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1   /*
2    * $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//httpclient/src/java/org/apache/commons/httpclient/util/DateUtil.java,v 1.2 2004/12/24 20:36:13 olegk Exp $
3    * $Revision: 155418 $
4    * $Date: 2005-02-26 08:01:52 -0500 (Sat, 26 Feb 2005) $
5    *
6    * ====================================================================
7    *
8    *  Copyright 1999-2004 The Apache Software Foundation
9    *
10   *  Licensed under the Apache License, Version 2.0 (the "License");
11   *  you may not use this file except in compliance with the License.
12   *  You may obtain a copy of the License at
13   *
14   *      http://www.apache.org/licenses/LICENSE-2.0
15   *
16   *  Unless required by applicable law or agreed to in writing, software
17   *  distributed under the License is distributed on an "AS IS" BASIS,
18   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
19   *  See the License for the specific language governing permissions and
20   *  limitations under the License.
21   * ====================================================================
22   *
23   * This software consists of voluntary contributions made by many
24   * individuals on behalf of the Apache Software Foundation.  For more
25   * information on the Apache Software Foundation, please see
26   * <http://www.apache.org/>.
27   *
28   */
29  
30  package org.apache.commons.httpclient.util;
31  
32  import java.text.ParseException;
33  import java.text.SimpleDateFormat;
34  import java.util.Arrays;
35  import java.util.Calendar;
36  import java.util.Collection;
37  import java.util.Date;
38  import java.util.Iterator;
39  import java.util.Locale;
40  import java.util.TimeZone;
41  
42  import org.apache.commons.logging.Log;
43  import org.apache.commons.logging.LogFactory;
44  
45  /***
46   * A utility class for parsing and formatting HTTP dates as used in cookies and 
47   * other headers.  This class handles dates as defined by RFC 2616 section 
48   * 3.3.1 as well as some other common non-standard formats.
49   * 
50   * @author Christopher Brown
51   * @author Michael Becke
52   */
53  public class DateUtil {
54  
55      /*** Log object for this class. */
56      private static final Log LOG = LogFactory.getLog(DateUtil.class);
57  
58      /***
59       * Date format pattern used to parse HTTP date headers in RFC 1123 format.
60       */
61      public static final String PATTERN_RFC1123 = "EEE, dd MMM yyyy HH:mm:ss zzz";
62  
63      /***
64       * Date format pattern used to parse HTTP date headers in RFC 1036 format.
65       */
66      public static final String PATTERN_RFC1036 = "EEEE, dd-MMM-yy HH:mm:ss zzz";
67  
68      /***
69       * Date format pattern used to parse HTTP date headers in ANSI C 
70       * <code>asctime()</code> format.
71       */
72      public static final String PATTERN_ASCTIME = "EEE MMM d HH:mm:ss yyyy";
73  
74      private static final Collection DEFAULT_PATTERNS = Arrays.asList(
75      		new String[] { PATTERN_ASCTIME, PATTERN_RFC1036, PATTERN_RFC1123 } );
76      
77      private static final Date DEFAULT_TWO_DIGIT_YEAR_START;
78      
79      static {
80          Calendar calendar = Calendar.getInstance();
81          calendar.set(2000, Calendar.JANUARY, 1, 0, 0);
82          DEFAULT_TWO_DIGIT_YEAR_START = calendar.getTime(); 
83      }
84      
85      /***
86       * Parses a date value.  The formats used for parsing the date value are retrieved from
87       * the default http params.
88       *
89       * @param dateValue the date value to parse
90       * 
91       * @return the parsed date
92       *
93       * @throws DateParseException if the value could not be parsed using any of the 
94       * supported date formats
95       */
96      public static Date parseDate(String dateValue) throws DateParseException {
97          return parseDate(dateValue, null, null);
98      }
99      
100     /***
101      * Parses the date value using the given date formats.
102      * 
103      * @param dateValue the date value to parse
104      * @param dateFormats the date formats to use
105      * 
106      * @return the parsed date
107      * 
108      * @throws DateParseException if none of the dataFormats could parse the dateValue
109      */
110     public static Date parseDate(String dateValue, Collection dateFormats) 
111         throws DateParseException {
112         return parseDate(dateValue, dateFormats, null);
113     }
114     
115     /***
116      * Parses the date value using the given date formats.
117      * 
118      * @param dateValue the date value to parse
119      * @param dateFormats the date formats to use
120      * @param startDate During parsing, two digit years will be placed in the range 
121      * <code>startDate</code> to <code>startDate + 100 years</code>. This value may 
122      * be <code>null</code>. When <code>null</code> is given as a parameter, year 
123      * <code>2000</code> will be used. 
124      * 
125      * @return the parsed date
126      * 
127      * @throws DateParseException if none of the dataFormats could parse the dateValue
128      */
129     public static Date parseDate(
130         String dateValue, 
131         Collection dateFormats,
132         Date startDate 
133     ) throws DateParseException {
134         
135         if (dateValue == null) {
136             throw new IllegalArgumentException("dateValue is null");
137         }
138         if (dateFormats == null) {
139         	dateFormats = DEFAULT_PATTERNS;
140         }
141         if (startDate == null) {
142             startDate = DEFAULT_TWO_DIGIT_YEAR_START;
143         }
144         // trim single quotes around date if present
145         // see issue #5279
146         if (dateValue.length() > 1 
147             && dateValue.startsWith("'") 
148             && dateValue.endsWith("'")
149         ) {
150             dateValue = dateValue.substring (1, dateValue.length() - 1);
151         }
152         
153         SimpleDateFormat dateParser = null;        
154         Iterator formatIter = dateFormats.iterator();
155         
156         while (formatIter.hasNext()) {
157             String format = (String) formatIter.next();            
158             if (dateParser == null) {
159                 dateParser = new SimpleDateFormat(format, Locale.US);
160                 dateParser.setTimeZone(TimeZone.getTimeZone("GMT"));
161                 dateParser.set2DigitYearStart(startDate);
162             } else {
163                 dateParser.applyPattern(format);                    
164             }
165             try {
166                 return dateParser.parse(dateValue);
167             } catch (ParseException pe) {
168                 // ignore this exception, we will try the next format
169             }                
170         }
171         
172         // we were unable to parse the date
173         throw new DateParseException("Unable to parse the date " + dateValue);        
174     }
175 
176     /***
177      * Formats the given date according to the RFC 1123 pattern.
178      * 
179      * @param date The date to format.
180      * @return An RFC 1123 formatted date string.
181      * 
182      * @see #PATTERN_RFC1123
183      */
184     public static String formatDate(Date date) {
185         return formatDate(date, PATTERN_RFC1123);
186     }
187     
188     /***
189      * Formats the given date according to the specified pattern.  The pattern
190      * must conform to that used by the {@link SimpleDateFormat simple date
191      * format} class.
192      * 
193      * @param date The date to format.
194      * @param pattern The pattern to use for formatting the date.  
195      * @return A formatted date string.
196      * 
197      * @throws IllegalArgumentException If the given date pattern is invalid.
198      * 
199      * @see SimpleDateFormat
200      */
201     public static String formatDate(Date date, String pattern) {
202         if (date == null) throw new IllegalArgumentException("date is null");
203         if (pattern == null) throw new IllegalArgumentException("pattern is null");
204         
205         SimpleDateFormat formatter = new SimpleDateFormat(pattern);
206         return formatter.format(date);
207     }
208     
209     /*** This class should not be instantiated. */    
210     private DateUtil() { }
211     
212 }