JSON Parsing

JSON stands for JavaScript Object Notation.It is an independent data exchange format and is the best alternative for XML. This chapter explains how to parse the JSON file and extract necessary information from it.

Android provides four different classes to manipulate JSON data. These classes are JSONArray,JSONObject,JSONStringer and JSONTokenizer. The first step is to identify the fields in the JSON data in which you are interested in. For example, In the JSON given below we are interested in getting temperature only.

{

   “sys”:

   {

      “country”:”GB”,

      “sunrise”:1381107633,

      “sunset”:1381149604

   },

   “weather”:[

      {

         “id”:711,

         “main”:”Smoke”,

         “description”:”smoke”,

         “icon”:”50n”

      }

   ],

  “main”:

   {

      “temp”:304.15,

      “pressure”:1009,

   }

}

JSON – Elements

A JSON file consists of many components. Here is the table defining the components of an JSON file and their description −

JSON – Parsing

For parsing a JSON object, we will create an object of class JSONObject and specify a string containing JSON data to it. Its syntax is −

String in; 

JSONObject reader = new JSONObject(in);

The last step is to parse the JSON. A JSON file consists of different objects with different key/value pairs e.t.c. So JSONObject has a separate function for parsing each of the components of a JSON file. Its syntax is given below −

JSONObject sys  = reader.getJSONObject(“sys”);

country = sys.getString(“country”);

JSONObject main  = reader.getJSONObject(“main”);

temperature = main.getString(“temp”);

The method getJSONObject returns the JSON object. The method getString returns the string value of the specified key.

Apart from these methods , there are other methods provided by this class for better parsing JSON files. 

These methods are listed below −