How to convert from JSONObject to MessagePack?

Question

I want to know if there is a way, in Java, to convert a JSONObject or a String with JSONObject format to MessagePack.

I tried to use MessagePackFactory but it doesn't seem to work. My JSONObject looks like :

{"value1":"value","object2":{"value3":"events","object1":{"name1":"name_1","boolean":true,"name3":"name3","name4":"name4","name5":"name6"},"object2":{},"object3":{"name7":"name7"},"value4":"value_4","value5":"value_5"},"value2":"subscribe","value3":"value3"}

Answer 1

I tried this in my project:

I've added a dependency in pom.xml

<dependency>
   <groupId>org.msgpack</groupId>
   <artifactId>msgpack-core</artifactId>
   <version>(version)</version>
</dependency>

after I've created a class like this:

import org.json.JSONObject;
import org.msgpack.core.MessageBufferPacker;
import org.msgpack.core.MessagePack;
import org.msgpack.core.MessageUnpacker;
import java.io.IOException;

public class JsonToMsgPack {

    public static void main(String[] args) throws IOException {
        // Sample JSON string
        String jsonString = "{\"name\":\"John\", \"age\":30, \"city\":\"New York\"}";

        // Convert JSON string to MessagePack bytes
        byte[] msgpackBytes = convertJsonToMsgPack(jsonString);

        // Just to demonstrate, convert MessagePack bytes back to JSON string
        String restoredJson = convertMsgPackToJson(msgpackBytes);

        System.out.println("Original JSON: " + jsonString);
        System.out.println("Restored JSON: " + restoredJson);
    }

    public static byte[] convertJsonToMsgPack(String jsonString) throws IOException {
        JSONObject jsonObject = new JSONObject(jsonString);
        MessageBufferPacker packer = MessagePack.newDefaultBufferPacker();
        packMap(jsonObject, packer);
        packer.close();
        return packer.toByteArray();
    }

    private static void packMap(JSONObject jsonObject, MessageBufferPacker packer) throws IOException {
        packer.packMapHeader(jsonObject.length());
        for (String key : jsonObject.keySet()) {
            packer.packString(key);
            Object value = jsonObject.get(key);
            if (value instanceof String) {
                packer.packString((String) value);
            } else if (value instanceof Integer) {
                packer.packInt((Integer) value);
            } else {
                // Extend as needed for other types
                throw new IllegalArgumentException("Unsupported type: " + value.getClass());
            }
        }
    }

    public static String convertMsgPackToJson(byte[] msgpackBytes) throws IOException {
        MessageUnpacker unpacker = MessagePack.newDefaultUnpacker(msgpackBytes);
        JSONObject jsonObject = unpackMap(unpacker);
        return jsonObject.toString();
    }

    private static JSONObject unpackMap(MessageUnpacker unpacker) throws IOException {
        int size = unpacker.unpackMapHeader();
        JSONObject jsonObject = new JSONObject();
        for (int i = 0; i < size; i++) {
            String key = unpacker.unpackString();
            switch (unpacker.getNextFormat()) {
                case STRING:
                    jsonObject.put(key, unpacker.unpackString());
                    break;
                case INT32:
                    jsonObject.put(key, unpacker.unpackInt());
                    break;
                // Extend as needed for other types
                default:
                    throw new IllegalArgumentException("Unsupported format: " + unpacker.getNextFormat());
            }
        }
        return jsonObject;
    }
}

For more information you can go here (documentation) or here (Medium article)