Java tutorial
/* This file is part of Cyclos (www.cyclos.org). A project of the Social Trade Organisation (www.socialtrade.org). Cyclos is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. Cyclos is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with Cyclos; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ package nl.strohalm.cyclos.servlets; import java.io.File; import java.io.IOException; import java.util.HashMap; import java.util.Iterator; import java.util.Map; import java.util.Map.Entry; import javax.servlet.ServletConfig; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import nl.strohalm.cyclos.entities.customization.images.Image; import nl.strohalm.cyclos.entities.customization.images.Image.Nature; import nl.strohalm.cyclos.utils.ClassHelper; import nl.strohalm.cyclos.utils.ImageHelper.ImageType; import nl.strohalm.cyclos.utils.ResponseHelper; import nl.strohalm.cyclos.utils.SpringHelper; import nl.strohalm.cyclos.utils.WebImageHelper; import nl.strohalm.cyclos.utils.customizedfile.CustomizedFileHandler; import nl.strohalm.cyclos.utils.customizedfile.ImageChangeListener; import org.apache.commons.lang.StringUtils; /** * Servlet used to display system images * @author luis */ public class ImageByNameServlet extends HttpServlet { private static final long serialVersionUID = 8368765800788965163L; private ServletContext context; private Nature nature; private File imagePath; private File thumbnailPath; private final Map<String, String> resolvedNames = new HashMap<String, String>(); private WebImageHelper webImageHelper; private ResponseHelper responseHelper; @Override public synchronized void init(final ServletConfig config) throws ServletException { super.init(config); context = getServletContext(); webImageHelper = SpringHelper.bean(context, WebImageHelper.class); responseHelper = SpringHelper.bean(context, ResponseHelper.class); // Whenever the image is updated, we have to invalidate the cache SpringHelper.bean(context, CustomizedFileHandler.class).addImageChangeListener(new ImageChangeListener() { @Override public void onImageChanged(final Image image) { if (nature.equals(image.getNature())) { removeFromCache(image.getName()); } } }); final String natureParameter = config.getInitParameter("nature"); try { nature = Nature.valueOf(natureParameter); } catch (final Exception e) { context.log("Invalid nature for " + ClassHelper.getClassName(getClass()) + ": " + natureParameter); } imagePath = webImageHelper.imagePath(nature); thumbnailPath = webImageHelper.thumbnailPath(nature); } public void removeFromCache(final String name) { if (StringUtils.isEmpty(name)) { return; } synchronized (resolvedNames) { final Iterator<Map.Entry<String, String>> iterator = resolvedNames.entrySet().iterator(); while (iterator.hasNext()) { final Entry<String, String> entry = iterator.next(); final String current = entry.getKey(); if (name.equals(current) || name.startsWith(current + ".")) { iterator.remove(); } } } } @Override protected void doGet(final HttpServletRequest request, final HttpServletResponse response) throws ServletException, IOException { try { render(request, response); } catch (final Exception e) { return; } } /** * Render the image */ private void render(final HttpServletRequest request, final HttpServletResponse response) throws IOException { final File file = resolveFile(request); if (file == null) { response.sendError(HttpServletResponse.SC_NOT_FOUND); } else { ImageType type; try { type = ImageType.getByFileName(file.getName()); } catch (final Exception e) { type = null; } write(request, response, file, type); } } private File resolveFile(final boolean thumbnail, final String name) { if (name == null) { return null; } final File file = new File(thumbnail ? thumbnailPath : imagePath, name); if (!file.exists()) { throw new IllegalArgumentException("Invalid image file: " + file); } return file; } /** * Resolve the image file */ private File resolveFile(final HttpServletRequest request) { final boolean thumbnail = "true".equals(request.getParameter("thumbnail")); final String name = resolveName(request); return resolveFile(thumbnail, name); } /** * Resolve the image name, searching for an image with or without extension */ private String resolveName(final HttpServletRequest request) { final String name = request.getParameter("image"); if (StringUtils.isEmpty(name)) { return null; } synchronized (resolvedNames) { String resolved = resolvedNames.get(name); if (resolved == null) { final File path = webImageHelper.imagePath(nature); for (final String image : path.list()) { if (image.equals(name) || image.startsWith(name + ".")) { resolved = image; break; } } resolvedNames.put(name, resolved); } return resolved; } } /** * Write the image file to the response */ private void write(final HttpServletRequest request, final HttpServletResponse response, final File file, final ImageType type) throws IOException { final long ifModifiedSince = request.getDateHeader("If-Modified-Since"); if (ifModifiedSince > 0 && file.lastModified() <= ifModifiedSince) { // The contents have not changed response.setStatus(HttpServletResponse.SC_NOT_MODIFIED); return; } // The contents are modified, or not in browser's cache. Render it if (type != null) { response.setContentType(type.getContentType()); } responseHelper.writeFile(response, file); response.flushBuffer(); } }