/*
* Copyright Myrrix Ltd
*
* 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 net.myrrix.web.servlets;
import java.io.IOException;
import java.util.Iterator;
import java.util.NoSuchElementException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.mahout.cf.taste.common.NoSuchItemException;
import org.apache.mahout.cf.taste.common.TasteException;
import org.apache.mahout.cf.taste.recommender.RecommendedItem;
import org.apache.mahout.cf.taste.recommender.Rescorer;
import org.apache.mahout.common.LongPair;
import net.myrrix.common.MyrrixRecommender;
import net.myrrix.common.NotReadyException;
import net.myrrix.common.collection.FastIDSet;
import net.myrrix.online.RescorerProvider;
/**
* <p>Responds to a GET request to {@code /similarity/[itemID1](/[itemID2]/...)?howMany=n(&rescorerParams=...)},
* and in turn calls {@link MyrrixRecommender#mostSimilarItems(long[], int)} with the supplied values.
* If howMany is not specified, defaults to {@link AbstractMyrrixServlet#DEFAULT_HOW_MANY}.</p>
*
* <p>Unknown item IDs are ignored, unless all are unknown, in which case a
* {@link HttpServletResponse#SC_BAD_REQUEST} status is returned.</p>
*
* <p>Outputs item/score pairs in CSV or JSON format, like {@link RecommendServlet} does.</p>
*
* @author Sean Owen
* @since 1.0
*/
public final class SimilarityServlet extends AbstractMyrrixServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
CharSequence pathInfo = request.getPathInfo();
if (pathInfo == null) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, "No path");
return;
}
Iterator<String> pathComponents = SLASH.split(pathInfo).iterator();
FastIDSet itemIDSet = new FastIDSet();
try {
while (pathComponents.hasNext()) {
itemIDSet.add(Long.parseLong(pathComponents.next()));
}
} catch (NoSuchElementException nsee) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, nsee.toString());
return;
} catch (NumberFormatException nfe) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, nfe.toString());
return;
}
if (itemIDSet.isEmpty()) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, "No items");
return;
}
MyrrixRecommender recommender = getRecommender();
RescorerProvider rescorerProvider = getRescorerProvider();
try {
int howMany = getHowMany(request);
Iterable<RecommendedItem> similar;
if (rescorerProvider == null) {
similar = recommender.mostSimilarItems(itemIDSet.toArray(), howMany);
} else {
Rescorer<LongPair> rescorer =
rescorerProvider.getMostSimilarItemsRescorer(recommender, getRescorerParams(request));
similar = recommender.mostSimilarItems(itemIDSet.toArray(),
howMany,
rescorer);
}
output(request, response, similar);
} catch (NoSuchItemException nsie) {
response.sendError(HttpServletResponse.SC_NOT_FOUND, nsie.toString());
} catch (NotReadyException nre) {
response.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE, nre.toString());
} catch (TasteException te) {
response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, te.toString());
getServletContext().log("Unexpected error in " + getClass().getSimpleName(), te);
} catch (IllegalArgumentException iae) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, iae.toString());
}
}
}