2 * rhynodge - HttpQueryFilter.java - Copyright © 2013 David Roden
4 * This program is free software: you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation, either version 3 of the License, or
7 * (at your option) any later version.
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program. If not, see <http://www.gnu.org/licenses/>.
18 package net.pterodactylus.rhynodge.filters;
20 import static com.google.common.base.Preconditions.*;
22 import net.pterodactylus.rhynodge.Filter;
23 import net.pterodactylus.rhynodge.State;
24 import net.pterodactylus.rhynodge.states.FailedState;
25 import net.pterodactylus.rhynodge.states.HtmlState;
26 import net.pterodactylus.rhynodge.states.StringState;
28 import com.google.common.base.Optional;
29 import org.jsoup.nodes.Document;
32 * {@link Filter} implementation that extracts a URL from an {@link HtmlState}.
34 * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
36 public abstract class ExtractUrlFilter implements Filter {
39 public State filter(State state) {
40 checkArgument(state instanceof HtmlState, "state must be an HTML state");
42 HtmlState htmlState = (HtmlState) state;
43 Optional<String> newUrl = extractUrl(htmlState.document());
45 if (!newUrl.isPresent()) {
46 return new FailedState();
49 return new StringState(newUrl.get());
57 * Extracts the URL from the given document. If the returned value is {@link
58 * Optional#absent()}, {@link #filter(State)} will return a {@link
62 * The document to extract the URL from
63 * @return The extracted URL, or {@link Optional#absent()}
65 protected abstract Optional<String> extractUrl(Document document);