@Override
    public <T> T mergeObject(T value, Schema<T> schema) throws IOException
    {

        if (value == null)
        {
            value = schema.newMessage();
        }

        MsgpackParser innerParser = new MsgpackParser(this.parser);
        MsgpackParser thisParser = use(innerParser);

        schema.mergeFrom(this, value);

        use(thisParser);

        return value;
    }
Use another parser in msgpack input
protostuff-msgpack/src/main/java/io/protostuff/MsgpackInput.java