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Java > Open Source Codes > com > sun > syndication > io > impl > DateParser


1 /*
2  * Copyright 2004 Sun Microsystems, Inc.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  *
16  */
17 package com.sun.syndication.io.impl;
18
19 import java.text.DateFormat JavaDoc;
20 import java.text.SimpleDateFormat JavaDoc;
21 import java.util.Date JavaDoc;
22 import java.util.TimeZone JavaDoc;
23
24 /**
25  * A helper class that parses Dates out of Strings with date time in RFC822 and W3CDateTime
26  * formats plus the variants Atom (0.3) and RSS (0.9, 0.91, 0.92, 0.93, 0.94, 1.0 and 2.0)
27  * specificators added to those formats.
28  * <p/>
29  * It uses the JDK java.text.SimpleDateFormat class attemtping the parse using a mask for
30  * each one of the possible formats.
31  * <p/>
32  *
33  * @author Alejandro Abdelnur
34  *
35  */
36 public class DateParser {
37
38     // order is like this because the SimpleDateFormat.parse does not fail with exception
39 // if it can parse a valid date out of a substring of the full string given the mask
40 // so we have to check the most complete format first, then it fails with exception
41 private static final String JavaDoc[] RFC822_MASKS = {
42         "EEE, dd MMM yyyy HH:mm:ss z",
43         "EEE, dd MMM yyyy HH:mm z",
44         "EEE, dd MMM yy HH:mm:ss z",
45         "EEE, dd MMM yy HH:mm z",
46         "dd MMM yyyy HH:mm:ss z",
47         "dd MMM yyyy HH:mm z",
48         "dd MMM yy HH:mm:ss z",
49         "dd MMM yy HH:mm z"
50     };
51
52     // order is like this because the SimpleDateFormat.parse does not fail with exception
53 // if it can parse a valid date out of a substring of the full string given the mask
54 // so we have to check the most complete format first, then it fails with exception
55 private static final String JavaDoc[] W3CDATETIME_MASKS = {
56         "yyyy-MM-dd'T'HH:mm:ssz",
57         "yyyy-MM-dd'T'HH:mmz",
58         "yyyy-MM-dd",
59         "yyyy-MM",
60         "yyyy"
61     };
62
63     /**
64      * Private constructor to avoid DateParser instances creation.
65      */
66     private DateParser() {
67     }
68
69     /**
70      * Parses a Date out of a string using an array of masks.
71      * <p/>
72      * It uses the masks in order until one of them succedes or all fail.
73      * <p/>
74      *
75      * @param masks array of masks to use for parsing the string
76      * @param sDate string to parse for a date.
77      * @return the Date represented by the given string using one of the given masks.
78      * It returns <b>null</b> if it was not possible to parse the the string with any of the masks.
79      *
80      */
81     private static Date JavaDoc parseUsingMask(String JavaDoc[] masks,String JavaDoc sDate) {
82         Date JavaDoc d = null;
83         for (int i=0;d==null && i<masks.length;i++) {
84             DateFormat JavaDoc df = new SimpleDateFormat JavaDoc(masks[i]);
85             df.setLenient(true);
86             try {
87                 d = df.parse(sDate);
88 // System.out.println("s: "+sDate+" m: "+masks[i]+" d: "+d);
89 }
90             catch (Exception JavaDoc ex1) {
91 // System.out.println("s: "+sDate+" m: "+masks[i]+" d: "+null);
92 }
93         }
94         return d;
95     }
96
97     /**
98      * Parses a Date out of a String with a date in RFC822 format.
99      * <p/>
100      * It parsers the following formats:
101      * <ul>
102      * <li>"EEE, dd MMM yyyy HH:mm:ss z"</li>
103      * <li>"EEE, dd MMM yyyy HH:mm z"</li>
104      * <li>"EEE, dd MMM yy HH:mm:ss z"</li>
105      * <li>"EEE, dd MMM yy HH:mm z"</li>
106      * <li>"dd MMM yyyy HH:mm:ss z"</li>
107      * <li>"dd MMM yyyy HH:mm z"</li>
108      * <li>"dd MMM yy HH:mm:ss z"</li>
109      * <li>"dd MMM yy HH:mm z"</li>
110      * </ul>
111      * <p/>
112      * Refer to the java.text.SimpleDateFormat javadocs for details on the format of each element.
113      * <p/>
114      * @param sDate string to parse for a date.
115      * @return the Date represented by the given RFC822 string.
116      * It returns <b>null</b> if it was not possible to parse the given string into a Date.
117      *
118      */
119     public static Date JavaDoc parseRFC822(String JavaDoc sDate) {
120         return parseUsingMask(RFC822_MASKS,sDate);
121     }
122
123
124     /**
125      * Parses a Date out of a String with a date in W3C date-time format.
126      * <p/>
127      * It parsers the following formats:
128      * <ul>
129      * <li>"yyyy-MM-dd'T'HH:mm:ssz"</li>
130      * <li>"yyyy-MM-dd'T'HH:mmz"</li>
131      * <li>"yyyy-MM-dd"</li>
132      * <li>"yyyy-MM"</li>
133      * <li>"yyyy"</li>
134      * </ul>
135      * <p/>
136      * Refer to the java.text.SimpleDateFormat javadocs for details on the format of each element.
137      * <p/>
138      * @param sDate string to parse for a date.
139      * @return the Date represented by the given W3C date-time string.
140      * It returns <b>null</b> if it was not possible to parse the given string into a Date.
141      *
142      */
143     public static Date JavaDoc parseW3CDateTime(String JavaDoc sDate) {
144         // if sDate has time on it, it injects 'GTM' before de TZ displacement to
145 // allow the SimpleDateFormat parser to parse it properly
146 int tIndex = sDate.indexOf("T");
147         if (tIndex>-1) {
148             if (sDate.endsWith("Z")) {
149                 sDate = sDate.substring(0,sDate.length()-1)+"+00:00";
150             }
151             int tzdIndex = sDate.indexOf("+",tIndex);
152             if (tzdIndex==-1) {
153                 tzdIndex = sDate.indexOf("-",tIndex);
154             }
155             if (tzdIndex>-1) {
156                 String JavaDoc pre = sDate.substring(0,tzdIndex);
157                 int secFraction = pre.indexOf(",");
158                 if (secFraction>-1) {
159                     pre = pre.substring(0,secFraction);
160                 }
161                 String JavaDoc post = sDate.substring(tzdIndex);
162                 sDate = pre + "GMT" + post;
163             }
164         }
165         return parseUsingMask(W3CDATETIME_MASKS,sDate);
166     }
167
168     /**
169      * create a RFC822 representation of a date.
170      * <p/>
171      * Refer to the java.text.SimpleDateFormat javadocs for details on the format of each element.
172      * <p/>
173      * @param date Date to parse
174      * @return the RFC822 represented by the given Date
175      * It returns <b>null</b> if it was not possible to parse the date.
176      *
177      */
178     public static String JavaDoc formatRFC822(Date JavaDoc date) {
179         SimpleDateFormat JavaDoc dateFormater = new SimpleDateFormat JavaDoc("EEE, dd MMM yyyy HH:mm:ss 'GMT'");
180         dateFormater.setTimeZone(TimeZone.getTimeZone("GMT"));
181         return dateFormater.format(date);
182     }
183
184     /**
185      * create a W3C Date Time representation of a date.
186      * <p/>
187      * Refer to the java.text.SimpleDateFormat javadocs for details on the format of each element.
188      * <p/>
189      * @param date Date to parse
190      * @return the W3C Date Time represented by the given Date
191      * It returns <b>null</b> if it was not possible to parse the date.
192      *
193      */
194     public static String JavaDoc formatW3CDateTime(Date JavaDoc date) {
195         SimpleDateFormat JavaDoc dateFormater = new SimpleDateFormat JavaDoc("yyyy-MM-dd'T'HH:mm:ss'Z'");
196         dateFormater.setTimeZone(TimeZone.getTimeZone("GMT"));
197         return dateFormater.format(date);
198     }
199
200 }
201
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