Deprecate `*ConverterOverride` classes in favor of `R2dbcCustomConversionsConfiguration` converter filters

[magiccrafter]

Hi team,

I'm struggling to understand the reasoning for having the converter overrides from the code snippet below:

from: R2dbcConverters

	/**
	 * @return A list of the registered converters to enforce JSR-310 type usage.
	 * @see CustomConversions#DEFAULT_CONVERTERS
	 * @see Jsr310Converters
	 */
	public static Collection<Object> getOverrideConvertersToRegister() {

		List<Object> converters = new ArrayList<>();

		converters.add(LocalDateConverterOverride.INSTANCE);
		converters.add(LocalDateTimeConverterOverride.INSTANCE);
		converters.add(LocalTimeConverterOverride.INSTANCE);

		return converters;
	}

The problem I face is that because of the overrides from the snippet above any custom converters specified for a custom R2dbcDialect implementation is being overridden and respectively ignored.

For example, in the following custom R2dbcDialect class the converters are ignored and the *Override's one take precedence:

public class CustomR2dbcDialect extends AbstractDialect implements R2dbcDialect {
   ...
    @Override
    public Collection<? extends Class<?>> getSimpleTypes() {
      return Arrays.asList(
        XTimestamp.class,
        XDate.class);
    }
  
    @Override
    public Collection<Object> getConverters() {
      return Arrays.asList(
        new LocalDateToXDateConverter(),
        new XDateToLocalDateConverter(),
        new LocalDateTimeToXTimestampConverter(),
        new XTimestampToLocalDateTimeConverter());
    }
    ...
  }

What is the purpose of the *ConverterOverride classes and does it make sense to remove the converter overrides?

[magiccrafter]

To workaround the above problem one could possibly define a R2dbcCustomConversions bean with the converters that are being overrriden:

@Bean
@ConditionalOnMissingBean
public R2dbcCustomConversions customConversions() {
    return R2dbcCustomConversions.of(
        new XR2dbcDialect(),
        Arrays.asList(
            new LocalDateToXDateConverter(),
            new XDateToLocalDateConverter(),
            new LocalDateTimeToXTimestampConverter(),
            new XTimestampToLocalDateTimeConverter()
        )
    );
}

This wrapped in an Autoconfigure class provided by the client library seems like a proper hack 🤔
It would be great if there is a more elegant way to avoid the custom *Override.java clases.

[mp911de]

…ConverterOverride classes are in place to apply identity conversion. Spring Data Commons auto-registers by default converters that convert JSR-310 temporal types to java.util.Date which isn't desired in a R2DBC arrangement. However, with JDBC, MongoDB, and Cassandra LocalDate to java.util.Date makes sense.

The R2DBC converter configuration deliberately filters converters that want to convert from JSR-310 temporal types into java.util.Date.

Creating custom conversions via R2dbcCustomConversions.of(…) is the proper way to customize converters as the custom conversions object applies typically per Spring Data module and you want to properly isolate converters.

I think the underlying issue should be solved in order to make your conversion work. That is, that the underlying driver doesn't support JSR-310 temporal types. While at it, we should be able to remove our …ConverterOverride types as we have the aforementioned converter filter in place anyway.