如何解决使用REST WebService和VB.NET的附件
| 我目前正在使用VB.NET开发一个应用程序，其中正在使用REST WebServices。我已经能够使用REST进行基础操作，但是，我无法添加附件（更具体地说，是使用获得附件的REST上传文件）。我已经在网上进行了广泛的研究，但是到目前为止，我还无法在VB.NET中找到任何有效的示例。要实际上传数据，我使用System.Net.WebClient。以下VB.NET代码完成了重要工作：Dim Client As New System.Net.WebClient
Dim postBytes As Byte() = System.Text.Encoding.ASCII.GetBytes(postString)
Client.UploadData(URL,\"POST\",postBytes)
\"../REST/1.0/ticket/\" + ticketNumber + \"/comment?user=\" + userName + \"&pass=\" + password
postString = \"content=Text: RT Test\" + vbLf + \"Action: Comment\" + vbLf + \"Attachment: examplefile.jpg\" + vbLf + \"attachment_1=\"
解决方法
我们无法使用Client.UploadData（...），必须将整个帖子转换为字节，从附件之前的POST字段开始，然后是附件本身，最后是POST字段的其余部分。
Public Sub AddAttachmentToRT(ByVal url As String,ByVal fileName As String,ByVal filePath As String)
Dim dataBoundary As String = \"--xYzZY\"
Dim request As HttpWebRequest
Dim fileType As String = \"image/jpeg\" \'Will want to extract this to make it more generic from the uploaded file.
\'Create a POST web request to the REST interface using the passed URL
request = CType(WebRequest.Create(url),HttpWebRequest)
request.ContentType = \"multipart/form-data; boundary=xYzZY\"
request.Method = \"POST\"
request.KeepAlive = True
\'Write the request to the requestStream
Using requestStream As IO.Stream = request.GetRequestStream()
\'Create a variable \"attachment_1\" in the POST,specify the file name and file type
Dim preAttachment As String = dataBoundary + vbCrLf _
+ \"Content-Disposition: form-data; name=\"\"attachment_1\"\"; filename=\"\"\" + fileName + \"\"\"\" + vbCrLf _
+ \"Content-Type: \" + fileType + vbCrLf _
+ vbCrLf
\'Convert this preAttachment string to bytes
Dim preAttachmentBytes As Byte() = System.Text.Encoding.UTF8.GetBytes(preAttachment)
\'Write this preAttachment string to the stream
requestStream.Write(preAttachmentBytes,preAttachmentBytes.Length)
\'Write the file as bytes to the stream by passing its exact location
Using fileStream As New IO.FileStream(Server.MapPath(filePath + fileName),IO.FileMode.Open,IO.FileAccess.Read)
Dim buffer(4096) As Byte
Dim bytesRead As Int32 = fileStream.Read(buffer,buffer.Length)
Do While (bytesRead > 0)
requestStream.Write(buffer,bytesRead)
bytesRead = fileStream.Read(buffer,buffer.Length)
Loop
End Using
\'Create a variable named content in the POST,specify the attachment name and comment text
Dim postAttachment As String = vbCrLf _
+ dataBoundary + vbCrLf _
+ \"Content-Disposition: form-data; name=\"\"content\"\"\" + vbCrLf _
+ vbCrLf _
+ \"Action: comment\" + vbLf _
+ \"Attachment: \" + fileName + vbCrLf _
+ \"Text: Some description\" + vbCrLf _
+ vbCrLf _
+ \"--xYzZY--\"
\'Convert postAttachment string to bytes
Dim postAttachmentBytes As Byte() = System.Text.Encoding.UTF8.GetBytes(postAttachment)
\'Write the postAttachment string to the stream
requestStream.Write(postAttachmentBytes,postAttachmentBytes.Length)
End Using
Dim response As Net.WebResponse = Nothing
\'Get the response from our REST request to RT
\'Required to capture response,without this Try-Catch attaching will fail
Try
response = request.GetResponse()
Using responseStream As IO.Stream = response.GetResponseStream()
Using responseReader As New IO.StreamReader(responseStream)
Dim responseText = responseReader.ReadToEnd()
End Using
End Using
Catch exception As Net.WebException
response = exception.Response
If (response IsNot Nothing) Then
Using reader As New IO.StreamReader(response.GetResponseStream())
Dim responseText = reader.ReadToEnd()
End Using
response.Close()
End If
Finally
request = Nothing
End Try
End Sub
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