Convert JSON to Map

Question

What is the best way to convert a JSON code as this:

{ 
    \"data\" : 
    { 
        \"field1\" : \"value1\", 
        \"field2\" : \"value2\"
    }
}


        

Answer 1

I hope you were joking about writing your own parser. :-)

For such a simple mapping, most tools from http://json.org (section java) would work. For one of them (Jackson https://github.com/FasterXML/jackson-databind/#5-minute-tutorial-streaming-parser-generator), you'd do:

Map<String,Object> result =
        new ObjectMapper().readValue(JSON_SOURCE, HashMap.class);

(where JSON_SOURCE is a File, input stream, reader, or json content String)

Answer 2

I like google gson library.
When you don't know structure of json. You can use

JsonElement root = new JsonParser().parse(jsonString);

and then you can work with json. e.g. how to get "value1" from your gson:

String value1 = root.getAsJsonObject().get("data").getAsJsonObject().get("field1").getAsString();

Answer 3

JSON to Map always gonna be a string/object data type. i haved GSON lib from google.

works very well and JDK 1.5 is the min requirement.

Answer 4

Underscore-java library can convert json string to hash map. I am the maintainer of the project.

Code example:

import com.github.underscore.lodash.U;
import java.util.*;

public class Main {

    @SuppressWarnings("unchecked")
    public static void main(String[] args) {
        String json = "{"
            + "    \"data\" :"
            + "    {"
            + "        \"field1\" : \"value1\","
            + "        \"field2\" : \"value2\""
            + "    }"
            + "}";

       Map<String, Object> data = (Map) U.get((Map<String, Object>) U.fromJson(json), "data");
       System.out.println(data);

       // {field1=value1, field2=value2}
    }
}

Answer 5

Use JSON lib E.g. http://www.json.org/java/

// Assume you have a Map<String, String> in JSONObject jdata
@SuppressWarnings("unchecked")
Iterator<String> nameItr = jdata.keys();
Map<String, String> outMap = new HashMap<String, String>();
while(nameItr.hasNext()) {
    String name = nameItr.next();
    outMap.put(name, jdata.getString(name));

}