将 HttpURLConnection 用于多部分数据

创建用于调用 multipart / form-data HttpURLConnection 请求的自定义类

MultipartUtility.java

public class MultipartUtility {
        private final String boundary;
        private static final String LINE_FEED = "\r\n";
        private HttpURLConnection httpConn;
        private String charset;
        private OutputStream outputStream;
        private PrintWriter writer;
    
        /**
         * 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)
                throws IOException {
            this.charset = charset;
    
            // creates a unique boundary based on time stamp
            boundary = "===" + System.currentTimeMillis() + "===";
            URL url = new URL(requestURL);
            httpConn = (HttpURLConnection) url.openConnection();
            httpConn.setUseCaches(false);
            httpConn.setDoOutput(true);    // indicates POST method
            httpConn.setDoInput(true);
            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;
            while ((bytesRead = inputStream.read(buffer)) != -1) {
                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 List<String> finish() throws IOException {
            List<String> response = new ArrayList<String>();
            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.add(line);
                }
                reader.close();
                httpConn.disconnect();
            } else {
                throw new IOException("Server returned non-OK status: " + status);
            }
            return response;
        }
    }

使用它（异步方式）

    MultipartUtility multipart = new MultipartUtility(requestURL, charset);

    // In your case you are not adding form data so ignore this
                /*This is to add parameter values */
                for (int i = 0; i < myFormDataArray.size(); i++) {
                    multipart.addFormField(myFormDataArray.get(i).getParamName(),
                            myFormDataArray.get(i).getParamValue());
                }

//add your file here.
                /*This is to add file content*/
                for (int i = 0; i < myFileArray.size(); i++) {
                    multipart.addFilePart(myFileArray.getParamName(),
                            new File(myFileArray.getFileName()));
                }

                List<String> response = multipart.finish();
                Debug.e(TAG, "SERVER REPLIED:");
                for (String line : response) {
                    Debug.e(TAG, "Upload Files Response:::" + line);
// get your server response here.
                    responseString = line;
                }