求Python Requests代码对应的VBA等效实现（获取重定向后URL）

原VBA代码的核心问题在于：

• 手动处理重定向时，每次都重复发送POST请求，但大多数3xx重定向（如302）会要求后续请求改用GET方法，而Python Requests会自动处理这种方法转换
• 未处理Location头中的相对URL（如果返回的是相对路径，直接赋值给url会导致无效请求）
• WinHTTP默认配置未正确匹配Requests的会话维护逻辑，比如自动携带Cookie

以下是与Python Requests行为一致的VBA代码，使用WinHTTP并正确处理重定向、方法转换和会话逻辑：

Sub GetFinalRedirectURL()
    Dim http As Object
    Dim currentUrl As String
    Dim postData As String
    
    ' 初始配置
    currentUrl = "https://moe-register.emis.gov.eg/account/authenticate"
    postData = "EmailAddress=471666845@minia4.moe.edu.eg"
    
    Set http = CreateObject("WinHTTP.WinHTTPRequest.5.1")
    ' 启用自动重定向，与Requests行为一致：302重定向自动将POST转为GET
    http.Option(6) = True
    http.Option(12) = True
    
    ' 发送初始POST请求
    http.Open "POST", currentUrl, False
    http.SetRequestHeader "Content-Type", "application/x-www-form-urlencoded"
    http.Send postData
    
    ' 获取最终重定向后的URL
    currentUrl = http.ResponseURL
    
    ' 输出结果
    MsgBox "Final URL After Redirection: " & currentUrl
    ' 可选：查看响应内容
    If Len(http.ResponseText) > 1024 Then
        MsgBox "Response Body (First 1024 chars): " & Left(http.ResponseText, 1024)
    Else
        MsgBox "Response Body: " & http.ResponseText
    End If
    
    Set http = Nothing
End Sub

• 自动重定向配置：通过http.Option(6)和http.Option(12)启用WinHTTP的自动重定向功能，它会自动处理3xx状态码，并且像Requests一样将302重定向的POST请求转为GET请求
• 最终URL获取：直接使用http.ResponseURL属性，该属性会返回经过所有重定向后的最终地址，无需手动解析Location头
• 会话维护：WinHTTP会自动维护请求过程中的Cookie，与Requests的会话行为一致，确保重定向请求携带必要的会话信息

如果需要自定义重定向逻辑，可使用以下手动处理版本：

Sub ManualRedirectHandling()
    Dim http As Object
    Dim currentUrl As String
    Dim postData As String
    Dim statusCode As Long
    Dim location As String
    Dim maxRedirects As Integer, redirectCount As Integer
    Dim isInitialPost As Boolean
    
    currentUrl = "https://moe-register.emis.gov.eg/account/authenticate"
    postData = "EmailAddress=471666845@minia4.moe.edu.eg"
    maxRedirects = 10
    redirectCount = 0
    isInitialPost = True
    
    Set http = CreateObject("WinHTTP.WinHTTPRequest.5.1")
    
    Do
        If isInitialPost Then
            ' 初始请求用POST
            http.Open "POST", currentUrl, False
            http.SetRequestHeader "Content-Type", "application/x-www-form-urlencoded"
            http.Send postData
            isInitialPost = False
        Else
            ' 重定向请求默认用GET
            http.Open "GET", currentUrl, False
            http.Send
        End If
        
        statusCode = http.Status
        
        If statusCode >= 300 And statusCode < 400 Then
            location = http.GetResponseHeader("Location")
            ' 处理相对URL
            If Left(location, 4) <> "http" Then
                If Left(location, 1) = "/" Then
                    location = Left(currentUrl, InStr(currentUrl, "//") + 1) & Split(currentUrl, "/")(2) & location
                Else
                    location = Left(currentUrl, InStrRev(currentUrl, "/")) & location
                End If
            End If
            currentUrl = location
            redirectCount = redirectCount + 1
        Else
            Exit Do
        End If
    Loop While redirectCount < maxRedirects
    
    MsgBox "Final URL After Redirection: " & currentUrl
    Set http = Nothing
End Sub

内容的提问来源于stack exchange，提问作者YasserKhalil