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1   /*
2    * $Header: /home/cvs/jakarta-commons/httpclient/src/java/org/apache/commons/httpclient/util/DateParser.java,v 1.9 2004/04/18 23:51:38 jsdever Exp $
3    * $Revision: 1.9 $
4    * $Date: 2004/04/18 23:51:38 $
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.httpclient.params.DefaultHttpParams;
42  import org.apache.commons.logging.Log;
43  import org.apache.commons.logging.LogFactory;
44  
45  /***
46   * A utility class for parsing HTTP dates as used in cookies and other headers.  
47   * This class handles dates as defined by RFC 2616 section 3.3.1 as well as 
48   * some other common non-standard formats.
49   * 
50   * @author Christopher Brown
51   * @author Michael Becke
52   */
53  public class DateParser {
54  
55      /*** Log object for this class. */
56      private static final Log LOG = LogFactory.getLog(DateParser.class);
57  
58      /***
59       * The key used to look up the date patterns used for parsing.  The String patterns are stored
60       * in a {@link Collection} and must be compatible with {@link SimpleDateFormat}.
61       * 
62       * @see org.apache.commons.httpclient.params.DefaultHttpParams
63       */
64      public static final String KEY_DATE_PATTERNS = "http.dateParser.patterns";
65  
66      /***
67       * Date format pattern used to parse HTTP date headers in RFC 1123 format.
68       */
69      public static final String PATTERN_RFC1123 = "EEE, dd MMM yyyy HH:mm:ss zzz";
70  
71      /***
72       * Date format pattern used to parse HTTP date headers in RFC 1036 format.
73       */
74      public static final String PATTERN_RFC1036 = "EEEE, dd-MMM-yy HH:mm:ss zzz";
75  
76      /***
77       * Date format pattern used to parse HTTP date headers in ANSI C 
78       * <code>asctime()</code> format.
79       */
80      public static final String PATTERN_ASCTIME = "EEE MMM d HH:mm:ss yyyy";
81  
82      /***
83       * Parses a date value.  The formats used for parsing the date value are retrieved from
84       * the default http params.
85       *
86       * @param dateValue the date value to parse
87       * 
88       * @return the parsed date
89       *
90       * @throws DateParseException if the value could not be parsed using any of the 
91       * supported date formats
92       * 
93       * @see DefaultHttpParams#getDefaultParams()
94       */
95      public static Date parseDate(String dateValue) throws DateParseException {
96          
97          Collection patterns = (Collection) DefaultHttpParams.getDefaultParams().getParameter(
98              KEY_DATE_PATTERNS
99          );
100         if (patterns == null) {
101             LOG.warn("DateParser patterns not included in the default params.");
102             patterns = Arrays.asList(
103                 new String[] { PATTERN_ASCTIME, PATTERN_RFC1036, PATTERN_RFC1123 }
104             );
105         }
106         return parseDate(dateValue, patterns);
107     }
108     
109     /***
110      * Parses the date value using the given date formats.
111      * 
112      * @param dateValue the date value to parse
113      * @param dateFormats the date formats to use
114      * 
115      * @return the parsed date
116      * 
117      * @throws DateParseException if none of the dataFormats could parse the dateValue
118      */
119     private static Date parseDate(
120         String dateValue, 
121         Collection dateFormats
122     ) throws DateParseException {
123         
124         if (dateValue == null) {
125             throw new IllegalArgumentException("dateValue is null");
126         }
127 
128         // trim single quotes around date if present
129         // see http://nagoya.apache.org/bugzilla/show_bug.cgi?id=5279
130         if (dateValue.length() > 1 
131             && dateValue.startsWith("'") 
132             && dateValue.endsWith("'")
133         ) {
134             dateValue = dateValue.substring (1, dateValue.length() - 1);
135         }
136         
137         SimpleDateFormat dateParser = null;        
138         Iterator formatIter = dateFormats.iterator();
139         
140         while (formatIter.hasNext()) {
141             String format = (String) formatIter.next();            
142             if (dateParser == null) {
143                 dateParser = new SimpleDateFormat(format, Locale.US);
144                 dateParser.setTimeZone(TimeZone.getTimeZone("GMT"));
145             } else {
146                 dateParser.applyPattern(format);                    
147             }
148             try {
149                 return dateParser.parse(dateValue);
150             } catch (ParseException pe) {
151                 // ignore this exception, we will try the next format
152             }                
153         }
154         
155         // we were unable to parse the date
156         throw new DateParseException("Unable to parse the date " + dateValue);        
157     }
158 
159     /*** This class should not be instantiated. */    
160     private DateParser() { }
161     
162 }