Archives: JSON

Java – Convert Map to JSON

August 25, 2010 | By Prasanna Sherekar | Post comment

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

import java.lang.reflect.Type;
import java.util.HashMap;
import java.util.Map;

public class MapToJson {

    public static void main(String[] args) {
        Map < String, String > colours = new HashMap < String, String > ();
        colours.put("BLACK", "#000000");
        colours.put("RED", "#FF0000");
        colours.put("GREEN", "#008000");
        colours.put("BLUE", "#0000FF");
        colours.put("YELLOW", "#FFFF00");
        colours.put("WHITE", "#FFFFFF");

        //
        // Convert a Map into JSON string.
        //
        Gson gson = new Gson();
        String json = gson.toJson(colours);
        System.out.println("json = " + json);

        //
        // Convert JSON string back to Map.
        //
        Type type = new TypeToken < Map < String, String >> () {}.getType();
        Map < String, String > map = gson.fromJson(json, type);
        for (String key: map.keySet()) {
            System.out.println("map.get = " + map.get(key));
        }
    }

}

import com.google.gson.Gson;

import com.google.gson.reflect.TypeToken;

import java.lang.reflect.Type;

import java.util.HashMap;

import java.util.Map;

public class MapToJson {

public static void main(String[] args) {

Map < String, String > colours = new HashMap < String, String > ();

colours.put("BLACK", "#000000");

colours.put("RED", "#FF0000");

colours.put("GREEN", "#008000");

colours.put("BLUE", "#0000FF");

colours.put("YELLOW", "#FFFF00");

colours.put("WHITE", "#FFFFFF");

// Convert a Map into JSON string.

Gson gson = new Gson();

String json = gson.toJson(colours);

System.out.println("json = " + json);

// Convert JSON string back to Map.

Type type = new TypeToken < Map < String, String >> () {}.getType();

Map < String, String > map = gson.fromJson(json, type);

for (String key: map.keySet()) {

System.out.println("map.get = " + map.get(key));

}

Output:

json = {“WHITE”:”#FFFFFF”,”BLUE”:”#0000FF”,”YELLOW”:”#FFFF00″,”GREEN”:”#008000″,”BLACK”:”#000000″,”RED”:”#FF0000″}
map.get = #FFFFFF
map.get = #0000FF
map.get = #FFFF00
map.get = #008000
map.get = #000000
map.get = #FF0000

Java – Convert JSON to MongoDB Object

August 15, 2010 | By Prasanna Sherekar | Post comment

JSON Data to Convert:

{
‘name’ : ‘javac’,
‘age’ : 6
}

Conversion Code:

import java.net.UnknownHostException;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.DBObject;
import com.mongodb.Mongo;
import com.mongodb.MongoException;
import com.mongodb.util.JSON;

public class App {

    public static void main(String[] args) {
        try {

            Mongo mongo = new Mongo("localhost", 27017);
            DB db = mongo.getDB("yourdb");
            DBCollection collection = db.getCollection("dummyColl");

            // convert JSON to DBObject directly
            DBObject dbObject = (DBObject) JSON.parse("{'name':'javac', 'age':6}");

            collection.insert(dbObject);

            DBCursor cursorDoc = collection.find();
            while (cursorDoc.hasNext()) {
                System.out.println(cursorDoc.next());
            }

            System.out.println("Done");

        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (MongoException e) {
            e.printStackTrace();
        }
    }

}

import java.net.UnknownHostException;

import com.mongodb.DB;

import com.mongodb.DBCollection;

import com.mongodb.DBCursor;

import com.mongodb.DBObject;

import com.mongodb.Mongo;

import com.mongodb.MongoException;

import com.mongodb.util.JSON;

public class App {

public static void main(String[] args) {

try {

Mongo mongo = new Mongo("localhost", 27017);

DB db = mongo.getDB("yourdb");

DBCollection collection = db.getCollection("dummyColl");

// convert JSON to DBObject directly

DBObject dbObject = (DBObject) JSON.parse("{'name':'javac', 'age':6}");

collection.insert(dbObject);

DBCursor cursorDoc = collection.find();

while (cursorDoc.hasNext()) {

System.out.println(cursorDoc.next());

}

System.out.println("Done");

} catch (UnknownHostException e) {

e.printStackTrace();

} catch (MongoException e) {

e.printStackTrace();

}

Output:

{ “_id” : { “$oid” : “4dc9ebb5237f275c2fe4959f”} , “name” : “javac” , “age” : 6}
Done

Java – Read JSON Data Simple Example

May 30, 2010 | By Prasanna Sherekar | Post comment

In below example, it uses JSONParser to read and display JSON data from a file named “test.json“ using JSON.simple, a simple Java library for JSON processing.

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 JsonSimpleExample {
    public static void main(String[] args) {

        JSONParser parser = new JSONParser();

        try {

            Object obj = parser.parse(new FileReader("c:\\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();
        }

    }

}

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 JsonSimpleExample {

public static void main(String[] args) {

JSONParser parser = new JSONParser();

try {

Object obj = parser.parse(new FileReader("c:\\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();

}

Output:

prasanna
25
msg 1
msg 2
msg 3