Java tutorial
/* * Copyright 2008 ZXing authors * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.google.zxing.web; import com.google.zxing.BarcodeFormat; import com.google.zxing.BinaryBitmap; import com.google.zxing.ChecksumException; import com.google.zxing.DecodeHintType; import com.google.zxing.FormatException; import com.google.zxing.LuminanceSource; import com.google.zxing.MultiFormatReader; import com.google.zxing.NotFoundException; import com.google.zxing.Reader; import com.google.zxing.ReaderException; import com.google.zxing.Result; import com.google.zxing.client.j2se.BufferedImageLuminanceSource; import com.google.zxing.client.j2se.ImageReader; import com.google.zxing.common.GlobalHistogramBinarizer; import com.google.zxing.common.HybridBinarizer; import com.google.zxing.multi.GenericMultipleBarcodeReader; import com.google.zxing.multi.MultipleBarcodeReader; import com.google.common.io.Resources; import com.google.common.net.HttpHeaders; import com.google.common.net.MediaType; import java.awt.color.CMMException; import java.awt.image.BufferedImage; import java.io.IOException; import java.io.InputStream; import java.io.OutputStreamWriter; import java.io.Writer; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URI; import java.net.URISyntaxException; import java.net.URL; import java.nio.charset.StandardCharsets; import java.util.ArrayList; import java.util.Arrays; import java.util.Collection; import java.util.Collections; import java.util.EnumMap; import java.util.EnumSet; import java.util.Locale; import java.util.Map; import java.util.ResourceBundle; import java.util.logging.Level; import java.util.logging.Logger; import javax.imageio.ImageIO; import javax.servlet.ServletConfig; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.annotation.MultipartConfig; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.Part; /** * {@link HttpServlet} which decodes images containing barcodes. Given a URL, it will * retrieve the image and decode it. It can also process image files uploaded via POST. * * @author Sean Owen */ @MultipartConfig(maxFileSize = 10_000_000, maxRequestSize = 10_000_000, fileSizeThreshold = 1_000_000, location = "/tmp") @WebServlet(value = "/w/decode", loadOnStartup = 1) public final class DecodeServlet extends HttpServlet { private static final Logger log = Logger.getLogger(DecodeServlet.class.getName()); // No real reason to let people upload more than a 10MB image private static final long MAX_IMAGE_SIZE = 10_000_000L; // No real reason to deal with more than maybe 10 megapixels private static final int MAX_PIXELS = 10_000_000; private static final byte[] REMAINDER_BUFFER = new byte[32768]; private static final Map<DecodeHintType, Object> HINTS; private static final Map<DecodeHintType, Object> HINTS_PURE; static { HINTS = new EnumMap<>(DecodeHintType.class); HINTS.put(DecodeHintType.TRY_HARDER, Boolean.TRUE); HINTS.put(DecodeHintType.POSSIBLE_FORMATS, EnumSet.allOf(BarcodeFormat.class)); HINTS_PURE = new EnumMap<>(HINTS); HINTS_PURE.put(DecodeHintType.PURE_BARCODE, Boolean.TRUE); } private Iterable<String> blockedURLSubstrings; @Override public void init(ServletConfig servletConfig) throws ServletException { Logger logger = Logger.getLogger("com.google.zxing"); ServletContext context = servletConfig.getServletContext(); logger.addHandler(new ServletContextLogHandler(context)); URL blockURL = context.getClassLoader().getResource("/private/uri-block-substrings.txt"); if (blockURL == null) { blockedURLSubstrings = Collections.emptyList(); } else { try { blockedURLSubstrings = Resources.readLines(blockURL, StandardCharsets.UTF_8); } catch (IOException ioe) { throw new ServletException(ioe); } log.info("Blocking URIs containing: " + blockedURLSubstrings); } } @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String imageURIString = request.getParameter("u"); if (imageURIString == null || imageURIString.isEmpty()) { log.info("URI was empty"); errorResponse(request, response, "badurl"); return; } imageURIString = imageURIString.trim(); for (CharSequence substring : blockedURLSubstrings) { if (imageURIString.contains(substring)) { log.info("Disallowed URI " + imageURIString); errorResponse(request, response, "badurl"); return; } } URI imageURI; try { imageURI = new URI(imageURIString); // Assume http: if not specified if (imageURI.getScheme() == null) { imageURI = new URI("http://" + imageURIString); } } catch (URISyntaxException urise) { log.info("URI " + imageURIString + " was not valid: " + urise); errorResponse(request, response, "badurl"); return; } // Shortcut for data URI if ("data".equals(imageURI.getScheme())) { try { BufferedImage image = ImageReader.readDataURIImage(imageURI); processImage(image, request, response); } catch (IOException ioe) { log.info(ioe.toString()); errorResponse(request, response, "badurl"); } return; } URL imageURL; try { imageURL = imageURI.toURL(); } catch (MalformedURLException ignored) { log.info("URI was not valid: " + imageURIString); errorResponse(request, response, "badurl"); return; } String protocol = imageURL.getProtocol(); if (!"http".equalsIgnoreCase(protocol) && !"https".equalsIgnoreCase(protocol)) { log.info("URI was not valid: " + imageURIString); errorResponse(request, response, "badurl"); return; } HttpURLConnection connection; try { connection = (HttpURLConnection) imageURL.openConnection(); } catch (IllegalArgumentException ignored) { log.info("URI could not be opened: " + imageURL); errorResponse(request, response, "badurl"); return; } connection.setAllowUserInteraction(false); connection.setReadTimeout(5000); connection.setConnectTimeout(5000); connection.setRequestProperty(HttpHeaders.USER_AGENT, "zxing.org"); connection.setRequestProperty(HttpHeaders.CONNECTION, "close"); try { connection.connect(); } catch (IOException | IllegalArgumentException e) { // Encompasses lots of stuff, including // java.net.SocketException, java.net.UnknownHostException, // javax.net.ssl.SSLPeerUnverifiedException, // org.apache.http.NoHttpResponseException, // org.apache.http.client.ClientProtocolException, log.info(e.toString()); errorResponse(request, response, "badurl"); return; } try (InputStream is = connection.getInputStream()) { try { if (connection.getResponseCode() != HttpServletResponse.SC_OK) { log.info("Unsuccessful return code: " + connection.getResponseCode()); errorResponse(request, response, "badurl"); return; } if (connection.getHeaderFieldInt(HttpHeaders.CONTENT_LENGTH, 0) > MAX_IMAGE_SIZE) { log.info("Too large"); errorResponse(request, response, "badimage"); return; } log.info("Decoding " + imageURL); processStream(is, request, response); } finally { consumeRemainder(is); } } catch (IOException ioe) { log.info(ioe.toString()); errorResponse(request, response, "badurl"); } finally { connection.disconnect(); } } private static void consumeRemainder(InputStream is) { try { int available; while ((available = is.available()) > 0) { is.read(REMAINDER_BUFFER, 0, available); // don't care about value, or collision } } catch (IOException | IndexOutOfBoundsException ioe) { // sun.net.www.http.ChunkedInputStream.read is throwing IndexOutOfBoundsException // continue } } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { Collection<Part> parts; try { parts = request.getParts(); } catch (IllegalStateException ise) { log.info("File upload was too large or invalid"); errorResponse(request, response, "badimage"); return; } catch (IOException ioe) { log.info(ioe.toString()); errorResponse(request, response, "badurl"); return; } Part fileUploadPart = null; for (Part part : parts) { if (part.getHeader(HttpHeaders.CONTENT_DISPOSITION) != null) { fileUploadPart = part; break; } } if (fileUploadPart == null) { log.info("File upload was not multipart"); errorResponse(request, response, "badimage"); } else { log.info("Decoding uploaded file"); try (InputStream is = fileUploadPart.getInputStream()) { processStream(is, request, response); } } } private static void processStream(InputStream is, HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { BufferedImage image; try { image = ImageIO.read(is); } catch (IOException | CMMException | IllegalArgumentException ioe) { log.info(ioe.toString()); // Have seen these in some logs errorResponse(request, response, "badimage"); return; } if (image == null) { errorResponse(request, response, "badimage"); return; } if (image.getHeight() <= 1 || image.getWidth() <= 1 || image.getHeight() * image.getWidth() > MAX_PIXELS) { log.info("Dimensions out of bounds: " + image.getWidth() + 'x' + image.getHeight()); errorResponse(request, response, "badimage"); return; } processImage(image, request, response); } private static void processImage(BufferedImage image, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { LuminanceSource source = new BufferedImageLuminanceSource(image); BinaryBitmap bitmap = new BinaryBitmap(new GlobalHistogramBinarizer(source)); Collection<Result> results = new ArrayList<>(1); try { Reader reader = new MultiFormatReader(); ReaderException savedException = null; try { // Look for multiple barcodes MultipleBarcodeReader multiReader = new GenericMultipleBarcodeReader(reader); Result[] theResults = multiReader.decodeMultiple(bitmap, HINTS); if (theResults != null) { results.addAll(Arrays.asList(theResults)); } } catch (ReaderException re) { savedException = re; } if (results.isEmpty()) { try { // Look for pure barcode Result theResult = reader.decode(bitmap, HINTS_PURE); if (theResult != null) { results.add(theResult); } } catch (ReaderException re) { savedException = re; } } if (results.isEmpty()) { try { // Look for normal barcode in photo Result theResult = reader.decode(bitmap, HINTS); if (theResult != null) { results.add(theResult); } } catch (ReaderException re) { savedException = re; } } if (results.isEmpty()) { try { // Try again with other binarizer BinaryBitmap hybridBitmap = new BinaryBitmap(new HybridBinarizer(source)); Result theResult = reader.decode(hybridBitmap, HINTS); if (theResult != null) { results.add(theResult); } } catch (ReaderException re) { savedException = re; } } if (results.isEmpty()) { try { throw savedException == null ? NotFoundException.getNotFoundInstance() : savedException; } catch (FormatException | ChecksumException e) { log.info(e.getMessage()); errorResponse(request, response, "format"); } catch (ReaderException e) { // Including NotFoundException log.info(e.getMessage()); errorResponse(request, response, "notfound"); } return; } } catch (RuntimeException re) { // Call out unexpected errors in the log clearly log.log(Level.WARNING, "Unexpected exception from library", re); throw new ServletException(re); } String fullParameter = request.getParameter("full"); boolean minimalOutput = fullParameter != null && !Boolean.parseBoolean(fullParameter); if (minimalOutput) { response.setContentType(MediaType.PLAIN_TEXT_UTF_8.toString()); response.setCharacterEncoding(StandardCharsets.UTF_8.name()); try (Writer out = new OutputStreamWriter(response.getOutputStream(), StandardCharsets.UTF_8)) { for (Result result : results) { out.write(result.getText()); out.write('\n'); } } } else { request.setAttribute("results", results); request.getRequestDispatcher("decoderesult.jspx").forward(request, response); } } private static void errorResponse(HttpServletRequest request, HttpServletResponse response, String key) throws ServletException, IOException { Locale locale = request.getLocale(); if (locale == null) { locale = Locale.ENGLISH; } ResourceBundle bundle = ResourceBundle.getBundle("Strings", locale); String title = bundle.getString("response.error." + key + ".title"); String text = bundle.getString("response.error." + key + ".text"); request.setAttribute("title", title); request.setAttribute("text", text); request.getRequestDispatcher("response.jspx").forward(request, response); } }