HTTP POST上傳文件說明及注意事項

這一陣子因為項目需要要對接別家公司的restful接口，其中有一個接口是上傳視頻文件。接着上網找找資料。后來文件是上傳成功了，但上服務器一看，文件沒有后綴，我勒個去，這是什么個鬼。接着繼續找資料，最終發現是因為在文件數據后面沒加上“\r\n”引起的，特發此博文備忘。在此感謝【小伊同學】的《c#代碼發送post請求，上傳文件》https://www.cnblogs.com/yinq/p/6045995.html和【imEgo】的《HTTP POST上傳文件格式說明》http://blog.sina.com.cn/s/blog_73b633110101jwxm.html。

public static Response FileLoadRequest(string url, string filePath, string rename = "")
{
    Response httpResponse = null;
    string fileName = FileHelper.GetFileName(filePath);
    string boundary = "ceshi";
    string Enter = "\r\n";

    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
    request.Method = "POST";
    request.ContentType = "multipart/form-data;charset=utf8;boundary=" + boundary;  //boundary這個屬性很重要
    //進行Session持久化
    request.CookieContainer = cookie;

    #region 將參數寫入請求流中
    Stream RequestStream = request.GetRequestStream();
    string fileContentStr = "--" + boundary + Enter
            + "Content-Type:application/octet-stream" + Enter
            + "Content-Disposition: form-data; name=\"file\"; filename=\"" + fileName + "\"" + Enter + Enter;
    var fileContentStrByte = Encoding.UTF8.GetBytes(fileContentStr);

    FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read);
    byte[] filedata = new byte[fs.Length];
    fs.Read(filedata, 0, Convert.ToInt32(fs.Length));
    fs.Close();

    RequestStream.Write(fileContentStrByte, 0, fileContentStrByte.Length);
    RequestStream.Write(filedata, 0, filedata.Length);

    //在文件數據末尾要加上“\r\n”
    string EndStr1 = Enter;
    var EndStr1Byte = Encoding.UTF8.GetBytes(EndStr1);
    RequestStream.Write(EndStr1Byte, 0, EndStr1Byte.Length);

    if (rename != "")
    {
        string fileNameStr = "--" + boundary + Enter
            + "Content-Disposition: form-data; name=\"file_name\"" + Enter + Enter
            + rename;
        var fileNameStrByte = Encoding.UTF8.GetBytes(fileNameStr);
        RequestStream.Write(fileNameStrByte, 0, fileNameStrByte.Length);
    }

    //在流末尾要加上--ceshi--的分隔符
    string EndStr = Enter + "--" + boundary + "--";
    var EndStrByte = Encoding.UTF8.GetBytes(EndStr);
    RequestStream.Write(EndStrByte, 0, EndStrByte.Length);
    #endregion

    string responseMessage = string.Empty;
    try
    {
        using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
        {

            StreamReader sr = new StreamReader(response.GetResponseStream(), Encoding.UTF8);
            responseMessage = sr.ReadToEnd();
            httpResponse = JsonConvert.DeserializeObject<Response>(responseMessage);
            response.Close();
        }
    }
    catch (WebException ex)
    {
        Program.log.Error(string.Format("System.Net.WebException:UrlGetRequest出錯,URL='{0}':", request.RequestUri), ex);
    }
    catch (Exception ex)
    {
        Program.log.Error(string.Format("UrlGetRequest出錯,URL='{0}':", request.RequestUri), ex);
    }

    return httpResponse;
}

下面引用下RFC的Sample：

Content-Type: multipart/form-data, boundary=AaB03x

--AaB03x
Content-Disposition: form-data; name="field1"

Joe Blow
--AaB03x
Content-Disposition: form-data; name="pics"; filename="file1.txt"
Content-Type: text/plain

 ... contents of file1.txt ...
--AaB03x--

首先，在Content-Type中，boundary這個屬性一定要加，但boundary屬性值隨意設置成什么都行，它不會出現在要上傳的數據里，只是起到分隔的作用。上面是設置成“Aab03x”。重點來了：每個參數之前需要加上“--boundary”，注意前面有“--”。參數最后結尾要加“--boundary--”。文件數據后要跟上“\r\n”(我就是因為沒加“\r\n，所以沒有文件后綴”)。在上傳文件的那一個參數的Content-Type：是根據上傳文件的后綴進行設置的，詳細對照表請參照：http://tool.oschina.net/commons/。如果不想根據文件后綴進行填充的話，可以直接用“application/octet-stream”。