Custom type encoding (UUID)

Hi,

I’m trying to insert a UUID in a DB but the save call fails saying that there are no encoders supporting this type. Indeed DefaultCodecs does not have a UUIDCodec. I was not able to find a way to add a custom Codec though. Did I miss something? How would you recommend I can fix my problem?

For context, my DAO looks like this:

class Person {
  @Id
  Long id;
  UUID userUuid;
  String name;
}

[Tuegor]

Hi there, thanks for your suggestion.

The principle of R2DBC MySQL features’ provision is: “Compliant with R2DBC Specification, providing the same or compatible JDBC features.”

See https://github.com/r2dbc/r2dbc-spi/blob/master/r2dbc-spec/src/main/asciidoc/data-types.adoc , that means if MySQL does not support UUID, driver will be not provide UUID data type. (In fact, MySQL does not support UUID)

Good at evasions, huh? It that’s so, why does Spring Data JPA with a non-reactive driver support it no sweat? I’ll tell you why - because your statement is a lie. MySQL does support UUID, although it doesn’t have a separate data type for it like Postgres. That’s why it has the UUID() function, whose return value can be stored in a CHAR column. And if you apply UUID_TO_BIN() function to this value, you can store it compressed in a BINARY column. So say it straight - you are plain lazy to implement it, although it’s needed and two years have passed since this report.

[adrilo]

I managed to achieve what I want by registering custom Converters:

public class MySQLConfiguration extends AbstractR2dbcConfiguration {
    @Override
    protected List<Object> getCustomConverters() {
        return List.of(new UUIDToByteArrayConverter(), new ByteArrayToUUIDConverter());
    }
    ...
}

@WritingConverter
public class UUIDToByteArrayConverter implements Converter<UUID, byte[]> {
    @Override
    public byte[] convert(UUID source) {
        ByteBuffer bb = ByteBuffer.wrap(new byte[16]);
        bb.putLong(source.getMostSignificantBits());
        bb.putLong(source.getLeastSignificantBits());
        return bb.array();
    }
}

@ReadingConverter
public class ByteArrayToUUIDConverter implements Converter<byte[], UUID> {
    @Override
    public UUID convert(byte[] source) {
        return UUID.nameUUIDFromBytes(source);
    }
}

Still, given the large usage of UUIDs, it may be worth adding a codec for this type as part of the default set.