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    1   package org.apache.turbine.util;
    2
    3   /*
    4    * Licensed to the Apache Software Foundation (ASF) under one
    5    * or more contributor license agreements.  See the NOTICE file
    6    * distributed with this work for additional information
    7    * regarding copyright ownership.  The ASF licenses this file
    8    * to you under the Apache License, Version 2.0 (the
    9    * "License"); you may not use this file except in compliance
    10   * with the License.  You may obtain a copy of the License at
    11   *
    12   *   http://www.apache.org/licenses/LICENSE-2.0
    13   *
    14   * Unless required by applicable law or agreed to in writing,
    15   * software distributed under the License is distributed on an
    16   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    17   * KIND, either express or implied.  See the License for the
    18   * specific language governing permissions and limitations
    19   * under the License.
    20   */
    21
    22  import java.text.SimpleDateFormat;
    23  import java.util.Date;
    24  import java.util.Locale;
    25  import java.util.TimeZone;
    26
    27  /**
    28   * This class provides utilities for handling some semi-trivial HTTP stuff that
    29   * would otherwise be handled elsewhere.
    30   *
    31   * @author <a href="mailto:magnus@handpoint.com">Magnús Þór Torfason</a>
    32   * @version $Id: HttpUtils.java 1071052 2011-02-15 20:54:47Z tv $
    33   */
    34  public class HttpUtils
    35  {
    36      /**
    37       * The date format to use for HTTP Dates.
    38       */
    39      private static SimpleDateFormat httpDateFormat;
    40
    41      static
    42      {
    43          httpDateFormat = new SimpleDateFormat(
    44                  "EEE, dd MMM yyyy HH:mm:ss z", Locale.US);
    45          httpDateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));
    46      }
    47
    48      /**
    49       * Formats a java Date according to rfc 1123, the rfc standard for dates in
    50       * http.
    51       *
    52       * @param date The Date to format
    53       * @return A String representation of the date
    54       */
    55      public static String formatHttpDate(Date date)
    56      {
    57          synchronized (httpDateFormat)
    58          {
    59              return httpDateFormat.format(date);
    60          }
    61      }
    62
    63      /**
    64       * This method sets the required expiration headers in the response for a
    65       * given RunData object.  This method attempts to set all relevant headers,
    66       * both for HTTP 1.0 and HTTP 1.1.
    67       *
    68       * @param data The RunData object we are setting cache information for.
    69       * @param expiry The number of milliseconds until the document should expire,
    70       * <code>0</code> indicating immediate expiration (i.e. no caching).
    71       */
    72      public static void setCacheHeaders(RunData data, int expiry)
    73      {
    74          if (0 == expiry)
    75          {
    76              data.getResponse().setHeader("Pragma", "no-cache");
    77              data.getResponse().setHeader("Cache-Control", "no-cache");
    78              data.getResponse().setDateHeader("Expires", System.currentTimeMillis());
    79          }
    80          else
    81          {
    82              data.getResponse().setDateHeader("Expires", System.currentTimeMillis() + expiry);
    83          }
    84      }
    85  }