Greg Harris created KAFKA-14671:
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             Summary: Refactor PredicatedTransformation to not implement 
Transformation
                 Key: KAFKA-14671
                 URL: https://issues.apache.org/jira/browse/KAFKA-14671
             Project: Kafka
          Issue Type: Task
          Components: KafkaConnect
    Affects Versions: 3.5.0
            Reporter: Greg Harris
            Assignee: Greg Harris


The PredicatedTransformation 
[https://github.com/apache/kafka/blob/trunk/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/PredicatedTransformation.java]
 
is an instance of Transformation, a plugin class.
This allows both a PredicatedTransformation and a base Transformation to exist 
in the same list inside of the TransformationChain.

However, the PredicatedTransformation is not a compliant general-purpose 
Transformation, and has a number of non-standard behaviors:
1. The PredicatedTransformation is hidden from the REST API plugin listings
2. PredicatedTransformation::config and ::configure throw an exception, as they 
are not called under normal circumstances
3. The PredicatedTransformation has no default constructor, and would throw an 
exception if loaded via the standard plugin initialization logic.
4. The TransformationChain calls `.getClass()` on the PredicatedTransformation, 
which returns the PredicatedTransformation class itself, and not the wrapped 
transformation class.

The PredicatedTransformation is a reasonable abstraction to compose a predicate 
and transformation, but it can do so without subclassing Transformation, and 
incurring the above pitfalls.



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