creating Hashmap from a JSON String

Question

creating a hashmap from a json string in java?

I have json string like {"phonetype":"N95","cat":"WP"} and want to convert into a standard Hashmap.

How can i do it?

Solution 1

Parse the JSONObject and create HashMap

public static void jsonToMap(String t) throws JSONException {

        HashMap<String, String> map = new HashMap<String, String>();
        JSONObject jObject = new JSONObject(t);
        Iterator<?> keys = jObject.keys();

        while( keys.hasNext() ){
            String key = (String)keys.next();
            String value = jObject.getString(key); 
            map.put(key, value);

        }

        System.out.println("json : "+jObject);
        System.out.println("map : "+map);
    }

Tested output:

json : {"phonetype":"N95","cat":"WP"}
map : {cat=WP, phonetype=N95}

Solution 2

You can use Google's Gson library to convert json to Hashmap. Try below code

String jsonString = "Your JSON string";
HashMap<String,String> map = new Gson().fromJson(jsonString, new TypeToken<HashMap<String, String>>(){}.getType());

Solution 3

public class JsonMapExample {

    public static void main(String[] args) {
        String json = "{\"phonetype\":\"N95\",\"cat\":\"WP\"}";
        Map<String, String> map = new HashMap<String, String>();
        ObjectMapper mapper = new ObjectMapper();

        try {
            //convert JSON string to Map
            map = mapper.readValue(json, new TypeReference<HashMap<String, String>>() {});
            System.out.println(map);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Output:

{phonetype=N95, cat=WP}

You can see this link it's helpful http://www.mkyong.com/java/how-to-convert-java-map-to-from-json-jackson/

Solution 4

You could use Gson library

Type type = new TypeToken<HashMap<String, String>>() {}.getType();
new Gson().fromJson(jsonString, type);

Solution 5

This is simple operation 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(response)) ;

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