Question

我正在编写一个Web服务，用于抓取并返回我们网站特定页面的HTML。该网站需要登录，所以我首先尝试将登录信息发布到登录页面，这样我就可以获得我需要的cookie来访问我想要的页面。然后，我试图抓住我真正想要的页面。

这是我的代码：

Dim http As HttpWebRequest = TryCast(WebRequest.Create("http://www.mywebsite.com/loginpage"), HttpWebRequest)
http.KeepAlive = True
http.Method = "POST"
http.ContentType = "application/x-www-form-urlencoded"
Dim postData As String = "My post data"
Dim dataBytes As Byte() = UTF8Encoding.UTF8.GetBytes(postData)
http.ContentLength = dataBytes.Length

Using postStream As Stream = http.GetRequestStream()
    postStream.Write(dataBytes, 0, dataBytes.Length)
End Using

Dim httpResponse As HttpWebResponse = TryCast(http.GetResponse(), HttpWebResponse)
http = TryCast(WebRequest.Create("http://www.mywebsite.com/desiredpage"), HttpWebRequest)
http.CookieContainer = New CookieContainer()
http.CookieContainer.Add(httpResponse.Cookies)
Dim httpResponse2 As HttpWebResponse = TryCast(http.GetResponse(), HttpWebResponse)

Using httpResponse2
    Using reader As New StreamReader(httpResponse2.GetResponseStream())
        Dim html As String = reader.ReadToEnd()
        Return html
    End Using
End Using

我的问题是：我只是收到登录页面的HTML，而不是成功登录并返回所需的cookie。这并不奇怪，因为如果cookie不存在，mywebsite.com/desiredpage会重定向到登录页面。

更新 Wireshark告诉我该网站正在返回6个Cookie：.ASPXANONYMOUS，language，USERNAME_CHANGED，authentication，.DOTNETNUKE和returnurl。我已经确认前3个存储在http.CookieContainer中，但其他3个不存储。

剩下的3发生了什么？

Answer 1

我的问题在于我将cookie从第一个请求传递到第二个请求。

创建单独的CookieContainer并在两个单独的请求中使用它解决了问题：

Dim http As HttpWebRequest = TryCast(WebRequest.Create("http://www.mywebsite.com/loginpage"), HttpWebRequest)
http.KeepAlive = True
http.Method = "POST"
http.ContentType = "application/x-www-form-urlencoded"
Dim postData As String = "My post data"
Dim dataBytes As Byte() = UTF8Encoding.UTF8.GetBytes(postData)
http.ContentLength = dataBytes.Length
Dim myCookies As CookieContainer = New CookieContainer()
http.CookieContainer = myCookies

Using postStream As Stream = http.GetRequestStream()
    postStream.Write(dataBytes, 0, dataBytes.Length)
End Using

Dim httpResponse As HttpWebResponse = TryCast(http.GetResponse(), HttpWebResponse)
Dim http2 As HttpWebRequest = TryCast(WebRequest.Create("http://www.mywebsite.com/desiredpage"), HttpWebRequest)
http2.CookieContainer = myCookies
Dim httpResponse2 As HttpWebResponse = TryCast(http2.GetResponse(), HttpWebResponse)

Using httpResponse2
    Using reader As New StreamReader(httpResponse2.GetResponseStream())
        Dim html As String = reader.ReadToEnd()
        Return html
    End Using
End Using

VB.NET - POST请求未正常运行

1 个答案: