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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 /***
43 * A utility class for parsing and formatting HTTP dates as used in cookies and
44 * other headers. This class handles dates as defined by RFC 2616 section
45 * 3.3.1 as well as some other common non-standard formats.
46 *
47 * @author Christopher Brown
48 * @author Michael Becke
49 */
50 public class DateUtil {
51
52 /***
53 * Date format pattern used to parse HTTP date headers in RFC 1123 format.
54 */
55 public static final String PATTERN_RFC1123 = "EEE, dd MMM yyyy HH:mm:ss zzz";
56
57 /***
58 * Date format pattern used to parse HTTP date headers in RFC 1036 format.
59 */
60 public static final String PATTERN_RFC1036 = "EEEE, dd-MMM-yy HH:mm:ss zzz";
61
62 /***
63 * Date format pattern used to parse HTTP date headers in ANSI C
64 * <code>asctime()</code> format.
65 */
66 public static final String PATTERN_ASCTIME = "EEE MMM d HH:mm:ss yyyy";
67
68 private static final Collection DEFAULT_PATTERNS = Arrays.asList(
69 new String[] { PATTERN_ASCTIME, PATTERN_RFC1036, PATTERN_RFC1123 } );
70
71 private static final Date DEFAULT_TWO_DIGIT_YEAR_START;
72
73 static {
74 Calendar calendar = Calendar.getInstance();
75 calendar.set(2000, Calendar.JANUARY, 1, 0, 0);
76 DEFAULT_TWO_DIGIT_YEAR_START = calendar.getTime();
77 }
78
79 private static final TimeZone GMT = TimeZone.getTimeZone("GMT");
80
81 /***
82 * Parses a date value. The formats used for parsing the date value are retrieved from
83 * the default http params.
84 *
85 * @param dateValue the date value to parse
86 *
87 * @return the parsed date
88 *
89 * @throws DateParseException if the value could not be parsed using any of the
90 * supported date formats
91 */
92 public static Date parseDate(String dateValue) throws DateParseException {
93 return parseDate(dateValue, null, null);
94 }
95
96 /***
97 * Parses the date value using the given date formats.
98 *
99 * @param dateValue the date value to parse
100 * @param dateFormats the date formats to use
101 *
102 * @return the parsed date
103 *
104 * @throws DateParseException if none of the dataFormats could parse the dateValue
105 */
106 public static Date parseDate(String dateValue, Collection dateFormats)
107 throws DateParseException {
108 return parseDate(dateValue, dateFormats, null);
109 }
110
111 /***
112 * Parses the date value using the given date formats.
113 *
114 * @param dateValue the date value to parse
115 * @param dateFormats the date formats to use
116 * @param startDate During parsing, two digit years will be placed in the range
117 * <code>startDate</code> to <code>startDate + 100 years</code>. This value may
118 * be <code>null</code>. When <code>null</code> is given as a parameter, year
119 * <code>2000</code> will be used.
120 *
121 * @return the parsed date
122 *
123 * @throws DateParseException if none of the dataFormats could parse the dateValue
124 */
125 public static Date parseDate(
126 String dateValue,
127 Collection dateFormats,
128 Date startDate
129 ) throws DateParseException {
130
131 if (dateValue == null) {
132 throw new IllegalArgumentException("dateValue is null");
133 }
134 if (dateFormats == null) {
135 dateFormats = DEFAULT_PATTERNS;
136 }
137 if (startDate == null) {
138 startDate = DEFAULT_TWO_DIGIT_YEAR_START;
139 }
140
141
142 if (dateValue.length() > 1
143 && dateValue.startsWith("'")
144 && dateValue.endsWith("'")
145 ) {
146 dateValue = dateValue.substring (1, dateValue.length() - 1);
147 }
148
149 SimpleDateFormat dateParser = null;
150 Iterator formatIter = dateFormats.iterator();
151
152 while (formatIter.hasNext()) {
153 String format = (String) formatIter.next();
154 if (dateParser == null) {
155 dateParser = new SimpleDateFormat(format, Locale.US);
156 dateParser.setTimeZone(TimeZone.getTimeZone("GMT"));
157 dateParser.set2DigitYearStart(startDate);
158 } else {
159 dateParser.applyPattern(format);
160 }
161 try {
162 return dateParser.parse(dateValue);
163 } catch (ParseException pe) {
164
165 }
166 }
167
168
169 throw new DateParseException("Unable to parse the date " + dateValue);
170 }
171
172 /***
173 * Formats the given date according to the RFC 1123 pattern.
174 *
175 * @param date The date to format.
176 * @return An RFC 1123 formatted date string.
177 *
178 * @see #PATTERN_RFC1123
179 */
180 public static String formatDate(Date date) {
181 return formatDate(date, PATTERN_RFC1123);
182 }
183
184 /***
185 * Formats the given date according to the specified pattern. The pattern
186 * must conform to that used by the {@link SimpleDateFormat simple date
187 * format} class.
188 *
189 * @param date The date to format.
190 * @param pattern The pattern to use for formatting the date.
191 * @return A formatted date string.
192 *
193 * @throws IllegalArgumentException If the given date pattern is invalid.
194 *
195 * @see SimpleDateFormat
196 */
197 public static String formatDate(Date date, String pattern) {
198 if (date == null) throw new IllegalArgumentException("date is null");
199 if (pattern == null) throw new IllegalArgumentException("pattern is null");
200
201 SimpleDateFormat formatter = new SimpleDateFormat(pattern, Locale.US);
202 formatter.setTimeZone(GMT);
203 return formatter.format(date);
204 }
205
206 /*** This class should not be instantiated. */
207 private DateUtil() { }
208
209 }