Enable server checkstyle in CI and fix pre-existing violations

[krusche]

Summary

Enables Checkstyle in CI for the server and fixes the violations that had silently accumulated because it was never enforced.

Why

The Checkstyle config (server/config/checkstyle/checkstyle.xml, maxWarnings = 0) existed but nothing ran it in CI:

• server.Dockerfile builds with -x checkstyleMain -x checkstyleTest
• run_tests.yml only ran ./gradlew test (which doesn't trigger checkstyle)

As a result, ./gradlew checkstyleMain on develop currently fails with 3 violations (verified on a clean develop checkout).

Changes

Fix existing violations (all introduced by #1089, behavior-preserving):

• TopicRepository.searchTopics — two native-query lines exceeded the 200-char LineLength limit (Checkstyle counts tabs at width 8). Wrapped the OPEN/EXPIRED conditions onto continuation lines; the SQL is unchanged (newline = whitespace).
• TopicService.getPublishedFromResearchGroup — added the required public-method Javadoc (@param/@return, as JavadocMethod mandates).

Enforce going forward:

• Added a Run server checkstyle step (./gradlew checkstyleMain checkstyleTest) to run_tests.yml, before the test run so style issues fail fast.

Verification

• ./gradlew checkstyleMain checkstyleTest → BUILD SUCCESSFUL
• ./gradlew compileJava → succeeds
• CI runs the full test suite on this PR.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Tests

  • Added code style enforcement checks to the build pipeline to catch style violations early.

• Documentation

  • Improved method documentation with additional Javadoc comments.

• Style

  • Reformatted query code for improved readability.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: e9e212b8-2f31-4718-b1ba-bcefd5b5ba7d

📥 Commits

Reviewing files that changed from the base of the PR and between 4e054ad and 091a342.

📒 Files selected for processing (3)

• .github/workflows/run_tests.yml
• server/src/main/java/de/tum/cit/aet/thesis/repository/TopicRepository.java
• server/src/main/java/de/tum/cit/aet/thesis/service/TopicService.java

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Walkthrough

Adds checkstyleMain and checkstyleTest Gradle tasks as a pre-test CI step in the GitHub Actions workflow. Also reformats multi-line SQL conditions in TopicRepository's native query and adds a Javadoc block to TopicService.getPublishedFromResearchGroup — no logic changes.

Changes

Checkstyle CI enforcement and code hygiene

Layer / File(s)	Summary
Checkstyle CI step .github/workflows/run_tests.yml	Inserts a new step running checkstyleMain and checkstyleTest Gradle tasks in ./server before the existing test/coverage step.
SQL formatting and Javadoc server/src/main/java/de/tum/cit/aet/thesis/repository/TopicRepository.java, server/src/main/java/de/tum/cit/aet/thesis/service/TopicService.java	Reformats long AND conditions in the searchTopics native SQL query across multiple lines; adds a Javadoc comment to getPublishedFromResearchGroup. No logic changes.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main changes: enabling Checkstyle in CI and fixing pre-existing style violations across three files.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch chore/enable-checkstyle-ci

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