Java Checkstyle / Spotless

OpenMetadata enforces Java formatting via the Spotless Maven plugin. Every CI build runs mvn spotless:check and fails the PR if any file is not formatted. This skill keeps the fix on a single, consistent command so reviewers never have to ask for it manually again.

When to activate

• The user asks to "fix checkstyle", "fix Java formatting", "apply spotless", "run spotless", "format Java", or similar.
• CI posts a Java checkstyle failed / Fix Java checkstyle comment on a PR (the project's bot phrases the instruction as "Please run mvn spotless:apply in the root of your repository and commit the changes").
• After the assistant has finished authoring or editing any .java files — before opening a PR or pushing a commit that touches Java.

Arguments

• No arguments: run mvn spotless:apply at the repo root across all modules.
• -pl <module>: scope to a single Maven module (e.g. -pl openmetadata-service). Useful when only one module changed and you want a faster run.
• --check: run mvn spotless:check instead of apply. Use to confirm the tree is clean without touching files (e.g. to verify before push).

Process

Step 1: Run Spotless

From the repo root:

mvn spotless:apply                 # default — formats everything
# or
mvn -pl <module> spotless:apply    # scoped to one module
# or
mvn spotless:check                 # verify only, don't write

Spotless is fast (seconds, no compilation). If it fails with a plugin error (not a formatting diff), surface the error and stop — do not try to hand-edit formatting around the failure.

Step 2: Check what changed

git status --short
git diff --stat

Expect reformatting in .java files only. If Spotless touches pom.xml or other non-Java files, that's also fine — Spotless is configured for those too in this repo.

Step 3: Stage and commit (only if the user asked to commit)

Do NOT auto-commit. Report the changed file list to the user and let them decide whether to fold the formatting into the in-progress commit or make a separate "Fix Java checkstyle" commit. Follow the repo convention: the existing branch history already uses Fix Java checkstyle as the commit title for bot-triggered formatting-only commits.

Notes

• Spotless config lives in the root pom.xml (spotless-maven-plugin section). Do not redefine formatting rules inline in source files.
• If Spotless keeps rewriting a change the user just made, re-read the config — Spotless is the source of truth, not the IDE.
• The analogous UI command is yarn pretty (see the test-locally skill / CLAUDE.md for the UI lint flow); this skill is Java-only.