001    package org.apache.turbine.util;
002    
003    /*
004     * Licensed to the Apache Software Foundation (ASF) under one
005     * or more contributor license agreements.  See the NOTICE file
006     * distributed with this work for additional information
007     * regarding copyright ownership.  The ASF licenses this file
008     * to you under the Apache License, Version 2.0 (the
009     * "License"); you may not use this file except in compliance
010     * with the License.  You may obtain a copy of the License at
011     *
012     *   http://www.apache.org/licenses/LICENSE-2.0
013     *
014     * Unless required by applicable law or agreed to in writing,
015     * software distributed under the License is distributed on an
016     * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
017     * KIND, either express or implied.  See the License for the
018     * specific language governing permissions and limitations
019     * under the License.
020     */
021    
022    import java.text.SimpleDateFormat;
023    import java.util.Date;
024    import java.util.Locale;
025    import java.util.TimeZone;
026    
027    /**
028     * This class provides utilities for handling some semi-trivial HTTP stuff that
029     * would otherwise be handled elsewhere.
030     *
031     * @author <a href="mailto:magnus@handpoint.com">Magnús Þór Torfason</a>
032     * @version $Id: HttpUtils.java 1071052 2011-02-15 20:54:47Z tv $
033     */
034    public class HttpUtils
035    {
036        /**
037         * The date format to use for HTTP Dates.
038         */
039        private static SimpleDateFormat httpDateFormat;
040    
041        static
042        {
043            httpDateFormat = new SimpleDateFormat(
044                    "EEE, dd MMM yyyy HH:mm:ss z", Locale.US);
045            httpDateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));
046        }
047    
048        /**
049         * Formats a java Date according to rfc 1123, the rfc standard for dates in
050         * http.
051         *
052         * @param date The Date to format
053         * @return A String representation of the date
054         */
055        public static String formatHttpDate(Date date)
056        {
057            synchronized (httpDateFormat)
058            {
059                return httpDateFormat.format(date);
060            }
061        }
062    
063        /**
064         * This method sets the required expiration headers in the response for a
065         * given RunData object.  This method attempts to set all relevant headers,
066         * both for HTTP 1.0 and HTTP 1.1.
067         *
068         * @param data The RunData object we are setting cache information for.
069         * @param expiry The number of milliseconds until the document should expire,
070         * <code>0</code> indicating immediate expiration (i.e. no caching).
071         */
072        public static void setCacheHeaders(RunData data, int expiry)
073        {
074            if (0 == expiry)
075            {
076                data.getResponse().setHeader("Pragma", "no-cache");
077                data.getResponse().setHeader("Cache-Control", "no-cache");
078                data.getResponse().setDateHeader("Expires", System.currentTimeMillis());
079            }
080            else
081            {
082                data.getResponse().setDateHeader("Expires", System.currentTimeMillis() + expiry);
083            }
084        }
085    }