annis.gui.servlets.ResourceServlet.java Source code

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Here is the source code for annis.gui.servlets.ResourceServlet.java

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/*
 * Copyright 2011 Corpuslinguistic working group Humboldt University Berlin
 *
 * 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 annis.gui.servlets;

import annis.libgui.visualizers.ResourcePlugin;
import java.io.*;
import java.net.URL;
import java.net.URLConnection;
import java.util.*;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import net.xeoh.plugins.base.Plugin;
import net.xeoh.plugins.base.annotations.PluginImplementation;
import net.xeoh.plugins.base.annotations.events.PluginLoaded;
import org.apache.commons.lang3.StringUtils;

/**
 * This servlet fetches resources for e.g. visualizers.
    
 * @author Thomas Krause <krause@informatik.hu-berlin.de>
 *
 */
@PluginImplementation
public class ResourceServlet extends HttpServlet implements Plugin {

    private static final long serialVersionUID = -8182635617256833563L;
    private static final Map<String, ResourcePlugin> resourceRegistry = Collections
            .synchronizedMap(new HashMap<String, ResourcePlugin>());

    @Override
    @SuppressWarnings("unchecked")
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        OutputStream outStream = response.getOutputStream();

        String completePath = request.getPathInfo();

        if (completePath == null) {
            response.sendError(404, "must provide a valid and existing path with a vistype");
            return;
        }

        // remove trailing /
        completePath = completePath.substring(1);

        String[] pathComponents = completePath.split("/");

        String vistype = pathComponents[0];

        if (pathComponents.length < 2) {
            response.sendError(404, "must provide a valid and existing path");
            return;
        }

        String path = StringUtils.join(Arrays.copyOfRange(pathComponents, 1, pathComponents.length), "/");

        // get the visualizer for this vistype
        ResourcePlugin vis = resourceRegistry.get(vistype);
        if (vis == null) {
            response.sendError(500, "There is no resource with the short name " + vistype);
        } else if (path.endsWith(".class")) {
            response.sendError(403, "illegal class path access");
        } else {
            URL resource = vis.getClass().getResource(path);
            if (resource == null) {
                response.sendError(404, path + " not found");
            } else {
                // check if it is new
                URLConnection resourceConnection = resource.openConnection();
                long resourceLastModified = resourceConnection.getLastModified();
                long requestLastModified = request.getDateHeader("If-Modified-Since");
                if (requestLastModified != -1 && resourceLastModified <= requestLastModified) {
                    response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
                } else {
                    response.addDateHeader("Last-Modified", resourceLastModified);
                    if ("localhost".equals(request.getServerName())) {
                        // does always expire right now
                        response.addDateHeader("Expires", new Date().getTime());
                    } else {
                        // expires in one minute per default
                        response.addDateHeader("Expires", new Date().getTime() + 60000);
                    }
                    // not in cache, stream out
                    String mimeType = getServletContext().getMimeType(path);
                    response.setContentType(mimeType);
                    if (mimeType.startsWith("text/")) {
                        response.setCharacterEncoding("UTF-8");
                    }
                    OutputStream bufferedOut = new BufferedOutputStream(outStream);
                    InputStream resourceInStream = new BufferedInputStream(resource.openStream());

                    try {
                        int v = -1;
                        while ((v = resourceInStream.read()) != -1) {
                            bufferedOut.write(v);
                        }
                    } finally {
                        resourceInStream.close();
                        bufferedOut.flush();
                        outStream.flush();
                    }
                }
            }
        }

    }

    @PluginLoaded
    public void newResourceAdded(ResourcePlugin vis) {
        resourceRegistry.put(vis.getShortName(), vis);
    }
}