500 HTTP POST 请求中的内部错误

我正在使用下面的代码通过HTTP POST上传文件，但我从服务器收到500内部服务器错误响应。

你能不能看一看，让我知道哪个代码部分是罪魁祸首/缺失。HTTPS连接中没有错误，我认为Header中存在一些问题，因此服务器不接受此请求。

    // Check server address
    url = new URL("https://example.com");
    String protocol = url.getProtocol(); 
    String host = url.getHost();
    String serviceRoot = url.getPath();

    // Build POST request
    HttpPost post = new HttpPost(new URI(protocol + "://" + host
            + serviceRoot));
    post.addHeader("User-Agent", "Test");
    post.addHeader("Content-type", "multipart/form-data"); 
    post.addHeader("Accept", "image/jpg"); 
    String authValue = "Basic "
            + Base64
                    .encodeBase64ToString(("username" + ":"
                            + "password").getBytes()) + " " + "realm=\"example.com\"";
    if (authValue != null) {
        post.addHeader("Authorization", authValue);
    }

    File file = new File("/sdcard/Download/IMAG0306.jpg");
    FileBody data = new FileBody(file);

    String file_type = "jpg" ;
    String description = "Test";

    MultipartEntity reqEntity = new MultipartEntity();
    reqEntity.addPart("file_name", new StringBody( file.getName() ) );
    reqEntity.addPart("description", new StringBody(description));
    reqEntity.addPart("file_type", new StringBody(file_type));
    reqEntity.addPart("data", data);

    post.setEntity(reqEntity); 

    if (true) {
        String trace = ">>> Send HTTP request:";
        trace += "\n " + post.getMethod() + " "
                + post.getRequestLine().getUri();
        System.out.println(trace);
    }

    if (true) {
        String trace = "<<< Send HTTP request-->:";
        trace += "\n" + post.toString();
        Header[] headers = post.getAllHeaders();
        for (Header header : headers) {
            trace += "\n" + header.getName() + " " + header.getValue();
        }
        System.out.println(trace);
    }

    HttpClient httpClient = createHttpClient();
    // replace with your url
    // “Authorization”, “Basic ” + encodedUsernamePassword);
    if (httpClient != null) {
        response = httpClient.execute(post);
        if (true) {
            String trace = "<<< Receive HTTP response:";
            trace += "\n" + response.getStatusLine().toString();
            Header[] headers = response.getAllHeaders();
            for (Header header : headers) {
                trace += "\n" + header.getName() + " " + header.getValue();
            }
            System.out.println(trace);
        }
    } else {
        throw new IOException("HTTP client not found");
    }

谢谢