "30"); //此过程无需返回数据 Response.End(); } else if (Request.HttpMethod.Equals("POST")) { if (Request.Headers["Origin"].Equals("http://www.meng_xian_hui.com:801")) { System.Xml.XmlDocument doc = new System.Xml.XmlDocument(); doc.Load(Request.InputStream); Response.AddHeader("Access-Control-Allow-Origin", "http://www.meng_xian_hui.com:801"); Response.Write("您提交的数据是：<br/><br/>" + Server.HtmlEncode(doc.OuterXml)); } else { Response.Write("不允许你的网站请求。"); } } } // --></mce:script>
点击“开始测试”按钮，将会执行下面的一系列请求。
[xhtml]
view plaincopyprint?
OPTIONS /PreflightedRequests.aspx HTTP/1.1
Host: dotnet.aspx.cc
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.2; zh-CN; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7 (.NET CLR 3.5.30729)
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: zh-cn,zh;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: GB2312,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Origin: http://www.meng_xian_hui.com:801 Access-Control-Request-Method: POST
Access-Control-Request-Headers: powered-by-mengxianhui
HTTP/1.x 200 OK
Date: Sun, 10 Jan 2010 14:00:34 GMT
Server: Microsoft-IIS/6.0
X-Powered-By: ASP.NET
X-AspNet-Version: 2.0.50727
Access-Control-Allow-Origin: http://www.meng_xian_hui.com:801 Access-Control-Allow-Methods: POST, GET, OPTIONS
Access-Control-Allow-Headers: POWERED-BY-MENGXIANHUI
Access-Control-Max-Age: 30
Set-Cookie: ASP.NET_SessionId=5npqri55dl1k1zvij1tlw3re;path=/;
HttpOnly
Cache-Control: private
Content-Length: 0
POST /PreflightedRequests.aspx HTTP/1.1
Host: dotnet.aspx.cc
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.2; zh-CN; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7 (.NET CLR 3.5.30729)
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: zh-cn,zh;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: GB2312,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
POWERED-BY-MENGXIANHUI: Approve
Content-Type: application/xml; charset=UTF-8
Referer: http://www.meng_xian_hui.com:801/CrossDomainAjax/PreflightedRequests.html Content-Length: 19
Origin: http://www.meng_xian_hui.com:801 Pragma: no-cache
Cache-Control: no-cache
<root>测试</root>
HTTP/1.x 200 OK
Date: Sun, 10 Jan 2010 14:00:34 GMT
Server: Microsoft-IIS/6.0
X-Powered-By: ASP.NET
X-AspNet-Version: 2.0.50727
Access-Control-Allow-Origin: http://www.meng_xian_hui.com:801 Set-Cookie: ASP.NET_SessionId=byvose45zmtbqy45d2a1jf2i;path=/;
HttpOnly
Cache-Control: private
Content-Type: text/html; charset=utf-8
Content-Length: 65
[xhtml] view plaincopyprint? POST /PreflightedRequests.aspx HTTP/1.1 Host: dotnet.aspx.cc User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.2; zh-CN; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7 (.NET CLR 3.5.30729) Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Language: zh-cn,zh;q=0.5 Accept-Encoding: gzip,deflate Accept-Charset: GB2312,utf-8;q=0.7,*;q=0.7 Keep-Alive: 300 Connection: keep-alive POWERED-BY-MENGXIANHUI: Approve Content-Type: application/xml; charset=UTF-8 Referer: http://www.meng_xian_hui.com:801/CrossDomainAjax/PreflightedRequests.html Content-Length: 19 Origin: http://www.meng_xian_hui.com:801 Pragma: no-cache Cache-Control: no-cache <root>测试</root> HTTP/1.x 200 OK Date: Sun, 10 Jan 2010 14:06:32 GMT Server: Microsoft-IIS/6.0 X-Powered-By: ASP.NET X-AspNet-Version: 2.0.50727 Access-Control-Allow-Origin: http://www.meng_xian_hui.com:801 Set-Cookie: ASP.NET_SessionId=qs1c4urxywdbdx55u04pvual;path=/; HttpOnly Cache-Control: private Content-Type: text/html; charset=utf-8 Content-Length: 65 POST /PreflightedRequests.aspx HTTP/1.1 Host: dotnet.aspx.cc User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.2; zh-CN; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7 (.NET CLR 3.5.30729) Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Language: zh-cn,zh;q=0.5 Accept-Encoding: gzip,deflate Accept-Charset: GB2312,utf-8;q=0.7,*;q=0.7 Keep-Alive: 300 Connection: keep-alive POWERED-BY-MENGXIANHUI: Approve Content-Type: application/xml; charset=UTF-8 Referer: http://www.meng_xian_hui.com:801/CrossDomainAjax/PreflightedRequests.html Content-Length: 19 Origin: http://www.meng_xian_hui.com:801 Pragma: no-cache Cache-Control: no-cache <root>测试</root> HTTP/1.x 200 OK Date: Sun, 10 Jan 2010 14:06:32 GMT Server: Microsoft-IIS/6.0 X-Powered-By: ASP.NET X-AspNet-Version: 2.0.50727 Access-Control-Allow-Origin: http://www.meng_xian_hui.com:801 Set-Cookie: ASP.NET_SessionId=qs1c4urxywdbdx55u04pvual; path=/; HttpOnly Cache-Control: private Content-Type: text/html; charset=utf-8 Content-Length: 65
为什么会这样？细心的童鞋可能注意到了，在服务器端有一行代码 Response.AddHeader("Access-Control-Max-Age", "30"); 它是用来设置预检的有效时间的，单位是秒。这一点要特别注意。
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