在 Android 中上传 Multipart 图像时出现服务器错误 415

Question

我在通过服务器上传图像文件时从服务器收到不支持的文件格式错误。

我关注了一个网址，并使用了他们的代码来让我感到舒服。

public class MultipartUtility {
    private final String boundary;
    private static final String LINE_FEED = "\r\n";
    private static final int CONNECTION_TIMEOUT = 5000; // 5 Seconds
    private HttpURLConnection httpConn;
    private String charset;
    private OutputStream outputStream;
    private PrintWriter writer;
    String authToken;

    /**
     * This constructor initializes a new HTTP POST request with content type
     * is set to multipart/form-data
     * @param requestURL
     * @param charset
     * @throws IOException
     */
    public MultipartUtility(String requestURL, String charset,  String authtoken)
            throws IOException {
        this.charset = charset;
        this.authToken = authtoken;

        // creates a unique boundary based on time stamp
        boundary = "===" + System.currentTimeMillis() + "===";

        URL url = new URL(requestURL);
        httpConn = (HttpURLConnection) url.openConnection();
        httpConn.setUseCaches(false);
        httpConn.setConnectTimeout(CONNECTION_TIMEOUT);
        httpConn.setDoOutput(true); // indicates POST method
        httpConn.setDoInput(true);
        httpConn.setRequestProperty("X-Auth-Token", authtoken);
        httpConn.setRequestProperty("Content-Type",
                "multipart/form-data; boundary=" + boundary);
        outputStream = httpConn.getOutputStream();
        writer = new PrintWriter(new OutputStreamWriter(outputStream, charset),
                true);
    }

    /**
     * Adds a form field to the request
     * @param name field name
     * @param value field value
     */
    public void addFormField(String name, String value) {
        writer.append("--" + boundary).append(LINE_FEED);
        writer.append("Content-Disposition: form-data; name=\"" + name + "\"")
                .append(LINE_FEED);
        writer.append("Content-Type: text/plain; charset=" + charset).append(
                LINE_FEED);
        writer.append(LINE_FEED);
        writer.append(value).append(LINE_FEED);
        writer.flush();
    }

    /**
     * Adds a upload file section to the request
     * @param fieldName name attribute in <input type="file" name="..." />
     * @param uploadFile a File to be uploaded
     * @throws IOException
     */
    public void addFilePart(String fieldName, File uploadFile)
            throws IOException {
        String fileName = uploadFile.getName();
        writer.append("--" + boundary).append(LINE_FEED);
        writer.append(
                "Content-Disposition: form-data; name=\"" + fieldName
                        + "\"; filename=\"" + fileName + "\"")
                .append(LINE_FEED);
        writer.append(
                "Content-Type: "
                        + URLConnection.guessContentTypeFromName(fileName))
                .append(LINE_FEED);
        writer.append("Content-Transfer-Encoding: binary").append(LINE_FEED);
        writer.append(LINE_FEED);
        writer.flush();

        FileInputStream inputStream = new FileInputStream(uploadFile);
        byte[] buffer = new byte[4096];
        int bytesRead = -1;
        long total = 0;
        while ((bytesRead = inputStream.read(buffer)) != -1) {
            /*if (listener != null) {
                total += bytesRead;
                //listener.onProgress((int) ((total * 100) / uploadFile.length()));
            }*/
            outputStream.write(buffer, 0, bytesRead);
        }
        outputStream.flush();
        inputStream.close();

        writer.append(LINE_FEED);
        writer.flush();
    }

    /**
     * Adds a header field to the request.
     * @param name - name of the header field
     * @param value - value of the header field
     */
    public void addHeaderField(String name, String value) {
        writer.append(name + ": " + value).append(LINE_FEED);
        writer.flush();
    }

    /**
     * Completes the request and receives response from the server.
     * @return a list of Strings as response in case the server returned
     * status OK, otherwise an exception is thrown.
     * @throws IOException
     */
    public String finish() throws IOException {
        StringBuilder response = null;

        writer.append(LINE_FEED).flush();
        writer.append("--" + boundary + "--").append(LINE_FEED);
        writer.close();

        // checks server's status code first
        int status = httpConn.getResponseCode();
        if (status == HttpURLConnection.HTTP_OK) {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    httpConn.getInputStream()));
            String line = null;
            while ((line = reader.readLine()) != null) {
                response.append(line);
            }
            reader.close();
            httpConn.disconnect();
        } else {
            throw new IOException("Server returned non-OK status: " + status + " " + httpConn.getErrorStream());
        }

        return response.toString();
    }
}

并使用 AsyncTask 中的此类..

MultipartUtility multipart = new MultipartUtility(url, charset, authToken);
            multipart.addFormField("guestId", params[1]);
            multipart.addFilePart("file", new File(params[0]));
            String response = multipart.finish(); // response from server.

我被困在这上面了，以至于我无法指出我自己的小错误..

请你帮我解决这个问题。

谢谢。

Answer 1

我认为“URLConnection.guessContentTypeFromName(fileName)”没有返回正确的内容类型。既然您提到您将图像作为文件发送，请尝试将“image/*”或“image/jpeg”（如果您知道图像类型）硬编码为 addFilePart() 方法中“Content-Type”标头字段的值。 希望对您有所帮助。