/*
* 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.io.Writer;
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.mahout.cf.taste.common.NoSuchItemException;
import org.apache.mahout.cf.taste.common.TasteException;
import net.myrrix.common.MyrrixRecommender;
import net.myrrix.common.NotReadyException;
/**
* <p>Responds to a GET request to {@code /similarityToItem/[toItemID]/itemID1(/[itemID2]/...)},
* and in turn calls {@link MyrrixRecommender#similarityToItem(long, long...)} with the supplied values.</p>
*
* <p>Unknown item IDs are ignored, unless all are unknown or {@code toItemID} is unknown, in which case a
* {@link HttpServletResponse#SC_BAD_REQUEST} status is returned.</p>
*
* <p>The output are similarities, in the same order as the item IDs, one per line.</p>
*
* @author Sean Owen
* @since 1.0
*/
public final class SimilarityToItemServlet 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();
long toItemID;
List<Long> itemIDsList = Lists.newArrayList();
try {
toItemID = Long.parseLong(pathComponents.next());
while (pathComponents.hasNext()) {
itemIDsList.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 (itemIDsList.isEmpty()) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, "No items");
return;
}
long[] itemIDs = new long[itemIDsList.size()];
for (int i = 0; i < itemIDs.length; i++) {
itemIDs[i] = itemIDsList.get(i);
}
MyrrixRecommender recommender = getRecommender();
try {
float[] similarities = recommender.similarityToItem(toItemID, itemIDs);
Writer out = response.getWriter();
for (float similarity : similarities) {
out.write(Float.toString(similarity));
out.write('\n');
}
} 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);
}
}
}