使用C#的HttpWebRequest模拟登陆访问人人网

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：
第一 启用一个web访问会话方法或者实例化一个web访问类，如.net中的HttpWebRequest；
第二 模拟POST或者GET方式提交的数据；
第三 模拟请求的头；
第四 提交请求并获得响应，及对响应做我们所需要的处理。
这里我们以人人网的登录为例，将涉及到POST以及GET两种请求方式。
在之前的文章《免费网页抓包工具，火狐插件FireBug的抓包使用教程》中我们知道，登陆人人网的时候，一共做了一个POST请求以及两个GET请求，如下图：

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。
先来模拟第一个POST请求

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；
}

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
}

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。
人人网的HttpWebRequest登陆模拟很简单，但是POST及GET涉及到了，是个不错的案例。
当然，在.net想做自动访问的操作还可以使用WebBrowser控件，而且还能够和HttpWebRequest共用cookie，抛砖引玉一下不在本篇文章的讨论范围。