Phase 3: Migrate from Joda-Time to java.time API

[devin-ai-integration]

Phase 3: Migrate from Joda-Time to java.time API

Summary

This PR completes Phase 3 of the Java 17 upgrade by migrating from the legacy Joda-Time library (v2.10.13) to the modern java.time API. All DateTime usages have been replaced with Instant across 17 files, including:

• Domain models: Article, Comment
• DTOs: ArticleData, CommentData
• Infrastructure: MyBatis DateTimeHandler, Jackson serialization
• Services: ArticleQueryService, CommentQueryService
• GraphQL: ArticleDatafetcher, CommentDatafetcher
• Cursor pagination: DateTimeCursor
• Tests: All test files updated

Additionally, fixed a CI blocker by updating GitHub Actions workflow to use v4 instead of deprecated v2 actions.

Key Technical Changes:

• DateTime → Instant (UTC-based timestamps)
• new DateTime() → Instant.now()
• getMillis() → toEpochMilli()
• ISODateTimeFormat.dateTime().withZoneUTC().print() → DateTimeFormatter.ISO_INSTANT.format()
• MyBatis TypeHandler rewritten to use Timestamp.from() / timestamp.toInstant()
• Removed joda-time:2.10.13 dependency

CI Status: ✅ All checks passing (68 tests, build successful)

Review & Testing Checklist for Human

⚠️ CRITICAL - Serialization Format: The JSON timestamp format changed from Joda-Time's formatter to java.time's DateTimeFormatter.ISO_INSTANT. While both produce ISO 8601, verify:

• Compare API responses before/after migration to ensure timestamp format is character-for-character identical
• Check that existing API clients can still parse the timestamps correctly
• Test edge cases: null timestamps, very old dates, very new dates

⚠️ CRITICAL - Database Layer: The MyBatis DateTimeHandler was completely rewritten:

• Verify existing articles and comments in the database are still read correctly with their original timestamps
• Test creating new articles/comments and verify timestamps are persisted correctly
• Check that database timestamps are still UTC (run a query to inspect raw values)

⚠️ HIGH - Cursor Pagination: DateTimeCursor parsing logic changed:

• Test pagination with cursor values from before this migration (backwards compatibility)
• Test pagination end-to-end: fetch page 1, use cursor to fetch page 2, verify correct results
• Test edge cases: invalid cursors, null cursors, cursor at boundaries

Recommended End-to-End Test Plan:

1. Deploy to staging/test environment
2. Run existing integration tests against the deployed instance
3. Use actual API client (Postman/curl) to create articles and comments
4. Verify timestamps in responses match expected ISO 8601 format
5. Query database directly to verify persisted timestamp values
6. Test pagination flows with cursors
7. Monitor for any errors or unexpected behavior

Notes

Environment Issue - Spotless Formatting: There's an unresolved issue with the Google Java Format plugin (incompatible with Java 17). The code itself is correct and passes all tests, but may not follow the project's formatting standards. This is an environment configuration issue that needs to be addressed separately.

Regex Patterns: Verified that existing regex patterns (e.g., Article.toSlug()) are Java 17 compatible - no changes needed.

Session Info:

• Link to Devin run: https://app.devin.ai/sessions/cff7d281f5a94fd1974a77c7a7844926
• Requested by: Alex Peng (@alexjpeng)

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