在vb.net中调用REST：如何传递在cURL中工作的密钥“文件”

Question

我已经在这个问题上苦苦挣扎了差不多一个月了，我在网上找到了所有可以找到的东西，没有任何解决方案。 这是我的问题：我正在为RESTful API服务实现一个客户端，该服务必须通过POST调用在vb.net中发送XML文件。 我能够以xml格式获取一些数据，但是当发送这个Xml文件时，我总是得到“400错误的请求错误”。

我已经发现它必须是必须传递给服务器的密钥的问题（显然只接受POST的文件上传，我不能将其作为字符串发送）。

基本上这个调用与cURL一起使用，但我正在努力在vb.net中实现我自己的调用，传递正确的值。

工作cURL调用:(成功传输XML）

  c:>curl -u username:password -F "file=@filename.xml" -X POST http://hostname.com/URI?parameters

不工作的Vb.net代码:(这给了我400 Bad Request）

Dim ss As String = "" 'server says...
Dim S As String = txb_username.Text & ":" & txb_password.Text
Dim EncodedString As String = System.Convert.ToBase64String(System.Text.Encoding.UTF8.GetBytes(S))
Dim req As HttpWebRequest = Nothing
Dim res As HttpWebResponse = Nothing

Try
    Dim xmlDoc As System.Xml.XmlDocument = New System.Xml.XmlDocument
    xmlDoc.XmlResolver = Nothing

    xmlDoc.Load("c:\path\file4.xml")

    Dim sXML As String = "file" & xmlDoc.InnerXml '<- This is where I try to put the "KEY"

    Dim url As String = "http:/host.com+URI"

    req = CType(WebRequest.Create(url), Net.HttpWebRequest) 'or Directcast ... 
    req.Method = "POST"
    req.Headers.Add("Authorization: Basic " & EncodedString)
    req.ContentType = "multipart/form-data"
    req.ContentLength = sXML.Length 
    req.Accept = "*/*"

    System.Windows.Forms.Application.DoEvents()

    Dim sw As System.IO.StreamWriter = New System.IO.StreamWriter(req.GetRequestStream)
    StatusUpdate(sXML)
    sw.Write(sXML)
    sw.Close()
    ss = "server says: "
    res = CType(req.GetResponse, HttpWebResponse)
     StatusUpdate(req.ToString)
    Catch ex As Exception
        StatusUpdate(ss & ex.Message)
    Finally

End Try

是因为我想把它作为字符串发送吗？ （但是我怎么能把它作为一个文件发送？）为此我做了另一个发送数据字节的程序，但这个也给了我“400”，因为（我假设）我没有把“文件”键。

    Dim requestStream As Stream = Nothing
    Dim fileStream As FileStream = Nothing
    Dim uploadResponse As Net.HttpWebResponse = Nothing

    Try

        Dim uploadRequest As Net.HttpWebRequest = CType(Net.HttpWebRequest.Create(URI.Text & Uri_part2.text), Net.HttpWebRequest)

        uploadRequest.Method = Net.WebRequestMethods.Http.Post
        uploadRequest.ContentType = "text/xml; charset=utf-8"
        uploadRequest.Credentials = New NetworkCredential("user", "pass")
        uploadRequest.KeepAlive = True
        uploadRequest.UserAgent = "User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.0.10) Gecko/2009042316 Firefox/3.0.10"
        uploadRequest.Accept = ("text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8")
        uploadRequest.Headers.Add("Accept-Language: en-us,en;q=0.5")
        uploadRequest.Headers.Add("Accept-Encoding: gzip,deflate")
        uploadRequest.Headers.Add("Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7")
        uploadRequest.Headers.Add("Content-Disposition: form-data; name=""file"";")
        uploadRequest.ContentType = "application/xml; charset=utf-8"

        requestStream = uploadRequest.GetRequestStream()
        fileStream = File.Open("C:\example.xml", FileMode.Open)

        Dim a As Integer

        Dim buffer(1024) As Byte
        Dim bytesRead As Integer
        While True
            a = a + 1
            bytesRead = fileStream.Read(buffer, 0, buffer.Length)
            StatusUpdate(buffer(a))

            If bytesRead = 0 Then
                Exit While
            End If
            requestStream.Write(buffer, 0, bytesRead)

        End While

       requestStream.Close()

        uploadResponse = uploadRequest.GetResponse()
        Dim responseReader As StreamReader = New StreamReader(uploadRequest.GetResponse.GetResponseStream())
        Dim x As String = responseReader.ReadToEnd()
        responseReader.Close()
        StatusUpdate(x)


    Catch ex As UriFormatException
        StatusUpdate("UriFormatException: " & ex.Message)
    Catch ex As IOException
        StatusUpdate("IOException: " & ex.Message)
    Catch ex As Net.WebException
        StatusUpdate("Net.WebException: " & ex.Message)

    Finally

        If uploadResponse IsNot Nothing Then
            uploadResponse.Close()
        End If

        If fileStream IsNot Nothing Then
            fileStream.Close()
        End If

        If requestStream IsNot Nothing Then
            requestStream.Close()
        End If

    End Try

无论如何，我还尝试了其他2个客户端（POSTMAN和REST控制台，2个Google Chrome扩展程序），只有将值“file”添加到“key”字段中我才能使用它。 我必须插入特定的4个字符“文件”才能使其正常工作。 所以，问题是：如何在Vb.net调用中添加相同的值？ 如何在工作的Vb.net代码中翻译cURL调用的代码？ 非常感谢您的时间和帮助！

找到我想在这里添加的东西的图像，

PS我不能使用PUT，我必须使用POST（服务器限制）

我还添加了适用于我的目的的HTML代码，使用我的电脑上的服务器（再次参见“文件”键）

<html>
<body>
<form enctype="multipart/form-data" action="http://URI" method="POST">
<table border=0>

<tr>
<td align="right">File&nbsp;</td>
<td><input type="FILE" name="file"></td>
</tr>
<tr>
<td>&nbsp;</td>
<td><input type="submit"></td>
</tr>
</table>
</form>
</body>
</html>

此外，我还在PERL中粘贴了一个脚本，该脚本也可以在我的计算机上与服务器一起使用。

  #!perl

use strict;
use LWP; # Loads all important LWP classes

my $client_id         = 1234;
my $filename          = "new_file.xml";

### Prepare to make a request

my $browser = LWP::UserAgent->new;

my $url = "http://uri.com?&xx=$client_id";

my @post_pairs = (
    #'client_id_in' => $client_id,
    'file' => [$filename],
);

my @ns_headers = (
    'User-Agent' => 'Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.0.10) Gecko/2009042316 Firefox/3.0.10',
    'Accept' => 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
    'Accept-Language' => 'en-us,en;q=0.5',
    'Accept-Encoding' => 'gzip,deflate',
    'Accept-Charset' => 'ISO-8859-1,utf-8;q=0.7,*;q=0.7',
    'Authorization' => 'Basic base64EncodedCredentialsHere',
    'Content_Type' => 'form-data',
);

### Make a request
my $response = $browser->post($url, \@post_pairs, @ns_headers);
die "Can't get $url -- ", $response->status_line
        unless $response->is_success;

### Display the response
print STDOUT $response->content;

Answer 1

我认为你的问题是你真的不知道请求应该是什么样的，请使用fiddler来查看cURL发送的请求，并尝试使用vb.net实现相同的请求。 在我看来，你的secons代码段（使用缓冲区，而不是xml序列化程序）应该可以工作......但只有在服务器端可以理解这种结构。