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1   /*
2    * $Header: /home/cvs/jakarta-commons/httpclient/src/java/org/apache/commons/httpclient/util/DateUtil.java,v 1.1 2004/11/06 19:15:42 mbecke Exp $
3    * $Revision: 1.1 $
4    * $Date: 2004/11/06 19:15:42 $
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.Collection;
36  import java.util.Date;
37  import java.util.Iterator;
38  import java.util.Locale;
39  import java.util.TimeZone;
40  
41  import org.apache.commons.logging.Log;
42  import org.apache.commons.logging.LogFactory;
43  
44  /***
45   * A utility class for parsing and formatting HTTP dates as used in cookies and 
46   * other headers.  This class handles dates as defined by RFC 2616 section 
47   * 3.3.1 as well as some other common non-standard formats.
48   * 
49   * @author Christopher Brown
50   * @author Michael Becke
51   */
52  public class DateUtil {
53  
54      /*** Log object for this class. */
55      private static final Log LOG = LogFactory.getLog(DateUtil.class);
56  
57      /***
58       * Date format pattern used to parse HTTP date headers in RFC 1123 format.
59       */
60      public static final String PATTERN_RFC1123 = "EEE, dd MMM yyyy HH:mm:ss zzz";
61  
62      /***
63       * Date format pattern used to parse HTTP date headers in RFC 1036 format.
64       */
65      public static final String PATTERN_RFC1036 = "EEEE, dd-MMM-yy HH:mm:ss zzz";
66  
67      /***
68       * Date format pattern used to parse HTTP date headers in ANSI C 
69       * <code>asctime()</code> format.
70       */
71      public static final String PATTERN_ASCTIME = "EEE MMM d HH:mm:ss yyyy";
72  
73      private static final Collection DEFAULT_PATTERNS = Arrays.asList(
74      		new String[] { PATTERN_ASCTIME, PATTERN_RFC1036, PATTERN_RFC1123 } );
75      
76      /***
77       * Parses a date value.  The formats used for parsing the date value are retrieved from
78       * the default http params.
79       *
80       * @param dateValue the date value to parse
81       * 
82       * @return the parsed date
83       *
84       * @throws DateParseException if the value could not be parsed using any of the 
85       * supported date formats
86       */
87      public static Date parseDate(String dateValue) throws DateParseException {
88          return parseDate(dateValue, null);
89      }
90      
91      /***
92       * Parses the date value using the given date formats.
93       * 
94       * @param dateValue the date value to parse
95       * @param dateFormats the date formats to use
96       * 
97       * @return the parsed date
98       * 
99       * @throws DateParseException if none of the dataFormats could parse the dateValue
100      */
101     public static Date parseDate(
102         String dateValue, 
103         Collection dateFormats
104     ) throws DateParseException {
105         
106         if (dateValue == null) {
107             throw new IllegalArgumentException("dateValue is null");
108         }
109         if (dateFormats == null) {
110         	dateFormats = DEFAULT_PATTERNS;
111         }
112         // trim single quotes around date if present
113         // see http://nagoya.apache.org/bugzilla/show_bug.cgi?id=5279
114         if (dateValue.length() > 1 
115             && dateValue.startsWith("'") 
116             && dateValue.endsWith("'")
117         ) {
118             dateValue = dateValue.substring (1, dateValue.length() - 1);
119         }
120         
121         SimpleDateFormat dateParser = null;        
122         Iterator formatIter = dateFormats.iterator();
123         
124         while (formatIter.hasNext()) {
125             String format = (String) formatIter.next();            
126             if (dateParser == null) {
127                 dateParser = new SimpleDateFormat(format, Locale.US);
128                 dateParser.setTimeZone(TimeZone.getTimeZone("GMT"));
129             } else {
130                 dateParser.applyPattern(format);                    
131             }
132             try {
133                 return dateParser.parse(dateValue);
134             } catch (ParseException pe) {
135                 // ignore this exception, we will try the next format
136             }                
137         }
138         
139         // we were unable to parse the date
140         throw new DateParseException("Unable to parse the date " + dateValue);        
141     }
142 
143     /***
144      * Formats the given date according to the RFC 1123 pattern.
145      * 
146      * @param date The date to format.
147      * @return An RFC 1123 formatted date string.
148      * 
149      * @see #PATTERN_RFC1123
150      */
151     public static String formatDate(Date date) {
152         return formatDate(date, PATTERN_RFC1123);
153     }
154     
155     /***
156      * Formats the given date according to the specified pattern.  The pattern
157      * must conform to that used by the {@link SimpleDateFormat simple date
158      * format} class.
159      * 
160      * @param date The date to format.
161      * @param pattern The pattern to use for formatting the date.  
162      * @return A formatted date string.
163      * 
164      * @throws IllegalArgumentException If the given date pattern is invalid.
165      * 
166      * @see SimpleDateFormat
167      */
168     public static String formatDate(Date date, String pattern) {
169         if (date == null) throw new IllegalArgumentException("date is null");
170         if (pattern == null) throw new IllegalArgumentException("pattern is null");
171         
172         SimpleDateFormat formatter = new SimpleDateFormat(pattern);
173         return formatter.format(date);
174     }
175     
176     /*** This class should not be instantiated. */    
177     private DateUtil() { }
178     
179 }