FeedReader.java

/*
 * Copyright 2004 Sun Microsystems, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

package com.rometools.fetcher.samples;

import java.net.URL;

import com.rometools.fetcher.FeedFetcher;
import com.rometools.fetcher.FetcherEvent;
import com.rometools.fetcher.FetcherListener;
import com.rometools.fetcher.impl.FeedFetcherCache;
import com.rometools.fetcher.impl.HashMapFeedInfoCache;
import com.rometools.fetcher.impl.HttpURLFeedFetcher;
import com.rometools.rome.feed.synd.SyndFeed;

/**
 * Reads and prints any RSS/Atom feed type. Converted from the original Rome sample FeedReader
 * <p>
 *
 * @author Alejandro Abdelnur
 * @author Nick Lothian
 *
 */
public class FeedReader {

    private FeedReader() {
    }

    public static void main(final String[] args) {

        boolean ok = false;

        if (args.length == 1) {

            try {
                final URL feedUrl = new URL(args[0]);
                final FeedFetcherCache feedInfoCache = HashMapFeedInfoCache.getInstance();
                final FeedFetcher fetcher = new HttpURLFeedFetcher(feedInfoCache);

                final FetcherEventListenerImpl listener = new FetcherEventListenerImpl();

                fetcher.addFetcherEventListener(listener);

                System.err.println("Retrieving feed " + feedUrl);
                // Retrieve the feed.
                // We will get a Feed Polled Event and then a
                // Feed Retrieved event (assuming the feed is valid)
                final SyndFeed feed = fetcher.retrieveFeed(feedUrl);

                System.err.println(feedUrl + " retrieved");
                System.err.println(feedUrl + " has a title: " + feed.getTitle() + " and contains " + feed.getEntries().size() + " entries.");
                // We will now retrieve the feed again. If the feed is unmodified
                // and the server supports conditional gets, we will get a "Feed
                // Unchanged" event after the Feed Polled event
                System.err.println("Polling " + feedUrl + " again to test conditional get support.");
                fetcher.retrieveFeed(feedUrl);
                System.err.println("If a \"Feed Unchanged\" event fired then the server supports conditional gets.");

                ok = true;

            } catch (final Exception ex) {
                System.out.println("ERROR: " + ex.getMessage());
                ex.printStackTrace();
            }

        }

        if (!ok) {
            System.out.println();
            System.out.println("FeedReader reads and prints any RSS/Atom feed type.");
            System.out.println("The first parameter must be the URL of the feed to read.");
            System.out.println();
        }

    }

    static class FetcherEventListenerImpl implements FetcherListener {
        /**
         * @see com.rometools.rome.fetcher.FetcherListener#fetcherEvent(com.rometools.rome.fetcher.FetcherEvent)
         */
        @Override
        public void fetcherEvent(final FetcherEvent event) {
            final String eventType = event.getEventType();
            if (FetcherEvent.EVENT_TYPE_FEED_POLLED.equals(eventType)) {
                System.err.println("\tEVENT: Feed Polled. URL = " + event.getUrlString());
            } else if (FetcherEvent.EVENT_TYPE_FEED_RETRIEVED.equals(eventType)) {
                System.err.println("\tEVENT: Feed Retrieved. URL = " + event.getUrlString());
            } else if (FetcherEvent.EVENT_TYPE_FEED_UNCHANGED.equals(eventType)) {
                System.err.println("\tEVENT: Feed Unchanged. URL = " + event.getUrlString());
            }
        }
    }
}