協議錯誤|使用HttpClient或WebClient從API讀取JSON404

嘗試使用此服務獲取 JSON 資料以在本地進行進一步處理：

https://www.sec.gov/edgar/sec-api-documentation

測驗示例（來自上面的檔案鏈接）：

https://data.sec.gov/api/xbrl/frames/us-gaap/AccountsPayableCurrent/USD/CY2019Q1I.json

在瀏覽器中效果很好，但是我嘗試了幾種方法（如下所列）都失敗了，主要是協議錯誤 / 404

根據檔案 https://www.sec.gov/os/webmaster-faq#developers

我已經合并了所需的標題條目（我認為正確）

我一直讀到首選方法是使用 HttpClient，但是我遇到的所有簡單示例都是 C# 和/或使用我不理解的 lambda 運算式。我試圖盡可能地翻譯成 VB - 不確定我是否做對了。

我也在 App.config 中添加了這個：

<system.net>
  <settings>
    <httpWebRequest useUnsafeHeaderParsing = "true"/>
  </settings>
</system.net>

該應用程式是框架 4.7.2 上的 Win Forms 應用程式，作業系統是 Windows 10 Pro、20H2、64 位作業系統、基于 x64 的處理器

Imports System.IO
Imports System.Net
Imports System.Net.Http

Public Module SECJSON

    Public sourceUrl As String = "https://data.sec.gov/api/xbrl/frames/us-gaap/AccountsPayableCurrent/USD/CY2019Q1I.json"

    Public ua As String = "My Edgar Reader [email protected]"
    Public accept As String = ""
    'Public accept As String = "application/json"
    'Public accept As String = "text/plain"
    'Public accept As String = "*/*"

    Public Sub RunAttempts()
        Debug.WriteLine("HttpWebRequest:")
        Debug.WriteLine(Fetch1(sourceUrl))
        Debug.WriteLine("-----------")
        Debug.WriteLine("")

        Call Fetch2(sourceUrl)

        Debug.WriteLine("WebClient:")
        Debug.WriteLine(Fetch3(sourceUrl))
        Debug.WriteLine("-----------")
        Debug.WriteLine("")

        Debug.WriteLine("WebClient File:")
        Debug.WriteLine(Fetch4(sourceUrl))
        Debug.WriteLine("-----------")
        Debug.WriteLine("")

    End Sub

    Public Function Fetch1(url As String) As String
        Dim request As HttpWebRequest
        Dim response As HttpWebResponse
        Dim reader As StreamReader

        'request = WebRequest.Create(url)
        request = DirectCast(WebRequest.Create(url), HttpWebRequest)
        request.ContentType = "application/json"
        'request.Method = "POST"
        request.Method = "GET"

        request.UserAgent = ua
        request.Host = "www.sec.gov"
        request.Headers("Accept-Encoding") = "gzip, deflate"

        If Not (accept = "") Then request.Accept = accept

        Dim result As String = ""

        Try
            response = DirectCast(request.GetResponse(), HttpWebResponse)
            If response Is Nothing = False Then
                reader = New StreamReader(response.GetResponseStream())
                result = reader.ReadToEnd()
            Else
                result = "No Data"
            End If
        Catch ex As Exception
            result = ex.Message
        End Try

        Return result
    End Function

    Public Async Sub Fetch2(page As String)

        Dim request As New HttpRequestMessage(HttpMethod.Get, New Uri(page))
        If Not (accept = "") Then request.Headers.Accept.Add(New Headers.MediaTypeWithQualityHeaderValue(accept))
        request.Headers.TryAddWithoutValidation("User-Agent", ua)
        request.Headers.TryAddWithoutValidation("Host", "www.sec.gov")
        request.Headers.TryAddWithoutValidation("Accept-Encoding", "gzip, deflate")

        Dim client As HttpClient = New HttpClient

        Using response As HttpResponseMessage = Await client.SendAsync(request)
            Using content As HttpContent = response.Content
                'content.Headers.Remove("Content-Type")
                'content.Headers.Add("Content-Type", "application/json")
                Dim result As String = Await content.ReadAsStringAsync()
                If result Is Nothing Then
                    Debug.WriteLine("HttpClient:No result")
                Else
                    Debug.WriteLine("HttpClient:")
                    Debug.WriteLine(result)
                    Debug.WriteLine("-----------")
                    Debug.WriteLine("")
                End If
            End Using
        End Using
    End Sub

    Public Function Fetch3(url As String) As String

        Dim client As New WebClient()
        'ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12

        client.Headers.Add("User-Agent", ua)
        client.Headers.Add("Host", "www.sec.gov")
        client.Headers.Add("Accept-Encoding", "gzip, deflate")

        If Not (accept = "") Then client.Headers.Add("accept", accept)

        Dim ans As String = ""
        Try
            ans = client.DownloadString(New Uri(url))
        Catch ex As WebException
            If ex.Response Is Nothing = False Then
                'Dim dataStream As Stream = ex.Response.GetResponseStream
                'Dim reader As New StreamReader(dataStream)
                'ans = reader.ReadToEnd()
                ans = ex.Message & "|" & ex.Status.ToString
            Else
                ans = "No Response Stream"
            End If
        End Try

        Return ans
    End Function

    Public Function Fetch4(url As String) As String

        Dim client As New WebClient()
        Dim tmpFile As String = Path.Combine(Path.GetTempPath(), "edgar.txt")
        Debug.WriteLine(tmpFile)
        Try
            client.DownloadFile(New Uri(url), tmpFile)
            Return File.ReadAllText(tmpFile)
        Catch ex As WebException
            If ex.Response Is Nothing = False Then
                Return ex.Message & "|" & ex.Response.ContentType & " " & ex.Response.ContentLength.ToString
            Else
                Return ex.Message
            End If
        End Try

    End Function

End Module

uj5u.com熱心網友回復：

問題是您的主機標頭設定為“www.sec.gov”，因此請求將轉到“https://www.sec.gov/api/xbrl/frames/us-gaap/AccountsPayableCurrent/USD/CY2019Q1I.json” ' 而不是 'https://data.sec.gov/api/xbrl/frames/us-gaap/AccountsPayableCurrent/USD/CY2019Q1I.json'

解決方案很簡單，只需從以下位置編輯主機頭：

request.Host = "www.sec.gov"

到：

request.Host = "data.sec.gov"

下次如果您無法確定問題，請嘗試使用 Fiddler 查看您的請求有什么問題。

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