Improve GraphQL/DGS layer for Java 17 compatibility

[devin-ai-integration]

Summary

Code modernization of the GraphQL/DGS layer to eliminate problematic patterns and use modern Java APIs (Java 9–11), verified to compile cleanly on JDK 17.

Changes:

• Replace double-brace HashMap initialization with Map.of() in ArticleDatafetcher (3 sites) and CommentDatafetcher (1 site). Double-brace init creates anonymous inner class subclasses of HashMap on every call, which is wasteful and can cause subtle serialization/memory issues. Map.of() returns a compact, immutable map.
• Fix raw type cast in GraphQLCustomizeExceptionHandler.errorsToMap() — (List) → (List<String>) with a scoped @SuppressWarnings("unchecked").
• Replace containsKey()+put() with computeIfAbsent() in both getErrorsAsData and errorsToMap methods.
• Extract ConstraintViolationException to a local variable in onException() to eliminate repeated inline casting of handlerParameters.getException().

Review & Testing Checklist for Human

• Verify Map.of() immutability is safe: The original HashMap was mutable; Map.of() is unmodifiable. Confirm that no downstream DGS data fetcher or framework code mutates the localContext map. The child fetchers (ProfileDatafetcher.getAuthor(), CommentDatafetcher.articleComments()) appear to only call .get(), but runtime verification is important.
• Run the full test suite (./gradlew test) to validate no behavioral regressions — the Spotless formatter has a pre-existing incompatibility with JDK 17, so spotlessCheck will fail independently of these changes.
• Confirm computeIfAbsent equivalence in errorsToMap: The return type is Map<String, Object> but values are always ArrayList<String> — verify the unchecked cast path is safe.

Notes

• instanceof pattern matching (Java 16+) was considered but cannot be used because build.gradle sets sourceCompatibility = '11'. Upgrading sourceCompatibility/targetCompatibility to '17' (and the DGS codegen plugin to 6.x+) would unlock further modernization but is out of scope per task constraints.
• The DataFetcherExceptionHandler.onException() method is deprecated in graphql-java 17.x in favor of handleException() returning CompletableFuture. This is a pre-existing issue tied to the DGS 4.x / Spring Boot 2.6.x versions and not addressed here.
• javax.validation imports are correct for Spring Boot 2.6.x; migration to jakarta.validation would only be needed alongside a Spring Boot 3.x upgrade.

Link to Devin session: https://app.devin.ai/sessions/571f3f1add874782bfb8c4e91030b38e
Requested by: @shayanshafii

---

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 2 additional findings.