FeedDiscovery.java

/*
 * PROPRIETARY and CONFIDENTIAL
 * 
 * Copyright 2012 Magellan Distribution Corporation
 * 
 * All rights reserved.
 */
package com.ajah.syndicate.fetch;

import java.io.IOException;

import lombok.extern.java.Log;

import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.util.EntityUtils;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import com.ajah.spring.jdbc.err.DataOperationException;
import com.ajah.syndicate.FeedSource;
import com.ajah.syndicate.data.FeedEntryManager;
import com.ajah.syndicate.data.FeedManager;
import com.ajah.syndicate.data.FeedSourceManager;

/**
 * Simple utility for finding {@link FeedSource}s.
 * 
 * @author <a href="http://efsavage.com">Eric F. Savage</a>, <a
 *         href="mailto:code@efsavage.com">code@efsavage.com</a>.
 */
@Log
@Component
public class FeedDiscovery {

	@Autowired
	FeedSourceManager feedSourceManager;

	@Autowired
	FeedManager feedManager;

	@Autowired
	FeedEntryManager entryManager;

	/**
	 * Pulls a page and attempts to discover a feed for it via
	 * link[rel='alternate'].
	 * 
	 * @param url
	 *            The URL of the page to try and discover the feed for.
	 * @return The feedsource if matched or created, may be null.
	 * @throws ClientProtocolException
	 *             If the page could not be pulled.
	 * @throws IOException
	 *             If the page could not be pulled.
	 * @throws DataOperationException
	 *             If a query could not be executed.
	 */
	public FeedSource discover(final String url) throws ClientProtocolException, IOException, DataOperationException {
		log.fine("Discovering feed for " + url);
		try (final CloseableHttpClient client = HttpClientBuilder.create().build()) {
			final HttpGet get = new HttpGet(url);
			try (final CloseableHttpResponse response = client.execute(get)) {
				final String html = EntityUtils.toString(response.getEntity());
				final Document doc = Jsoup.parse(html);
				final Elements alternateLinks = doc.select("link");
				for (final Element alternateLink : alternateLinks) {
					if ("alternate".equals(alternateLink.attr("rel"))) {
						if ("application/rss+xml".equals(alternateLink.attr("type"))) {
							log.fine("Found rss link " + alternateLink.attr("href"));
							final String rss = alternateLink.attr("href");
							return this.feedSourceManager.findOrCreateByFeedUrl(rss);
						}
						log.fine("Found alternate link " + alternateLink.html());
					} else {
						log.fine("Found link " + alternateLink.html());
					}
				}
			}
		}
		return null;
	}
}