org.apache.myfaces.custom.skin.webapp.CachingStyleSheetLoader.java Source code

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Here is the source code for org.apache.myfaces.custom.skin.webapp.CachingStyleSheetLoader.java

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/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you 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 org.apache.myfaces.custom.skin.webapp;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.util.Calendar;

import javax.servlet.ServletConfig;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.myfaces.trinidadinternal.renderkit.core.xhtml.XhtmlConstants;

/**
 * This is an implementation of StyleSheetLoader that caches the stylesheet
 * into the web browser.
 */
public class CachingStyleSheetLoader implements StyleSheetLoader {
    private static final String STYLE_TYPE_TEXT_CSS = "text/css";
    private Log log = LogFactory.getLog(CachingStyleSheetLoader.class);

    /**
     * Loads the stylesheet only if the file has been modified or
     * the cache has expired.
     */
    public void loadStyleSheet(HttpServletRequest req, HttpServletResponse resp, ServletConfig config)
            throws IOException {
        File file = getFile(req, config);
        if (file != null && file.exists()) {
            if (isFileModified(file, req)) {
                long lastModified = file.lastModified();
                defineCaching(req, resp, lastModified);
                writeFile(file, resp);
            } else {
                resp.setStatus(HttpURLConnection.HTTP_NOT_MODIFIED);
                return;
            }
        } else {
            String requestURI = req.getRequestURI();
            String filename = requestURI.substring(requestURI.lastIndexOf("/") + 1);
            log.error("The resource " + filename + " was not found.");

            resp.setStatus(HttpURLConnection.HTTP_NOT_FOUND, filename);
            return;
        }
    }

    /**
     * Retrieves the stylesheet file from the server's temporary directory.
     * @param request
     * @param config
     * @return Returns the stylesheet file.
     */
    private File getFile(HttpServletRequest request, ServletConfig config) {
        String uri = request.getRequestURI();
        String filename = uri.substring(uri.lastIndexOf('/') + 1);

        File file = null;
        File tempDir = (File) config.getServletContext().getAttribute("javax.servlet.context.tempdir");
        if (tempDir != null && tempDir.exists()) {
            String absPath = tempDir.getAbsolutePath() + XhtmlConstants.STYLES_CACHE_DIRECTORY + filename;
            file = new File(absPath);
        }

        return file;
    }

    /**
     * Output http headers telling the browser (and possibly intermediate caches) how
     * to cache this data.
     * <p>
     * The expiry time in this header info is set to 7 days. This is not a problem as
     * the overall URI contains a "cache key" that changes whenever the webapp is
     * redeployed (see AddResource.getCacheKey), meaning that all browsers will
     * effectively reload files on webapp redeploy.
     */
    protected void defineCaching(HttpServletRequest request, HttpServletResponse response, long lastModified) {
        response.setDateHeader("Last-Modified", lastModified);

        Calendar expires = Calendar.getInstance();
        expires.add(Calendar.DAY_OF_YEAR, 7);
        response.setDateHeader("Expires", expires.getTimeInMillis());

        //12 hours: 43200 = 60s * 60 * 12
        response.setHeader("Cache-Control", "max-age=43200");
        response.setHeader("Pragma", "");
    }

    private boolean isFileModified(File file, HttpServletRequest request) {
        long lastModified = file.lastModified();
        long browserDate = request.getDateHeader("If-Modified-Since");

        // normalize to seconds - this should work with any os
        lastModified = (lastModified / 1000) * 1000;
        browserDate = (browserDate / 1000) * 1000;

        if (lastModified == browserDate) {
            return false;
        } else {
            return true;
        }
    }

    /**
     * Sends the file into the OutputStream of the response. 
     * @param file The stylesheet file.
     * @param response
     * @throws IOException
     */
    private void writeFile(File file, HttpServletResponse response) throws IOException {
        response.setContentType(STYLE_TYPE_TEXT_CSS);

        InputStream in = new FileInputStream(file);
        ServletOutputStream out = response.getOutputStream();

        byte[] buffer = new byte[1024];
        for (int size = in.read(buffer); size != -1; size = in.read(buffer)) {
            out.write(buffer, 0, size);
        }
        out.flush();
        in.close();
    }
}