Package net.myrrix.web.servlets

Source Code of net.myrrix.web.servlets.EstimateForAnonymousServlet

/*
* 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.NoSuchElementException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.math3.util.Pair;
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 /estimateForAnonymous/[toItemID]/[itemID1(=value1)](/[itemID2(=value2)]/...)},
* and in turn calls {@link MyrrixRecommender#estimateForAnonymous(long, long[], float[])}
* 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.</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 the result of the method call as a value on one line.</p>
*
* @author Sean Owen
* @since 1.0
*/
public final class EstimateForAnonymousServlet 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;
    Pair<long[],float[]> itemIDsAndValue;
    try {
      toItemID = Long.parseLong(pathComponents.next());
      itemIDsAndValue = RecommendToAnonymousServlet.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();
    try {
      float estimate = recommender.estimateForAnonymous(toItemID, itemIDs, values);
      Writer out = response.getWriter();
      out.write(Float.toString(estimate));
      out.write('\n');
    } 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);
    }
  }

}
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