fix(dynamodb-enhanced): Fix NPE in EnhancedType for null and wildcard types

[abhu85]

Summary

This PR fixes NullPointerException bugs in the DynamoDB Enhanced Client's EnhancedType class when dealing with wildcard types like List<?>.

Issue #5890: EnhancedType.hashCode(), equals(), and toString() throw NPE when dealing with wildcard types where rawClass is null.

Root Cause

For wildcard types (e.g., List<?>), EnhancedType stores rawClass = null. The following methods called methods on rawClass without null checks:

• hashCode() called rawClass.hashCode()
• equals() called rawClass.equals()
• innerToString() called rawClass.getTypeName()

Changes

• EnhancedType.java: Add null checks for rawClass in hashCode(), equals(), and innerToString() methods
• EnhancedTypeTest.java: Add 3 tests for wildcard type handling in hashCode(), equals(), and toString()

Test Plan

• All 26 EnhancedTypeTest tests pass (including 3 new tests)
• Tests verify: wildcard hashCode, wildcard equality, wildcard toString

Test Commands

```bash
./mvnw test -pl services-custom/dynamodb-enhanced -Dtest=EnhancedTypeTest

Tests run: 26, Failures: 0, Errors: 0, Skipped: 0

```

Fixes #5890

---

Note: The ConverterUtils fix for #6639 has been moved to a separate PR: #6761

[bhoradc]

Hi @abhu85

Thanks for the PR! If you don't mind, could you remove the ConverterUtils changes (#6639) from this PR and submit those as a separate PR?

Also on the EnhancedType wildcard issue, we noticed that toString() has the same NPE when processing wildcard type parameters. Would you mind including a fix for that as well in this PR?

Thanks again for the contribution!

Regards,
Chaitanya

[abhu85]

Hi @bhoradc,

Thanks for the feedback! I've addressed both requests:

1. Split the PR: Removed the ConverterUtils changes from this PR and submitted them separately as fix(dynamodb-enhanced): Fix NPE in ConverterUtils for null input #6761.

2. Added toString() fix: Added null check in innerToString() for wildcard types, plus a test that verifies:

   • wildcardParam.toString() returns "EnhancedType(?)"
   • listWithWildcard.toString() returns "EnhancedType(java.util.List<?>)"

Summary of changes in this PR now:

• EnhancedType.java: Null checks in hashCode(), equals(), and toString()/innerToString() for wildcard types
• EnhancedTypeTest.java: 3 tests for wildcard handling (hashCode, equals, toString)
• Updated changelog to reflect EnhancedType-only changes

Please let me know if any further changes are needed!

[bhoradc]

@abhu85 - Thanks for the quick updates.

One more thing - could you update the PR description to reflect the current scope? It still references the ConverterUtils changes in all sections. Just to keep it clean and ensure we don't accidently close that issue once this merges. Thanks.

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[abhu85]

Hi @bhoradc,

Apologies for the delay! I've updated the PR description to reflect the current scope - it now only references the EnhancedType changes for #5890.

The ConverterUtils changes for #6639 remain in the separate PR #6761.

Please let me know if there's anything else needed!

[abhu85]

Thanks for the feedback @alextwoods! I've added a test case wildcardType_equals_notEqualToNonWildcard that covers the wildcard != non-wildcard comparison, testing both directions:

@Test
public void wildcardType_equals_notEqualToNonWildcard() {
    // A wildcard type (rawClass=null) should not be equal to a non-wildcard type (rawClass!=null)
    EnhancedType<List<?>> listWithWildcard = new EnhancedType<List<?>>(){};
    EnhancedType<?> wildcardType = listWithWildcard.rawClassParameters().get(0);
    EnhancedType<String> nonWildcardType = EnhancedType.of(String.class);

    // Wildcard vs non-wildcard should not be equal (tests both comparison directions)
    assertThat(wildcardType).isNotEqualTo(nonWildcardType);
    assertThat(nonWildcardType).isNotEqualTo(wildcardType);
}

This exercises the ternary logic in equals() line 572 when this.rawClass == null but other.rawClass != null, and vice versa.

[abhu85]

@alextwoods The CI is failing on the API surface area check because this PR modifies public methods in EnhancedType.java (equals(), hashCode(), toString()).

Could you please add one of the following labels after review?

• api-surface-area-reviewed - if the API changes are approved
• no-api-surface-area-change - if this is considered a false positive (the behavioral contract is unchanged, just null-safety improvements)

Thanks!

[sonarqubecloud]

Quality Gate passed

Issues
9 New issues
0 Accepted issues

Measures
0 Security Hotspots
92.9% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[alextwoods]

@abhu85 - Added the no-api-surface-area-change label since this doesn't have API changes. CI looks good other than that.