fix: enable enum type metadata serialization with NON_FINAL_AND_ENUMS

[lukman48]

Description

Fixes issue #3306: RedisCache with GenericJacksonJsonRedisSerializer breaks when using enums.

Problem

When using GenericJacksonJsonRedisSerializer, enum values are always serialized without type metadata, even when DefaultTyping.NON_FINAL_AND_ENUMS is explicitly configured. This causes ClassCastException during deserialization.

Example

public enum Status {
    ACTIVE, INACTIVE
}

@Cacheable(cacheNames = "status")
public Status getStatus(String id) {
    return Status.ACTIVE;
}

When configured with:

GenericJacksonJsonRedisSerializer.create(b -> {
    b.customize(mb -> mb.activateDefaultTypingAsProperty(
        ptv,
        DefaultTyping.NON_FINAL_AND_ENUMS,
        "@class"
    ));
});

Expected: Enum cached with type metadata, deserializes correctly to Status enum
Actual: Throws ClassCastException: class java.lang.String cannot be cast to class Status

Root Cause

TypeResolverBuilder.useForType() unconditionally excludes enum types regardless of the DefaultTyping setting:

if (javaType.isEnumType() || ClassUtils.isPrimitiveOrWrapper(javaType.getRawClass())) {
    return false;  // Always excluded
}

This doesn't account for DefaultTyping.NON_FINAL_AND_ENUMS which explicitly requests enum type metadata.

Solution

1. Store DefaultTyping in TypeResolverBuilder - Add a field to preserve the typing configuration
2. Update useForType() logic - Check the DefaultTyping setting before excluding enums:
   • Return true for enums when DefaultTyping == NON_FINAL_AND_ENUMS
   • Return false for other settings (maintains backward compatibility)
3. Preserve existing behavior - Kotlin support and other logic unchanged

Implementation Details

Changes Made

File: GenericJacksonJsonRedisSerializer.java

1. Add defaultTyping field to TypeResolverBuilder
2. Initialize in all three constructors
3. Update useForType() to respect the configuration:

if (javaType.isEnumType()) {
    // Respect DefaultTyping.NON_FINAL_AND_ENUMS for enum types
    return defaultTyping == DefaultTyping.NON_FINAL_AND_ENUMS;
}

Test Coverage

Added three test cases in GenericJacksonJsonRedisSerializerUnitTests:

1. shouldSerializeEnumWithTypeMetadataWhenUsingNonFinalAndEnumsTyping

   • Verifies enums include type metadata when explicitly requested
   • Confirms correct deserialization to Enum type

2. shouldDeserializeEnumWithoutTypeMetadataUsingNonFinalTyping

   • Verifies backward compatibility
   • Confirms enums excluded with NON_FINAL

3. shouldHandleEnumWithUnsafeDefaultTyping_StillConvertsToStringDueToLegacyBehavior

   • Documents original bug (enums deserialize as strings with unsafe typing)
   • Shows our fix enables proper handling when configured correctly

Test Results: All 30 existing tests pass ✅

Backward Compatibility

✅ No breaking changes:

• Enums still excluded by default (NON_FINAL, OBJECT_AND_NON_FINAL, etc.)
• Only included when explicitly requested via NON_FINAL_AND_ENUMS
• No API changes
• All existing tests pass
• Kotlin support preserved

Validation

mvn clean test -Dtest=GenericJacksonJsonRedisSerializerUnitTests
# Results: Tests run: 30, Failures: 0, Errors: 0, Skipped: 0
# BUILD SUCCESS

Related

• Fixes RedisCache with GenericJacksonJsonRedisSerializer breaks when using enums #3306
• Aligns with Jackson's DefaultTyping.NON_FINAL_AND_ENUMS intent
• Enables caching of polymorphic types including enums

[lukman48]

✅ DCO Signature Updated

The commit has been amended with the required DCO (Developer Certificate of Origin) signature.

Changes Made:

• Added Signed-off-by: lukman48 <lukman_uki@yahoo.co.id> line
• Force-pushed updated commit to the branch
• DCO check: ACTION_REQUIRED → SUCCESS ✅

Commit Details:

• Old Hash: bbccb66
• New Hash: 0965640
• Signature: Verified and compliant

PR Status:

• ✅ DCO: SUCCESS
• ✅ Pull-Request check: SUCCESS
• ✅ All tests pass

Ready for maintainer review! 🚀

[mp911de]

We do have a design draft #3309 that addresses this issue. Serializers can be used in various contexts and so we want to provide an API that allows expressing sufficient control depending on the actual usage, hence closing this pull request as duplicate.