GitHub Action and pre-commit¶

Both checks run the native binary, so they need no Java, Maven or Gradle. They work on Linux with glibc, on macOS and on Windows on x86-64. There is no native binary for musl-based Linux such as Alpine or for Windows on ARM.

Check pull requests and pushes¶

on:
  pull_request:
  push:
    branches: [main]

jobs:
  format:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v7

      - uses: openjavaformat/open-java-format-action@v2
        with:
          version: '2.98.0.3'
          mode: ${{ github.event_name == 'push' && 'all' || 'changed' }}

The action downloads the binary, lists the files that are not formatted and fails the job if there are any.

A workflow that still pins 2.98.0.1 stays on @v1: that version needs the --ojf flag, which @v2 does not pass.

On a pull request changed takes the file list from the pull request itself. On a push it compares the commits before and after, which needs that history in the checkout: either use mode: all for pushes, as above, or check out with fetch-depth: 0.

Fix what the check found¶

Run the formatter locally with the same version, then commit the result. See Command line for the download.

open-java-format --replace path/to/File.java

Exclude files¶

Both the action and the hook read an optional .open-java-format-exclude file in the repository root. Every line that is not empty and not a comment is a git pathspec, and a Java file that matches one is skipped.

# Standalone jbang scripts: the formatter would rewrite their //DEPS directives
samples/**

# Generated sources
**/build/generated/**

Git pre-commit hook¶

The same check can stop a commit before it reaches CI. Copy the hook script from the action's repository into your project:

curl -fsSL https://raw.githubusercontent.com/openjavaformat/open-java-format-action/v2/pre-commit -o .git/hooks/pre-commit
chmod +x .git/hooks/pre-commit

On its first run the hook downloads the native binary and caches it in ~/.cache/open-java-format. After that it checks only the staged .java files of each commit, and when one is not formatted it prints the command that fixes it.

To share the hook with the whole team, keep it in the repository instead:

mkdir -p .githooks
curl -fsSL https://raw.githubusercontent.com/openjavaformat/open-java-format-action/v2/pre-commit -o .githooks/pre-commit
chmod +x .githooks/pre-commit
git config core.hooksPath .githooks

The script pins its formatter version in FORMATTER_VERSION at the top. Keep it in step with the version your workflow passes to the action.