JSON.simple Example

JSON simple is a simple Java toolkit for JSON . You can use JSON simple to encode or
decode JSON text.
Features :
1 : Full compliance with JSON specification (RFC4627) and reliable.
2 : Provides multiple functionalities such as encode, decode/parse and escape
JSON text while keeping the library lightweight.
3 : Flexible, simple and easy to use by reusing Map and List interfaces.
4 : Supports streaming output of JSON text.
5 : Heap based parser.
6 : High performance.
7 : No dependency at all.

You need to download the JSON.simple library here and include it in java classpath.
1 : Write JSON to File
Write JSON data via JSONObject and JSONArray, and save it into a file named test.json

package json.simple; import java.io.FileWriter; import java.io.IOException; import org.json.simple.JSONArray; import org.json.simple.JSONObject; public class JsonSimpleTest { public static void main(String[] args) { JSONObject obj = new JSONObject(); obj.put("name", "tech24salt.blogspot.in"); obj.put("age", new Integer(34)); JSONArray list = new JSONArray(); list.add("Message 1"); list.add("Message 2"); list.add("Message 3"); list.add("Message 4"); list.add("Message 5"); obj.put("messages", list); try { FileWriter file = new FileWriter("d:\\test\\test.json"); file.write(obj.toJSONString()); file.flush(); file.close(); } catch (IOException e) { e.printStackTrace(); } System.out.print(obj); } } Output will be : {"age":34,"name":"tech24salt.blogspot.in","messages":["Message 1","Message 2","Message 3","Message 4","Message 5"]}
2 : Read JSON from File
Use JSONParser to read above generated JSON file test.json, and display each of the values.
package json.simple; import java.io.FileNotFoundException; import java.io.FileReader; import java.io.IOException; import java.util.Iterator; import org.json.simple.JSONArray; import org.json.simple.JSONObject; import org.json.simple.parser.JSONParser; import org.json.simple.parser.ParseException; public class JsonSimpleTestExample { public static void main(String[] args) { JSONParser parser = new JSONParser(); try { Object obj = parser.parse(new FileReader("d:\\test\\test.json")); JSONObject jsonObject = (JSONObject) obj; String name = (String) jsonObject.get("name"); System.out.println(name); long age = (Long) jsonObject.get("age"); System.out.println(age); // loop array JSONArray msg = (JSONArray) jsonObject.get("messages"); Iterator<String> iterator = msg.iterator(); while (iterator.hasNext()) { System.out.println(iterator.next()); } } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } catch (ParseException e) { e.printStackTrace(); } } } The Output are : tech24salt.blogspot.in 34 Message 1 Message 2 Message 3 Message 4 Message 5
Encode a JSON object - Streaming
//import org.json.simple.JSONObject; JSONObject obj=new JSONObject(); obj.put("name","foo"); obj.put("num",new Integer(100)); obj.put("balance",new Double(1000.21)); obj.put("is_vip",new Boolean(true)); obj.put("nickname",null); StringWriter out = new StringWriter(); obj.writeJSONString(out); String jsonText = out.toString(); System.out.print(jsonText); The Output : {"balance":1000.21,"num":100,"nickname":null,"is_vip":true,"name":"foo"}
Encode a JSON object - Using Map
//import java.util.LinkedHashMap; //import java.util.Map; //import org.json.simple.JSONValue; Map obj=new LinkedHashMap(); obj.put("name","foo"); obj.put("num",new Integer(100)); obj.put("balance",new Double(1000.21)); obj.put("is_vip",new Boolean(true)); obj.put("nickname",null); String jsonText = JSONValue.toJSONString(obj); System.out.print(jsonText); The Output : {"name":"foo","num":100,"balance":1000.21,"is_vip":true,"nickname":null}
Encode a JSON object - Using Map and streaming
//import java.util.LinkedHashMap; //import java.util.Map; //import org.json.simple.JSONValue; Map obj=new LinkedHashMap(); obj.put("name","foo"); obj.put("num",new Integer(100)); obj.put("balance",new Double(1000.21)); obj.put("is_vip",new Boolean(true)); obj.put("nickname",null); StringWriter out = new StringWriter(); JSONValue.writeJSONString(obj, out); String jsonText = out.toString(); System.out.print(jsonText); The Output : {"name":"foo","num":100,"balance":1000.21,"is_vip":true,"nickname":null}