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无论使用任何语言做模拟登陆或者抓取访问页面，无外乎以下思路：
观察这三个请求的详细信息，不难看出第一个GET请求的地址可以由POST的响应得到，而第二个GET请求的地址又由第一个GET的响应得到。
HttpWebRequest request = null;
HttpWebResponse response = null;
string gethost = string.Empty;
CookieContainer cc = new CookieContainer();
string Cookiesstr = string.Empty;
try
{
//第一次POST请求
string postdata = "email=" + UserName.Replace("@", "%40") + "&password=" + PassWord + "&origURL=" + HostUrl + "&domain=renren.com";//模拟请求数据，数据样式可以用FireBug插件得到。人人网POST数据时，用户名邮箱中的“@”变为“%40”，所以我们也要作此变化
string LoginUrl="http://www.renren.com/PLogin.do";
request = (HttpWebRequest)WebRequest.Create(LoginUrl);//实例化web访问类
request.Method = "POST";//数据提交方式为POST
//模拟头
request.ContentType = "application/x-www-form-urlencoded";
byte[] postdatabytes = Encoding.UTF8.GetBytes(postdata);
request.ContentLength = postdatabytes.Length;
//request.Referer = "http://www.renren.com/Login.do?rf=r&domain=renren.com&origURL=" + HostUrl;
request.AllowAutoRedirect = false;
request.CookieContainer = cc;
request.KeepAlive = true;
//提交请求
Stream stream;
stream = request.GetRequestStream();
stream.Write(postdatabytes, 0, postdatabytes.Length);
stream.Close();
//接收响应
response = (HttpWebResponse)request.GetResponse();
//保存返回cookie
response.Cookies = request.CookieContainer.GetCookies(request.RequestUri);
CookieCollection cook = response.Cookies;
string strcrook = request.CookieContainer.GetCookieHeader(request.RequestUri);
Cookiesstr = strcrook;
//取第一次GET跳转地址
StreamReader sr = new StreamReader(response.GetResponseStream(), Encoding.UTF8);
string content = sr.ReadToEnd();
response.Close();
string[] substr = content.Split(new char[] { '"' });
gethost = substr[1];
}
catch (Exception)
{
//第一次POST出错；
}
注释写的很详细了，在这就不再分析，也许有人对request = (HttpWebRequest)WebRequest.Create(LoginUrl)有疑问，可以去google一下HttpWebRequest和WebRequest的区别，简单来说WebRequest是一个抽象类，不能直接实例化，需要被继承，而HttpWebRequest继承自WebRequest。 再模拟第一个和第二个GET请求
try
{
request = (HttpWebRequest)WebRequest.Create(gethost);
request.Method = "GET";
request.KeepAlive = true;
request.Headers.Add("Cookie:" + Cookiesstr);
request.CookieContainer = cc;
request.AllowAutoRedirect = false;
response = (HttpWebResponse)request.GetResponse();
//设置cookie
Cookiesstr = request.CookieContainer.GetCookieHeader(request.RequestUri);
//取再次跳转链接
StreamReader sr = new StreamReader(response.GetResponseStream(), Encoding.UTF8);
string ss = sr.ReadToEnd();
string[] substr = ss.Split(new char[] { '"' });
gethost = substr[1];
request.Abort();
sr.Close();
response.Close();
}
catch (Exception)
{
//第一次GET出错
}
try
{
//第二次GET请求
request = (HttpWebRequest)WebRequest.Create(gethost);
request.Method = "GET";
request.KeepAlive = true;
request.Headers.Add("Cookie:" + Cookiesstr);
request.CookieContainer = cc;
request.AllowAutoRedirect = false;
response = (HttpWebResponse)request.GetResponse();
//设置cookie
Cookiesstr = request.CookieContainer.GetCookieHeader(request.RequestUri);
request.Abort();
response.Close();
}
catch (Exception)
{
//第二次GET出错
}
GET与POST请求大同小异，这里便不再累述。三次请求结束，保存好你的cookie string，每次请求的时候都赋给请求的头部，你就处于登录状态了。 |
