MultipartHTTPUtility.java

gistfile1.java

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.List;

public class MultipartHTTPUtility {
        
        private final String        boundary;
        private static final String LINE_FEED = "\r\n";
        private HttpURLConnection   httpConnection;
        private String              charset   = "UTF-8";
        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 MultipartHTTPUtility(String requestURL) throws IOException {
                // creates a unique boundary based on time stamp
                boundary = "===" + System.currentTimeMillis() + "===";
                
                URL url = new URL(requestURL);
                httpConnection = (HttpURLConnection) url.openConnection();
                httpConnection.setUseCaches(false);
                httpConnection.setDoOutput(true); // indicates POST method
                httpConnection.setDoInput(true);
                
                httpConnection.setRequestMethod("POST");
                httpConnection.setRequestProperty("Connection", "Keep-Alive");
                httpConnection.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);
                
                httpConnection.setChunkedStreamingMode(1024);
                
                outputStream = httpConnection.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 = httpConnection.getResponseCode();
                if (status == HttpURLConnection.HTTP_OK) {
                        BufferedReader reader = new BufferedReader(new InputStreamReader(httpConnection.getInputStream()));
                        String line = null;
                        while ((line = reader.readLine()) != null) {
                                response.add(line);
                        }
                        reader.close();
                        httpConnection.disconnect();
                }
                else {
                        throw new IOException("Server returned non-OK status: " + status);
                }
                
                return response;
        }
        
}