Context

Debezium supports custom converters to transform specific column types as they are read from a relational database. 

To offer the same level of flexibility in a native-friendly and declarative way, the Quarkus extension needs to expose an annotation-based mechanism for defining custom relational column converters.

Decision

Introduce a new annotation: @CustomConverter. This annotation allows CDI beans to declare a converter for a specific column typeName. The method must return a ConverterDefinition<SchemaBuilder> object, which describes how to map the source column to a target Kafka Connect schema and how to convert the value.

import io.debezium.engine.InsertEvent;
import jakarta.enterprise.context.ApplicationScoped;

@ApplicationScoped
class RawToStringConverter {

    @CustomConverter(filter=CustomFilter.class)
    public ConverterDefinition<SchemaBuilder> bind(RelationalColumn raw) { 
        return new ConverterDefinition<>(SchemaBuilder.string(), Object::toString);
    }
    
} 

The extension will scan for all such annotated methods at build time and register them during engine initialization.

Consequences

• Annotation scanning and mapping must occur during build time to ensure native compatibility.

• Only one converter may be registered per column typeName; conflicting converters must result in a build-time error.

• Reflection metadata for the involved classes must be included for native builds.

References:

Debezium Design Document: https://github.com/debezium/debezium-design-documents/pull/16