裸寫http body服務報body Unexpected end of multipart data的解決辦法
拋出異常：
- 案例 調用騰訊OCR營業執照識別報錯。
調用騰訊OCR識別時簽名沒有問題，圖片base64也沒有問題，但是確收到對方服務報“內部錯誤”，經過聯系溝通，內部錯誤報：
“caught error Error: Unexpected end of multipart data”
抓包
通過抓包如下：
POST https://recognition.image.myqcloud.com/ocr/bizlicense HTTP/1.1
Content-Type: multipart/form-data; boundary=----------8d7055498b35e31
Authorization: yzo1HrKzdUF2rmYpiRoF482vvglhPTEyNTE3OTMwODAmYj10ZW5jZW50eXVuJms9QUtJRGExRDhtQmdBbEVWWWFSemp6emg5S0l6UWl2eTJDZUJUJmU9MTU2NTMzOTcxOSZ0PTE1NjI3NDc3MTkmcj0xOTA3MTAxNjM1JnU9MCZmPQ==
Host: recognition.image.myqcloud.com
Content-Length: 249
Expect: 100-continue
------------8d7055498b35e31
Content-Disposition: form-data; name="appid";
1251793080
------------8d7055498b35e31
Content-Disposition: form-data; name="image"; filename="yyzz.jpg"
Content-Type: image/jpeg
----------8d7055498b35e31--
解決問題
乍看上面抓包好像沒有什么問題，難道是Authorization加密出錯？圖片base64出錯？
其實真正出錯的的原因是Content-Type里面的橫線要比body里面的少兩個。body的最后一定要有兩個橫線結尾，並且body的橫線多少要一致（這個也是最重要的，不是有橫線就可以了）。
- 能正確運行的包應該如下：
POST https://recognition.image.myqcloud.com/ocr/bizlicense HTTP/1.1
Content-Type: multipart/form-data; boundary=----------8d7055498b35e31
Authorization: yzo1HrKzdUF2rmYpiRoF482vvglhPTEyNTE3OTMwODAmYj10ZW5jZW50eXVuJms9QUtJRGExRDhtQmdBbEVWWWFSemp6emg5S0l6UWl2eTJDZUJUJmU9MTU2NTMzOTcxOSZ0PTE1NjI3NDc3MTkmcj0xOTA3MTAxNjM1JnU9MCZmPQ==
Host: recognition.image.myqcloud.com
Content-Length: 249
Expect: 100-continue
------------8d7055498b35e31
Content-Disposition: form-data; name="appid";
1251793080
------------8d7055498b35e31
Content-Disposition: form-data; name="image"; filename="yyzz.jpg"
Content-Type: image/jpeg
------------8d7055498b35e31--
附C#調用騰訊OCR營業執照識別的部分源碼
static void IdentityBusinessLicense(string url)
{
HttpWebRequest webReq = (HttpWebRequest)WebRequest.Create(new Uri(url));
Stream memStream = new MemoryStream();
webReq.Method = "POST";
string boundary = "----------" + DateTime.Now.Ticks.ToString("x");// 邊界符
webReq.ContentType = "multipart/form-data; boundary=" + boundary;
//webReq.ContentType = "multipart/form-data;";
byte[] enter = Encoding.ASCII.GetBytes("\r\n"); //換行
memStream.Write(enter, 0, enter.Length);
Dictionary<string, string> dic = new Dictionary<string, string>()
{
{"appid",OCRConfig.appid}
};
//寫入文本字段
string inputPartHeaderFormat = "--" + boundary + "\r\n" + "Content-Disposition: form-data; name=\"{0}\";" + "\r\n\r\n{1}\r\n";
foreach (var kv in dic)
{
string inputPartHeader = string.Format(inputPartHeaderFormat, kv.Key, kv.Value);
var inputPartHeaderBytes = Encoding.ASCII.GetBytes(inputPartHeader);
memStream.Write(inputPartHeaderBytes, 0, inputPartHeaderBytes.Length);
}
var fileStream = new FileStream("yyzz.jpg", FileMode.Open, FileAccess.Read);
// 寫入文件
string imagePartHeader = "--" + boundary + "\r\n" +
"Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\n" +
"Content-Type: image/jpeg\r\n\r\n";
var header = string.Format(imagePartHeader, "image", "yyzz.jpg");
var headerbytes = Encoding.UTF8.GetBytes(header);
memStream.Write(headerbytes, 0, headerbytes.Length);
var buffer = new byte[1024];
int bytesRead;
while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
{
memStream.Write(buffer, 0, bytesRead);
}
// 最后的結束符
byte[] endBoundary = Encoding.ASCII.GetBytes("\r\n--" + boundary + "--\r\n");
memStream.Write(endBoundary, 0, endBoundary.Length);
// webReq.ContentLength = memStream.Length;
webReq.Headers.Add(HttpRequestHeader.Authorization, OCRApi.HmacSha1Sign());
webReq.Host = OCRConfig.Host;
var requestStream = webReq.GetRequestStream();
memStream.Position = 0;
memStream.CopyTo(requestStream);
HttpWebResponse response = (HttpWebResponse)webReq.GetResponse();
StreamReader sr = new StreamReader(response.GetResponseStream(), Encoding.UTF8);
var ret = sr.ReadToEnd();
sr.Close();
response.Close();
requestStream.Close();
memStream.Close();
}
總結
1、Content-Type: multipart/form-data; boundary=----------8d7055498b35e31 這里header的boundary橫線要比body的少兩個
2、------------8d7055498b35e31 body里面的橫線要比header的橫線要多兩個且所有body的橫線長度要一致，不是有橫線就可以了。
3、特別注意結尾處應該還有兩個“--”，注意是兩個橫線
4、還有一點就是要注意header之間，header與body之間，body與body之間的字段相隔多少個“\r\n”，這樣就可以了。