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I am trying to write a parser from JSON data which I get from Google requesting coordinates of a city, which will create my specified object structure. For parsing, I've written a custom TypeAdapter.

It is my first time working with Gson, so probably my parsing method can be improved. Any suggestions?

JSON I receive:

    {
   "results" : [
      {
         "address_components" : [
            {
               "long_name" : "Los Angeles",
               "short_name" : "Los Angeles",
               "types" : [ "locality", "political" ]
            },
            {
               "long_name" : "Los Angeles County",
               "short_name" : "Los Angeles County",
               "types" : [ "administrative_area_level_2", "political" ]
            },
            {
               "long_name" : "California",
               "short_name" : "CA",
               "types" : [ "administrative_area_level_1", "political" ]
            },
            {
               "long_name" : "United States",
               "short_name" : "US",
               "types" : [ "country", "political" ]
            }
         ],
         "formatted_address" : "Los Angeles, CA, USA",
         "geometry" : {
            "bounds" : {
               "northeast" : {
                  "lat" : 34.3373061,
                  "lng" : -118.1552891
               },
               "southwest" : {
                  "lat" : 33.7036917,
                  "lng" : -118.6681759
               }
            },
            "location" : {
               "lat" : 34.0522342,
               "lng" : -118.2436849
            },
            "location_type" : "APPROXIMATE",
            "viewport" : {
               "northeast" : {
                  "lat" : 34.3373061,
                  "lng" : -118.1552891
               },
               "southwest" : {
                  "lat" : 33.7036917,
                  "lng" : -118.6681759
               }
            }
         },
         "partial_match" : true,
         "place_id" : "ChIJE9on3F3HwoAR9AhGJW_fL-I",
         "types" : [ "locality", "political" ]
      }
   ],
   "status" : "OK"
}

My POJO: only fields, without setters and getters to save space.

    public class GeoLocation {

    private String location_longName;
    private String location_shortName;
    private String country_longName;
    private String country_shortName;

    private String forrmatedAddress;

    private GeoCoordinates locationCordinates;
}

    public class GeoCoordinates {

    private Point northeastBounds;
    private Point southwestBounds;

    private Point northeastViewport;
    private Point southwestViewport;
    private Point location;
}

Custom TypeAdapter:

public class GeoLocationAdapter extends TypeAdapter<GeoLocation> {

    @Override
    public void write(JsonWriter jsonWriter, GeoLocation location) throws IOException {

    }

    @Override
    public GeoLocation read(JsonReader jsonReader) throws IOException {

        GeoLocation location = parsing(jsonReader);

        return location;
    }

    private GeoLocation parsing(JsonReader reader) throws IOException {
        GeoLocation location = new GeoLocation();
        GeoCoordinates coordinates = new GeoCoordinates();
        location.setLocationCordinates(coordinates);

        while (reader.peek() != JsonToken.END_DOCUMENT) {
            if (reader.peek() == JsonToken.NAME) {
                switch (reader.nextName()) {
                    case "results":
                    case "geometry":
                        break;
                    case "address_components":
                        reader.beginArray();
                        int i = 0;
                        String longName = null;
                        String shortName = null;
                        for (; ; ) {
                            if (reader.peek() == JsonToken.BEGIN_OBJECT) {
                                reader.beginObject();
                            }
                            if (reader.peek() == JsonToken.NAME) {
                                switch (reader.nextName()) {
                                    case "long_name":
                                        longName = reader.nextString();
                                        break;
                                    case "short_name":
                                        shortName = reader.nextString();
                                        break;
                                    case "types":
                                        while (reader.peek() != JsonToken.END_OBJECT) {
                                            reader.skipValue();
                                        }
                                        break;
                                }
                            }

                            if (reader.peek() == JsonToken.END_OBJECT) {
                                if (0 == i++) {
                                    location.setLocation_longName(longName);
                                    location.setLocation_shortName(shortName);
                                }
                                reader.endObject();
                            }

                            if (reader.peek() == JsonToken.END_ARRAY) {
                                location.setCountry_longName(longName);
                                location.setCountry_shortName(shortName);
                                reader.endArray();
                                break;
                            }
                        }
                        break;
                    case "formatted_address":
                        location.setForrmatedAddress(reader.nextString());
                        break;
                    case "bounds":
                        reader.beginObject();
                        for (; ; ) {
                            if (reader.peek() == JsonToken.NAME) {
                                switch (reader.nextName()) {
                                    case "northeast":
                                        reader.beginObject();
                                        location.getLocationCordinates().setNortheastBounds(parseCoordinates(reader));
                                        reader.endObject();
                                        break;
                                    case "southwest":
                                        reader.beginObject();
                                        location.getLocationCordinates().setSouthwestBounds(parseCoordinates(reader));
                                        reader.endObject();
                                        break;
                                }
                                if (reader.peek() == JsonToken.END_OBJECT) {
                                    reader.endObject();
                                    break;
                                }
                            }
                        }
                        break;
                    case "location":
                        reader.beginObject();
                        location.getLocationCordinates().setLocation(parseCoordinates(reader));
                        reader.endObject();
                        break;
                    case "viewport":
                        reader.beginObject();
                        for (; ; ) {
                            if (reader.peek() == JsonToken.NAME) {
                                switch (reader.nextName()) {
                                    case "northeast":
                                        reader.beginObject();
                                        location.getLocationCordinates().setNortheastViewport(parseCoordinates(reader));
                                        reader.endObject();
                                        break;
                                    case "southwest":
                                        reader.beginObject();
                                        location.getLocationCordinates().setSouthwestViewport(parseCoordinates(reader));
                                        reader.endObject();
                                        break;
                                }
                                if (reader.peek() == JsonToken.END_OBJECT) {
                                    reader.endObject();
                                    break;
                                }
                            }
                        }
                        break;
                    default:
                        reader.skipValue();
                        break;
                }
            }

            if (reader.peek() == JsonToken.BEGIN_OBJECT) {
                reader.beginObject();
            }

            if (reader.peek() == JsonToken.BEGIN_ARRAY) {
                reader.beginArray();
            }

            if (reader.peek() == JsonToken.END_OBJECT) {
                reader.endObject();
            }

            if (reader.peek() == JsonToken.END_ARRAY) {
                reader.endArray();
            }
        }
        return location;
    }

    private Point parseCoordinates(JsonReader reader) throws IOException {
        Double lat = null;
        Double lng = null;
        while (reader.peek() != JsonToken.END_OBJECT) {
            switch (reader.nextName()) {
                case "lat":
                    lat = reader.nextDouble();
                    break;
                case "lng":
                    lng = reader.nextDouble();
                    break;
            }
        }

        return new Point(lat, lng);
    }
}

Calling:

            GsonBuilder builder = new GsonBuilder();
        builder.registerTypeAdapter(GeoLocation.class, new GeoLocationAdapter());
        Gson gson = builder.create();

        GeoLocation locationObj = gson.fromJson(full, GeoLocation.class);

Please provide any improvements that can be made to code for ac-heaving better readability and performance. Also, can I leave the write method empty if I'm not planning to convert the result object back to JSON?

\$\endgroup\$
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  • \$\begingroup\$ Any reason not to use a JsonParser? The code would be much shorter. \$\endgroup\$
    – Tunaki
    Jan 24, 2016 at 21:56
  • \$\begingroup\$ was not aware of it, should try probably. Maybe you can explain a little how to implement it in my case? \$\endgroup\$
    – Edgar
    Jan 25, 2016 at 8:01

1 Answer 1

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You can parse the complete response easily using Google's Gson library:

class GeoResponse {
    List<Result> results;
    String status;

    static class Result {
        List<AddressComponent> address_components;
        String formatted_address;
        Geometry geometry;
        boolean partial_match;
        String place_id;
        List<String> types;

        static class AddressComponent {
            String long_name, short_name;
            List<String> types;
        }

        static class Geometry {
            Rect bounds;
            LatLng location;
            String location_type;
            Rect viewport;

            static class Rect {
                LatLng northeast, southwest;
            }

            static class LatLng {
                double lat, lng;
            }
        }
    }
}

...
import com.google.gson.Gson;

class GeoResponseParser {
    Gson gson = new Gson();
    GeoResponse parse(String responseStr) {
        return gson.fromJson(responseStr, GeoResponse.class);
    }
}
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  • \$\begingroup\$ yea it works, but I wanted to make different structure of object. \$\endgroup\$
    – Edgar
    Jan 30, 2016 at 9:01
  • \$\begingroup\$ @Edgar Then I would recommend letting Gson do the conversion to a Java object and then convert that object to one of the structure you want. \$\endgroup\$ Jan 30, 2016 at 14:35

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