001 /*
002 * Copyright 1999,2004 The Apache Software Foundation.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017 package org.apache.commons.feedparser.locate;
018
019 import java.util.HashMap;
020 import java.util.HashSet;
021 import java.util.List;
022 import java.util.regex.Matcher;
023 import java.util.regex.Pattern;
024
025 import org.apache.commons.feedparser.FeedList;
026 import org.apache.log4j.Logger;
027
028 /**
029 *
030 * http://www.ietf.org/internet-drafts/draft-ietf-atompub-autodiscovery-00.txt
031 *
032 * @author <a href="mailto:burton@apache.org">Kevin A. Burton</a>
033 */
034 public class DiscoveryLocator {
035
036 private static Logger log = Logger.getLogger( DiscoveryLocator.class );
037
038 /**
039 * Get a FULL link within the content. We then pull the attributes out of
040 * this.
041 */
042 static Pattern element_pattern =
043 Pattern.compile( "<link[^>]+",
044 Pattern.CASE_INSENSITIVE );
045
046 /**
047 * Regex to match on attributes.
048 *
049 * Implementation: Mon Mar 14 2005 01:59 PM (burton@rojo.com): this is a
050 * pretty difficult regexp to grok.
051 *
052 * There's are two regexps here. One for attributes with quotes and one
053 * without. Each regexp has two groups - 1 is the name and 2 is the value.
054 * You can split the regexp on | to better understand each individual
055 * regexp.
056 */
057
058 // > Attribute values MUST be one of the following: enclosed in double
059 // > quotes, enclosed in single quotes, or not enclosed in quotes at all.
060 //
061 //
062 static String ATTR_REGEXP = "([a-zA-Z]+)=[\"']([^\"']+)[\"']|([a-zA-Z]+)=([^\"'>\r\n\t ]+)";
063
064 static Pattern ATTR_PATTERN = Pattern.compile( ATTR_REGEXP,
065 Pattern.CASE_INSENSITIVE );
066
067 static HashSet mediatypes = new HashSet();
068
069 static {
070
071 mediatypes.add( FeedReference.ATOM_MEDIA_TYPE );
072 mediatypes.add( FeedReference.RSS_MEDIA_TYPE );
073 mediatypes.add( FeedReference.XML_MEDIA_TYPE );
074
075 }
076
077 /**
078 * Locate a feed via RSS/Atom auto-discovery. If both Atom and RSS are
079 * listed we return both. Actually we return all Atom/RSS or XML feeds
080 * including FOAF. It's up to the caller to use the correct feed.
081 *
082 *
083 */
084 public static final List locate( String resource,
085 String content,
086 FeedList list )
087 throws Exception {
088
089 //this mechanism is easier but it isn't efficient. I should just parse
090 //elements forward until I discover </head>. Also note that this isn't
091 //doing all feed URLs just the first ones it finds.
092
093 Matcher m = element_pattern.matcher( content );
094
095 while( m.find() ) {
096 //the value of the link element XML... example:
097
098 // <link rel="alternate"
099 // href="http://www.codinginparadise.org/weblog/atom.xml"
100 // type="application/atom+xml"
101 // title="ATOM" />
102
103 String element = m.group( 0 );
104
105 HashMap attributes = getAttributes( element );
106
107 String type = (String)attributes.get( "type" );
108 if (type != null)
109 type = type.toLowerCase();
110
111 if ( mediatypes.contains( type ) ) {
112
113 //expand the href
114 String href = (String)attributes.get( "href" );
115 log.debug("href="+href);
116
117 // http://xml.coverpages.org/draft-ietf-atompub-autodiscovery-00.txt
118
119 // > The href attribute MUST be present in an Atom autodiscovery element,
120 // > and its value MUST be the URI [RFC2396] of an Atom feed. The value
121 // > MAY be a relative URI, and if so, clients MUST resolve it to a full
122 // > URI (section 5 of [RFC2396]) using the document's base URI (section
123 // > 12.4 of HTML 4 [W3C.REC-html401-19991224]).
124
125 href = ResourceExpander.expand( resource, href );
126
127 FeedReference feedReference = new FeedReference( href, type );
128
129 feedReference.title = (String)attributes.get( "title" );
130
131 list.add( feedReference );
132
133 if ( type.equals( FeedReference.ATOM_MEDIA_TYPE ) )
134 list.setFirstAdAtomFeed( feedReference );
135
136 if ( type.equals( FeedReference.RSS_MEDIA_TYPE ) )
137 list.setFirstAdRSSFeed( feedReference );
138
139 }
140
141 }
142
143 return list;
144
145 }
146
147 /**
148 * Parse attributes within elements into a hashmap.
149 *
150 *
151 */
152 public static HashMap getAttributes( String content ) {
153
154 HashMap map = new HashMap();
155
156 Matcher m = ATTR_PATTERN.matcher( content );
157
158 int index = 0;
159
160 while ( m.find( index ) ) {
161
162 String name = m.group( 1 );
163 String value = null;
164
165 //Since we use an OR regexp the first match will be 1/2 and the
166 //second will be 3/4
167 if ( name != null ) {
168 value = m.group( 2 );
169 } else {
170 name = m.group( 3 );
171 value = m.group( 4 );
172 }
173
174 //String value = m.group( 2 ).toLowerCase().trim();
175 name = name.toLowerCase().trim();
176 // Some services, such as AOL LiveJournal, are case sensitive
177 // on their resource names; can't do a toLowerCase.
178 // Brad Neuberg, bkn3@columbia.edu
179 // String value = m.group( 2 ).toLowerCase().trim();
180 value = value.trim();
181
182 if ( "".equals( value ) )
183 value = null;
184
185 map.put( name, value );
186
187 index = m.end();
188
189 }
190
191 return map;
192
193 }
194
195 }