How to convert jsonString to JSONObject in Java

Question

I have String variable called jsonString:

{"phonetype":"N95","cat":"WP"}

Now I want to convert it into JSON Object. I searched more on Google but didn't get any expected answers...

Answer 1

I like to use google-gson for this, and it's precisely because I don't need to work with JSONObject directly.

In that case I'd have a class that will correspond to the properties of your JSON Object

class Phone {
 public String phonetype;
 public String cat;
}


...
String jsonString = "{\"phonetype\":\"N95\",\"cat\":\"WP\"}";
Gson gson = new Gson();
Phone fooFromJson = gson.fromJson(jsonString, Phone.class);
...

However, I think your question is more like, How do I endup with an actual JSONObject object from a JSON String.

I was looking at the google-json api and couldn't find anything as straight forward as org.json's api which is probably what you want to be using if you're so strongly in need of using a barebones JSONObject.

http://www.json.org/javadoc/org/json/JSONObject.html

With org.json.JSONObject (another completely different API) If you want to do something like...

JSONObject jsonObject = new JSONObject("{\"phonetype\":\"N95\",\"cat\":\"WP\"}");
System.out.println(jsonObject.getString("phonetype"));

I think the beauty of google-gson is that you don't need to deal with JSONObject. You just grab json, pass the class to want to deserialize into, and your class attributes will be matched to the JSON, but then again, everyone has their own requirements, maybe you can't afford the luxury to have pre-mapped classes on the deserializing side because things might be too dynamic on the JSON Generating side. In that case just use json.org.

Answer 2

NOTE that GSON with deserializing an interface will result in exception like below.

"java.lang.RuntimeException: Unable to invoke no-args constructor for interface XXX. Register an InstanceCreator with Gson for this type may fix this problem."

While deserialize; GSON don't know which object has to be intantiated for that interface.

This is resolved somehow here.

However FlexJSON has this solution inherently. while serialize time it is adding class name as part of json like below.

{
    "HTTPStatus": "OK",
    "class": "com.XXX.YYY.HTTPViewResponse",
    "code": null,
    "outputContext": {
        "class": "com.XXX.YYY.ZZZ.OutputSuccessContext",
        "eligible": true
    }
}

So JSON will be cumber some; but you don't need write InstanceCreator which is required in GSON.

Answer 3

Better Go with more simpler way by using org.json lib. Just do a very simple approach as below:

JSONObject obj = new JSONObject();
obj.put("phonetype", "N95");
obj.put("cat", "WP");

Now obj is your converted JSONObject form of your respective String. This is in case if you have name-value pairs.

For a string you can directly pass to the constructor of JSONObject. If it'll be a valid json String, then okay otherwise it'll throw an exception.

Answer 4

There are various Java JSON serializers and deserializers linked from the JSON home page.

As of this writing, there are these 20:

• org.json
• org.json.me
• Jackson JSON Processor
• Json-lib
• JSON Tools
• json-simple
• Stringtree
• SOJO
• Restlet
• Jettison
• json-taglib
• XStream
• JsonMarshaller
• Flexjson
• JON tools
• google-gson
• Argo
• Pivot
• jsonij
• fastjson

...but of course the list can change.

Answer 5

To convert String into JSONObject you just need to pass the String instance into Constructor of JSONObject.

Eg:

JSONObject jsonObj = new JSONObject("your string");

Answer 6

No need to use any external library.

You can use this class instead :) (handles even lists , nested lists and json)

public class Utility {

    public static Map<String, Object> jsonToMap(Object json) throws JSONException {

        if(json instanceof JSONObject)
            return _jsonToMap_((JSONObject)json) ;

        else if (json instanceof String)
        {
            JSONObject jsonObject = new JSONObject((String)json) ;
            return _jsonToMap_(jsonObject) ;
        }
        return null ;
    }


   private static Map<String, Object> _jsonToMap_(JSONObject json) throws JSONException {
        Map<String, Object> retMap = new HashMap<String, Object>();

        if(json != JSONObject.NULL) {
            retMap = toMap(json);
        }
        return retMap;
    }


    private static Map<String, Object> toMap(JSONObject object) throws JSONException {
        Map<String, Object> map = new HashMap<String, Object>();

        Iterator<String> keysItr = object.keys();
        while(keysItr.hasNext()) {
            String key = keysItr.next();
            Object value = object.get(key);

            if(value instanceof JSONArray) {
                value = toList((JSONArray) value);
            }

            else if(value instanceof JSONObject) {
                value = toMap((JSONObject) value);
            }
            map.put(key, value);
        }
        return map;
    }


    public static List<Object> toList(JSONArray array) throws JSONException {
        List<Object> list = new ArrayList<Object>();
        for(int i = 0; i < array.length(); i++) {
            Object value = array.get(i);
            if(value instanceof JSONArray) {
                value = toList((JSONArray) value);
            }

            else if(value instanceof JSONObject) {
                value = toMap((JSONObject) value);
            }
            list.add(value);
        }
        return list;
    }
}

---

To convert your JSON string to hashmap use this :

HashMap<String, Object> hashMap = new HashMap<>(Utility.jsonToMap(