Call Google Maps API in a loop to geocode dozens of addresses and get "java.lang.String cannot be cast to net.sf.json.JSONObject"

The code below is what I use to call the Google Maps API to get the geocoded address for a raw address input.

This works fine if I do it for a handful of addresses at one time.

But if I run it in a loop on multiple addresses, I occasionally and unpredicatbly get this error:

java.lang.String cannot be cast to net.sf.json.JSONObject

It happens on a different input string each time I run the loop - so it doesn't seem to be related to the particular input data.

I might have expected to encounter a rate limitation in the Google Maps API but this error doesn't seem related to that?

Or is it?

package com.blogspot.unserializableone;

import java.io.ByteArrayOutputStream;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLEncoder;

import net.sf.json.JSONException;
import net.sf.json.JSONObject;

import org.apache.commons.io.IOUtils;

public class GCoder {
    private static final String URL = "http://maps.google.com/maps/geo?output=json";
    private static final String DEFAULT_KEY = "ABQIAAAAxPbpriJFATP1kV4Jfg7FrhTHx8S3jtCwO1hw0XE3N9WOac4cqRQ8_vMKB22No44yFau5GRY7TcCHZA";

    public static GAddress geocode(String address, String key) throws Exception {
        URL url = new URL(URL + "&q=" + URLEncoder.encode(address, "UTF-8") + "&key=" + key);
        URLConnection conn = url.openConnection();
        ByteArrayOutputStream output = new ByteArrayOutputStream(1024);
        IOUtils.copy(conn.getInputStream(), output);
        output.close();
        GAddress gaddr = new GAddress();
        JSONObject json = JSONObject.fromObject(output.toString());
        JSONObject placemark = (JSONObject) query(json, "Placemark[0]");
        final String commonId = "AddressDetails.Country.AdministrativeArea";
        gaddr.setFullAddress(query(placemark, "address").toString());
        gaddr.setZipCode(query(placemark,
                commonId + ".SubAdministrativeArea.Locality.PostalCode.PostalCodeNumber").toString());
        gaddr.setAddress(query(placemark,
                commonId + ".SubAdministrativeArea.Locality.Thoroughfare.ThoroughfareName")
                .toString());
        gaddr.setCity(query(placemark, commonId + ".SubAdministrativeArea.SubAdministrativeAreaName")
                .toString());
        gaddr.setState(query(placemark, commonId + ".AdministrativeAreaName").toString());
        gaddr.setLat(Double.parseDouble(query(placemark, "Point.coordinates[1]").toString()));
        gaddr.setLng(Double.parseDouble(query(placemark, "Point.coordinates[0]").toString()));
        return gaddr;
    }

    public static GAddress geocode(String address) throws Exception {
        return geocode(address, DEFAULT_KEY);
    } /* allow query for json nested objects, ie. Placemark[0].address */

    private static Object query(JSONObject jo, String query) {
        try {
            String[] keys = query.split("\\.");
            Object r = queryHelper(jo, keys[0]);
            for (int i = 1; i < keys.length; i++) {
                r = queryHelper(JSONObject.fromObject(r), keys[i]);
            }
            return r;
        } catch (JSONException e) {
            return "";
        }
    } /* help in query array objects: Placemark[0] */

    private static Object queryHelper(JSONObject jo, String query) {
        int openIndex = query.indexOf('[');
        int endIndex = query.indexOf(']');
        if (openIndex > 0) {
            String key = query.substring(0, openIndex);
            int index = Integer.parseInt(query.subst开发者_开发百科ring(openIndex + 1, endIndex));
            return jo.getJSONArray(key).get(index);
        }
        return jo.get(query);
    }

    public static void main(String[] args) throws Exception {
        System.out.println(GCoder.geocode("28 275, Mercedes, Buenos Aires, Argentina"));
        System.out.println(GCoder.geocode("94103"));
        System.out
                .println(GCoder.geocode("peña 2700 capital federal cdad. autonoma de buenos aires"));
        System.out.println(GCoder
                .geocode("2700 peña, capital federal, ciudad autonoma de buenos aires, argentina"));
    }
}

It looks like your error might be happening at this line --

    JSONObject placemark = (JSONObject) query(json, "Placemark[0]");

Looking at your query method, it also seems like you are swallowing the JSONException and returning an empty string which then cannot be cast to a JSONobject. So, its not an exception from the Google Maps API, but some exception in your code. I'd suggest printing stackTrace on that JSONException to investigate further.