gistfile1.java

package org.bg.server;

import java.io.IOException;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.appengine.repackaged.com.google.common.collect.ImmutableMap;
import com.google.gson.Gson;

import edu.berkeley.mvz.georef.Coordinates;
import edu.berkeley.mvz.georef.Datum;
import edu.berkeley.mvz.georef.DistanceUnit;
import edu.berkeley.mvz.georef.LatLng;
import edu.berkeley.mvz.georef.Localities;
import edu.berkeley.mvz.georef.Locality;

/**
 * Servelt for API requests.
 * 
 */
public class GeoCalcApi extends HttpServlet {

  private static final long serialVersionUID = -5043453429490500409L;

  @Override
  public void doGet(HttpServletRequest req, HttpServletResponse resp)
      throws IOException {

    // Extracts ll and e parameters and sends a 404 if error:
    double lat = 0, lon = 0, extent = 0;
    try {
      String ll = req.getParameter("ll");
      lat = Double.parseDouble(ll.split(",")[0]);
      lon = Double.parseDouble(ll.split(",")[1]);
      extent = Double.parseDouble(req.getParameter("e"));
    } catch (Exception e) {
      resp.sendError(404);
    }

    // Uses georef API to calculate PR:
    Coordinates c = new Coordinates.Builder(Coordinates.System.DD,
        Datum.WGS84_WORLD_GEODETIC_SYSTEM_1984, Coordinates.Source.GAZETTEER,
        DistanceUnit.METER, Coordinates.Precision.DD_ONE_THOUSANDTH).latitude(
        lat).longitude(lon).build();
    Locality l = Localities.namedPlaceOnly(c, extent);

    double error = l.getError(DistanceUnit.MILE);
    LatLng ll = l.getCoordinates().getPoint();
    String json = new Gson().toJson(ImmutableMap.of("point", ll, "radius",
        error));

    resp.setContentType("application/json");
    resp.getWriter().println(json);
  }
}