001/**
002 * Copyright (c) 2011, The University of Southampton and the individual contributors.
003 * All rights reserved.
004 *
005 * Redistribution and use in source and binary forms, with or without modification,
006 * are permitted provided that the following conditions are met:
007 *
008 *   *  Redistributions of source code must retain the above copyright notice,
009 *      this list of conditions and the following disclaimer.
010 *
011 *   *  Redistributions in binary form must reproduce the above copyright notice,
012 *      this list of conditions and the following disclaimer in the documentation
013 *      and/or other materials provided with the distribution.
014 *
015 *   *  Neither the name of the University of Southampton nor the names of its
016 *      contributors may be used to endorse or promote products derived from this
017 *      software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
020 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
021 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
022 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
023 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
026 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
028 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030package org.openimaj.stream.functions;
031
032import java.net.URL;
033import java.util.ArrayList;
034import java.util.Arrays;
035import java.util.List;
036
037import org.apache.log4j.Logger;
038import org.openimaj.util.function.MultiFunction;
039import org.openimaj.web.scraping.SiteSpecificConsumer;
040
041/**
042 * This class implements a function that will given an input URL outputs a list
043 * of URLs based on applying a list of {@link SiteSpecificConsumer}s to the
044 * input.
045 * 
046 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
047 */
048public class SiteSpecificURLExtractor implements MultiFunction<URL, URL> {
049        private static final Logger logger = Logger.getLogger(SiteSpecificURLExtractor.class);
050
051        /**
052         * the site specific consumers
053         */
054        protected List<SiteSpecificConsumer> siteSpecific = new ArrayList<SiteSpecificConsumer>();
055
056        /**
057         * Construct with the given list of consumers.
058         * 
059         * @param consumers
060         *            the consumers
061         */
062        public SiteSpecificURLExtractor(List<SiteSpecificConsumer> consumers) {
063                this.siteSpecific = consumers;
064        }
065
066        /**
067         * Construct with the given consumers.
068         * 
069         * @param consumers
070         *            the consumers
071         */
072        public SiteSpecificURLExtractor(SiteSpecificConsumer... consumers) {
073                this.siteSpecific = Arrays.asList(consumers);
074        }
075
076        /**
077         * Construct with empty list of consumers.
078         */
079        protected SiteSpecificURLExtractor() {
080                this.siteSpecific = new ArrayList<SiteSpecificConsumer>();
081        }
082
083        @Override
084        public List<URL> apply(URL in) {
085                final List<URL> imageUrls = processURLs(in);
086
087                if (imageUrls == null)
088                        return new ArrayList<URL>();
089
090                return imageUrls;
091        }
092
093        /**
094         * First, try all the {@link SiteSpecificConsumer} instances loaded into
095         * {@link #siteSpecific}. If any consumer takes control of a link the
096         * consumer's output is used
097         * 
098         * if this fails use
099         * {@link HttpUtils#readURLAsByteArrayInputStream(URL, org.apache.http.client.RedirectStrategy)}
100         * with a {@link StatusConsumerRedirectStrategy} which specifically
101         * disallows redirects to be dealt with automatically and forces this
102         * function to be called for each redirect.
103         * 
104         * @param url
105         * @return a list of images or null
106         */
107        protected List<URL> processURLs(URL url) {
108                logger.debug("Resolving URL: " + url);
109                logger.debug("Attempting site specific consumers");
110
111                for (final SiteSpecificConsumer consumer : siteSpecific) {
112                        if (consumer.canConsume(url)) {
113                                logger.debug("Site specific consumer: " + consumer.getClass().getName() + " working on link");
114                                final List<URL> urlList = consumer.consume(url);
115
116                                if (urlList != null && !urlList.isEmpty()) {
117                                        logger.debug("Site specific consumer returned non-null, returning the URLs");
118
119                                        return urlList;
120                                }
121                        }
122                }
123                return null;
124        }
125}