Parsing Json in Android with out using any external libraries

Question

I converted a map to a Json String using the code below

String msg = new JSONObject(map).toString();

How do I parse the above Json String to get the map back in Android with out using any external libraries?

Answer 1

If you have pairs of String/String you can easily restore it this way:

JSONObject obj = new JSONObject(msg); 
Iterator<String> keys = obj.keys();
HashMap<String, String> map = new HashMap<String, String>();
while(keys.hasNext()) {
   String key = keys.next();
   map.put(key, obj.optString(key));
}

Answer 2

You are asking how to parse but I don't see any JSON to parse in your question.

An example parsing method without any library looks like that:

JSONObject jo = new JSONObject(response);
JSONArray rootArray= jo.getJSONArray("jArray");
int rootArrayLength=rootArray.length();
for(int i=0;i<rootArrayLength;i++){
   int id=   rootArray.getJSONObject(i).getInt("value");
   // do same for others too and create an object
}
// create object and make a list

You can also check from my other answer to compare: Convert String to JsonArray

Answer 3

You can check my answer here for JSON Parsing:

https://stackoverflow.com/questions/21872643/about-json-parsing-exchange-data-with-rest-services/21872688#21872688

For completeness, please find the details below:

JSONObject is the key class for JSON Parsing. This class represent JSON data in key/value pair where values can be of any type: JSONObjects, JSONArrays, Strings, Booleans, Integers, Longs, Doubles

You create JSONObject as:

JSONObject jObject = new JSONObject(result);

where result is the response you obtain from your HTTPRequest.

Use this jObject to get different types using the specific names:

String:

String jsonString = jObject.getString("NAME");

Array:

JSONArray jsonArray = jObject.getJSONArray("NAME");

Eg. For parsing the places results I used following function, where JSON is something like:

  "results" : [
 {
 "geometry" : {
    "location" : {
       "lat" : 36.817729,
       "lng" : 10.18206
    }
 },
 "icon" : "http://maps.gstatic.com/mapfiles/place_api/icons/generic_business-71.png",
 "id" : "35a4f720fff88e2cfb94d64bfd7dbe95a8b4a632",
 "name" : "Banque Al-Baraka",
 "reference" : "CoQBcwAAAJbocdTKVg8I8CzgDdNtBQQaMsaghRlks-IWYl9eDNmFtftPHMgEfVeek_NHJZ2AN9JbiMda1WvREmoeIHBHsNdz9i7gtBaLM1xB93uhema_oswpqD-eRQ9b3fvTo4MhTOeIa7cRJ70BSEtDMONZqFyjqlGvL-5WsiwmqI1F3Vp_EhArWzyFuNrJdly2cHRBNxUJGhQjlcyHs-U2F0ILpN-ce-PHEesdqA",
 "types" : [ "bank", "finance", "establishment" ],
 "vicinity" : "88 P9, Tunis"
  },
  {
 "geometry" : {
    "location" : {
       "lat" : 36.861635,
       "lng" : 10.164628
    }
 },
 "icon" : "http://maps.gstatic.com/mapfiles/place_api/icons/generic_business-71.png",
 "id" : "da42093835270f902f64bc870154e6787fffbc7b",
 "name" : "Agence Ennasr",
 "reference" : "CnRwAAAAoh-XuMXghUKtv2UtHQJiRXB0ZugUnAkJIyP-vBd2YzTj5GdwIb5XhUS9x5-uY9_OwyQUdMmUeDHYm4KXHFNvOoj7diOOHAGBu-xCI4svIxcCwQ2w063mc2G3lohiScYMNpbKhwnCaggt0H1iknZY6xIQxDvNwVN0wWkVwO8zf_El5hoUwHgmgFflE31LDLj2_rr0uc1zvZM",
 "types" : [ "bank", "finance", "establishment" ],
 "vicinity" : "Avenue de Hédi Nouira, Ariana"
  },
]

Parsing JSON Array

public ArrayList<HashMap<String,String>> parseResult(JSONObject jsonObject) throws JSONException        {        
    JSONArray jsonArray = jsonObject.getJSONArray(Constants.RESULTS);
    ArrayList<HashMap<String, String>> placesList = new ArrayList<HashMap<String,String>>();
    for (int i = 0; i < jsonArray.length(); i++) {
        Object object = jsonArray.get(i);
        if (object instanceof JSONObject) {
            placesList.add(parsePlaceInfo((JSONObject) object));
       }
    }
    return placesList;
   }

Parsing simple JSON Object

private HashMap<String, String> parsePlaceInfo(JSONObject place) throws JSONException {
    String name = place.getString(Constants.NAME);
    String icon = place.getString(Constants.ICON);
    String vicinity = place.getString(Constants.VICINITY);
    JSONObject locationObject =    place.getJSONObject(Constants.GEOMETRY).getJSONObject(Constants.LOCATION);
    String lat = locationObject.getString(Constants.LAT);
    String lng = locationObject.getString(Constants.LNG);
    HashMap<String, String> placeDetails = new HashMap<String, String>();
    placeDetails.put(Constants.NAME, name);
    placeDetails.put(Constants.ICON, icon);
    placeDetails.put(Constants.VICINITY, vicinity);
    placeDetails.put(Constants.LAT, lat);
    placeDetails.put(Constants.LNG, lng);

    return placeDetails;  
}

Please note that this is not a complete code. I am providing you main details. Please let me know if you need any specific details regarding the code. Thanks!