/java-checkstyle

name: java-checkstyle
description: Run `mvn spotless:apply` to fix Java checkstyle / formatting failures and verify the result. Invoke after authoring or modifying any `.java` files, or when CI reports a "Java checkstyle failed" or "Fix Java checkstyle" issue on a PR.
user-invocable: true
argument-hint: "[-pl <module>] [--check]"
allowed-tools:
  - Bash
  - Read
  - Grep
  - Glob

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 to this PR").

• After you have 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: Commit

Do not fold the reformat into an unrelated commit. If the user asked you to commit, follow their preference (fold into the in-progress commit, or make a separate one). Otherwise, when you are confident the change is a purely mechanical formatting reformat, you may commit it on its own as a `Fix Java checkstyle` commit — this matches the repo's existing history for bot-triggered formatting-only commits. If you are unsure whether the diff is purely mechanical, do NOT auto-commit: surface the changed-file list and let the user decide.

Notes

• Spotless config lives in the root `pom.xml` (`spotless-maven-plugin`

section) — `googleJavaFormat` + `removeUnusedImports`. Do not redefine formatting rules inline in source files.

• If Spotless keeps rewriting a change you just made, re-read the config —

Spotless is the source of truth, not the IDE.

• CI enforcement lives in `.github/workflows/java-checkstyle.yml`: the

`java-checkstyle` job runs `mvn spotless:apply` and fails (`git diff-files`) if the tree was not already formatted, posting the "Please run `mvn spotless:apply`" comment.

Out of scope

• UI / TypeScript formatting — use the `ui-checkstyle` skill

(ESLint + Prettier + organize-imports); this skill is Java-only.

• Python formatting — use `make py_format` (**ruff** lint-fix + format; see

`ingestion/Makefile`). *(Note: this is ruff, not black/isort/pycln.)*