Help parsing JSON in java

The two best options that I know of are:

• Jackson
• gson

Using them is a matter of calling one method of the mapper. But remember that since Java is statically-typed, you may have to create an object that has the required structure. (You don't have to, but it feels more natural)

From http://www.json.org, under the Java section:

• http://www.json.org/java/index.html
• http://json-lib.sourceforge.net/
• http://code.google.com/p/json-simple/
• http://code.google.com/p/jjson/

Pick your poison

With Jackson, following is the approach I'd take. Since the coordinates in the JSON come in two different formats -- sometimes an object, sometimes an array -- the solution is mildly complicated with necessary custom deserialization processing.

import java.io.File;
import java.io.IOException;
import java.math.BigDecimal;

import org.codehaus.jackson.JsonNode;
import org.codehaus.jackson.JsonParser;
import org.codehaus.jackson.JsonProcessingException;
import org.codehaus.jackson.ObjectCodec;
import org.codehaus.jackson.Version;
import org.codehaus.jackson.annotate.JsonAutoDetect.Visibility;
import org.codehaus.jackson.map.DeserializationContext;
import org.codehaus.jackson.map.JsonDeserializer;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.module.SimpleModule;
import org.codehaus.jackson.node.ArrayNode;

public class JacksonFoo
{
  public static void main(String[] args) throws Exception
  {
    ObjectMapper mapper = new ObjectMapper();
    mapper.setVisibilityChecker(mapper.getVisibilityChecker().withFieldVisibility(Visibility.ANY));
    mapper.registerModule(
      new SimpleModule("CoordinatesDeserializer", Version.unknownVersion())
        .addDeserializer(Coordinates.class, new CoordinatesDeserializer()));

    Result result = mapper.readValue(new File("input.json"), Result.class);
    System.out.println(mapper.writeValueAsString(result));
  }
}

class CoordinatesDeserializer extends JsonDeserializer<Coordinates>
{
  @Override
  public Coordinates deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException
  {
    ObjectCodec codec = jp.getCodec();
    JsonNode node = codec.readTree(jp);
    if (node.isObject())
    {
      ObjectMapper mapper = new ObjectMapper();
      mapper.setVisibilityChecker(mapper.getVisibilityChecker().withFieldVisibility(Visibility.ANY));
      return mapper.readValue(node, Coordinates.class);
    }
    // else it's an array
    ArrayNode array = (ArrayNode) node;
    Coordinates coordinates = new Coordinates();
    coordinates.latitude = codec.treeToValue(array.get(0), BigDecimal.class);
    coordinates.latitude = codec.treeToValue(array.get(1), BigDecimal.class);
    return coordinates;
  }
}

class Result
{
  Coordinates query;
  BigDecimal timestamp;
  Address address;
}

class Coordinates
{
  BigDecimal latitude;
  BigDecimal longitude;
}

class Address
{
  String type;
  Geometry geometry;
  AddressDetails properties;
}

class Geometry
{
  String type;
  Coordinates coordinates;
}

class AddressDetails
{
  String address;
  BigDecimal distance;
  String postcode;
  String city;
  String county;
  String province;
  String country;
}