public class Json {
  private ObjectNode objectNode;
  public Json() {}
  public Json(ObjectNode objectNode) {
    this.objectNode = objectNode;
  }
  public ObjectNode getObjectNode() {
    if (objectNode == null) {
      objectNode = JsonMapper.getMapper().createObjectNode();
    }
    return objectNode;
  }
  public void setObjectNode(ObjectNode objectNode) {
    this.objectNode = objectNode;
  }
  @Override
  public int hashCode() {
    return Objects.hashCode(this.objectNode);
  }
  @Override
  public boolean equals(Object obj) {
    if (obj.getClass() != Json.class) {
      return false;
    }
    return Objects.equals(this.objectNode, ((Json)obj).objectNode);
  }
}

public class JsonCodec implements Codec<Json>
{
    private final ObjectMapper objectMapper;
  private final BsonDocumentCodec bsonCodec;

    public JsonCodec(ObjectMapper objectMapper)
    {
        this.objectMapper = objectMapper;
    bsonCodec = new BsonDocumentCodec();
    }

  @Override
  public Json decode(BsonReader reader, DecoderContext decoderContext) {
    String str = "";
    try {
      BsonDocument doc = bsonCodec.decode(reader, decoderContext);
      str = doc.toJson();
      return new Json(objectMapper.readValue(str, ObjectNode.class));
    } catch (Exception ex) {
      throw new RuntimeException("Error mapping JSON from BSON reader : " + str, ex);
    }
  }

  @Override
  public void encode(BsonWriter writer, Json value, EncoderContext encoderContext) {
    String str = "";
    try {
      str = objectMapper.writeValueAsString(value.getObjectNode());
      BsonDocument doc = BsonDocument.parse(str);
      bsonCodec.encode(writer, doc, encoderContext);
    } catch (Exception ex) {
      throw new RuntimeException("Error encoding JSON to BSON writer : " + str, ex);
    }
  }

  @Override
  public Class<Json> getEncoderClass() {
    return Json.class;
  }
}