/*
* 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.List;
import java.util.NoSuchElementException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.google.common.collect.Lists;
import org.apache.commons.math3.util.Pair;
import org.apache.mahout.cf.taste.common.NoSuchItemException;
import org.apache.mahout.cf.taste.common.TasteException;
import org.apache.mahout.cf.taste.recommender.IDRescorer;
import org.apache.mahout.cf.taste.recommender.RecommendedItem;
import net.myrrix.common.LangUtils;
import net.myrrix.common.MyrrixRecommender;
import net.myrrix.common.NotReadyException;
import net.myrrix.online.RescorerProvider;
/**
* <p>Responds to a GET request to
* {@code /recommendToAnonymous/[itemID1(=value1)](/[itemID2(=value2)]/...)?howMany=n[&rescorerParams=...]},
* and in turn calls {@link MyrrixRecommender#recommendToAnonymous(long[], float[], int, IDRescorer)}
* with the supplied values. That is, 1 or more item IDs are supplied, which may each optionally correspond to
* a value or else default to 1. 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 RecommendToAnonymousServlet 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();
Pair<long[],float[]> itemIDsAndValue;
try {
itemIDsAndValue = parseItemValuePairs(pathComponents);
} 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 (itemIDsAndValue.getFirst().length == 0) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, "No items");
return;
}
long[] itemIDs = itemIDsAndValue.getFirst();
float[] values = itemIDsAndValue.getSecond();
MyrrixRecommender recommender = getRecommender();
RescorerProvider rescorerProvider = getRescorerProvider();
try {
IDRescorer rescorer = rescorerProvider == null ? null :
rescorerProvider.getRecommendToAnonymousRescorer(itemIDs, recommender, getRescorerParams(request));
Iterable<RecommendedItem> recommended =
recommender.recommendToAnonymous(itemIDs, values, getHowMany(request), rescorer);
output(request, response, recommended);
} catch (NotReadyException nre) {
response.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE, nre.toString());
} catch (NoSuchItemException nsie) {
response.sendError(HttpServletResponse.SC_NOT_FOUND, nsie.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());
}
}
static Pair<long[],float[]> parseItemValuePairs(Iterator<String> pathComponents) {
List<Pair<Long,Float>> itemValuePairs = Lists.newArrayListWithCapacity(1);
while (pathComponents.hasNext()) {
itemValuePairs.add(parseItemValue(pathComponents.next()));
}
int size = itemValuePairs.size();
long[] itemIDs = new long[size];
float[] values = new float[size];
for (int i = 0; i < size; i++) {
Pair<Long,Float> itemValuePair = itemValuePairs.get(i);
itemIDs[i] = itemValuePair.getFirst();
Float value = itemValuePair.getSecond();
values[i] = value == null ? 1.0f : value;
}
return new Pair<long[],float[]>(itemIDs, values);
}
private static Pair<Long,Float> parseItemValue(String s) {
int equals = s.indexOf('=');
if (equals < 0) {
return new Pair<Long,Float>(Long.parseLong(s), null);
}
return new Pair<Long,Float>(Long.parseLong(s.substring(0, equals)),
LangUtils.parseFloat(s.substring(equals + 1)));
}
}