Android: How to convert message pack binary data into readable JSON string?

[iraj-wisilica]

I already have JSON parsing module and works fine. Recently my back end team added support for message pack. So I am planning to convert the message pack data into JSON string so that I can keep the existing parsing logic.

Message Pack response from PHP back end.

The unpacker produces the following output.

Unpack: -17
Unpack: ��Response��Status��a
Unpack: 112
Unpack: 105
Unpack: 73
Unpack: 100
Unpack: 16
Unpack: -17
Unpack: �statusCode�N!�statusMessag
Unpack: 101
Unpack: -17
Unpack: �device get api is success�Da
Unpack: 116
Unpack: 97
Unpack: -17
Unpack: ��deviceCount�0�deviceDet
Unpack: 97
Unpack: 105
Unpack: 108
Unpack: 115
Unpack: -17
Unpack: ���message�No data found�

[iraj-wisilica]

Gentle reminder.

[komamitsu]

These examples might help https://github.com/msgpack/msgpack-java/tree/develop/msgpack-jackson#usage

I have no idea about what problem you're facing now.
You've already unpacked the MessagePack format byte array in Java that was packed by PHP and you're struggling to convert the Java object to JSON?

[iraj-wisilica]

Thanks for the reply. I am struggling to convert MessagePack byte array into JSON.

[komamitsu]

You can't convert MessagePack byte array into JSON directly. The following steps are needed.

1. Deserialize (Unpack) MessagePack byte array to a Java object
2. Serialize (Pack) the Java object to JSON format string

So I was interested in which step you're facing now.

[iraj-wisilica]

I am struck in #1. The POJO java object is dynamic so I can't map it to a static POJO class. I just want a JSON string from MessagePack byte array. Please provide me some code snippet.

[komamitsu]

If the schema of the object is dynamic, you'd better handle it as java.util.Map or org.msgpack.value.MapValue.
This is an example snippet although you may get the way from the usage I mentioned above

Ruby

irb(main):006:0> {name:'Foo Bar', age: 99, options: {aaa: 'AAAA', bbb: 'BBBB'}}.to_msgpack.unpack('C*')
=> [131, 164, 110, 97, 109, 101, 167, 70, 111, 111, 32, 66, 97, 114, 163, 97, 103, 101, 99, 167, 111, 112, 116, 105, 111, 110, 115, 130, 163, 97, 97, 97, 164, 65, 65, 65, 65, 163, 98, 98, 98, 164, 66, 66, 66, 66]

Java

        byte[] bytes = new byte[] {
                (byte)131, (byte)164, (byte)110, (byte)97, (byte)109, (byte)101, (byte)167, (byte)70,
                (byte)111, (byte)111, (byte)32, (byte)66, (byte)97, (byte)114, (byte)163, (byte)97,
                (byte)103, (byte)101, (byte)99, (byte)167, (byte)111, (byte)112, (byte)116, (byte)105,
                (byte)111, (byte)110, (byte)115, (byte)130, (byte)163, (byte)97, (byte)97, (byte)97,
                (byte)164, (byte)65, (byte)65, (byte)65, (byte)65, (byte)163, (byte)98, (byte)98,
                (byte)98, (byte)164, (byte)66, (byte)66, (byte)66, (byte)66};

        {
            ObjectMapper objectMapper = new ObjectMapper(new MessagePackFactory());
            Map<String, Object> map = objectMapper.readValue(bytes, new TypeReference<Map<String, Object>>() {});
            System.out.println(map.get("name"));
            System.out.println(map.get("age"));
            System.out.println(map.get("options"));
        }

        {
            Map<Value, Value> map = MessagePack.newDefaultUnpacker(bytes).unpackValue().asMapValue().map();
            System.out.println(map.get(ValueFactory.newString("name")));
            System.out.println(map.get(ValueFactory.newString("age")));
            System.out.println(map.get(ValueFactory.newString("options")));
        }

Foo Bar
99
{aaa=AAAA, bbb=BBBB}
Foo Bar
99
{"aaa":"AAAA","bbb":"BBBB"}

[iraj-wisilica]

Finally I fixed it using the below snippet. Thanks #komamitsu for your time and let me try your code snippet as well.

    MessageUnpacker unpacker = null;
    try {
        byte[] formattedBytes = Arrays.copyOfRange(responseBytes, 4, responseBytes.length); /* This line saved my life. I had to remove new line characters because my backend was always appending 4 junk new line bytes with the MessagePack byte array. */
        unpacker = new MessagePack.UnpackerConfig()
                .withStringDecoderBufferSize(16 * 1024) // If your data contains many large strings (the default is 8k)
                .newUnpacker(formattedBytes);

        ObjectMapper mapper = new ObjectMapper(new MessagePackFactory());
        try {
            JsonNode jsonNode = mapper.readTree(formattedBytes);
            String responseJson = jsonNode.toString();
            Log.i(TAG, "Response Json" + responseJson);
        } catch (IOException e) {
            Log.i(TAG, "Exception occurred" + e.getStackTrace());
        }
    } catch (Exception e) {
        e.printStackTrace();
    }

[komamitsu]

🎉
Yeah, using JsonNode would be smarter.

[iraj-wisilica]

Thank You.