Help parsing JSON in java

Question

Would it be possible if someone could help me parse this json result. I have retrieved the result as a string

{"query":{"latitude":39.9889,"longitude":-82.8118},"timestamp":1310252291.861,"address":{"geometry":{"coordinates":[-82.81168367358264,39.9887910986731],"type":"Point"},"properties":{"address":"284 Macdougal Ln","distance":"0.02","postcode":"43004","city":"Columbus","county":"Franklin","province":"OH","country":"US"},"type":"Feature"}}

Answer 1

Jackson. Simple and intuitive to use. For me the best available. Start out with Simple Data Binding, it will throw everything it finds in Maps and Lists.

Like this:

ObjectMapper mapper = new ObjectMapper();
Map<String,Object> yourData = mapper.readValue(new File("yourdata.json"), Map.class);

That's all that's needed.

A good and quick introduction can be found here

And a full working example with your actual data:

import java.io.IOException;
import java.util.Map;
import org.codehaus.jackson.map.ObjectMapper;
public class Main {
 public static void main(String[] args) throws IOException {
 ObjectMapper mapper = new ObjectMapper();
 Map<?,?> rootAsMap = mapper.readValue(
 "{\"query\":{\"latitude\":39.9889,\"longitude\":-82.8118},\"timestamp\":1310252291.861,\"address\":{\"geometry\":{\"coordinates\":[-82.81168367358264,39.9887910986731],\"type\":\"Point\"},\"properties\":{\"address\":\"284 Macdougal Ln\",\"distance\":\"0.02\",\"postcode\":\"43004\",\"city\":\"Columbus\",\"county\":\"Franklin\",\"province\":\"OH\",\"country\":\"US\"},\"type\":\"Feature\"}}".getBytes(),
 Map.class);
 System.out.println(rootAsMap);
 Map query = (Map) rootAsMap.get("query");
 Map address = (Map) rootAsMap.get("address");
 Map addressProperties = (Map) address.get("properties");
 String county = (String) addressProperties.get("county");
 System.out.println("County is " + county);
 }
}

Now, this whole Map juggling also illustrates Bozho's point pretty well, using full binding (by creating a Java class that reflects the content of the JSON data) will work better in the end.

• Programmer Bruce: Jackson is the only JSON-to/from-Java library I've seen that will deserialize any Json object of arbitrary complexity to a Map<String, Object> in just one simple line. Note that the casts to Map and String would be unnecessary if a Map<String, Object> parameterized type reference were used with the call to readValue. TypeReference mapType = new TypeReference<Map<String, Object>>(){}; Map<String, Object> result = new ObjectMapper().readValue(new File("input.json"), mapType)
• Brandon Wilson: @fvu This example was the one I was looking for. It did what I need it to do. Thanks a lot. I run this through a for loop with a new string like the one above. So I need to escape the " on the new string as well?
• Brandon Wilson: Never mind I had a stupid moment when I saw this, LOL. I got everything working thanks a lot guys for all your help.

Answer 2

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)

• fvu: No you don't, see the link to Jackson simple databinding in my reply.
• Bozho: @fvu you don't have to, yeah, but it is better in most cases, imo
• Brandon Wilson: I guess I'm a little confused on the best route to take. It seems like every result is different. Im thinking I need clarification of what an object and arrays are what each result contains.
• fvu: @bozho the sheer simplicity of simple databinding makes it easy for people to get started, "upgrading" to full databinding is imo something that will come naturally.
• Brandon Wilson: @flu can you point to some good examples or tutorials? I just need a jump start. :)

Answer 3

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

• Programmer Bruce: This is a sampling of the worst JSON-to/from-Java libraries, right?

Answer 4

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;
}