Problem

The current GitHub Actions workflow uses setup-java@v4 with cache: maven, which only performs exact cache key matching. When pom.xml files change (even slightly), the cache key changes and all Maven dependencies must be re-downloaded, leading to slower CI builds.

Solution

Replace the built-in caching with actions/cache@v4 to gain more control over cache fallback behavior:

• Primary key: ${{ runner.os }}-maven-${{ matrix.java }}-${{ hashFiles('**/pom.xml') }}
• Restore keys (fallback order):
  1. ${{ runner.os }}-maven-${{ matrix.java }}- - Any cache for same OS and Java version
  2. ${{ runner.os }}-maven- - Any Maven cache for same OS

Benefits

• ✅ Exact match: When pom.xml unchanged, uses exact cache
• ✅ Smart fallback: When pom.xml changed, reuses previous cache and only downloads new/changed dependencies
• ✅ Cross-version fallback: Can reuse caches across Java versions if needed
• ✅ Faster CI: Significantly reduces build times by avoiding full dependency re-downloads

Testing

This change maintains the same cache paths (~/.m2/repository) and is backward compatible with existing caches.

Pull Request opened by Augment Code with guidance from the PR author