Epic: Infer Java version/distribution from project files (.sdkmanrc, asdf, pom.xml, build.gradle)

[brunoborges]

Epic: Infer Java version and/or distribution from project files

Several open requests ask setup-java to read the Java version and/or distribution from an existing project/tooling file instead of (or in addition to) the java-version / distribution inputs. They share one design space — "resolve setup inputs from a file on disk" — so this epic tracks them together to keep behavior, precedence, and the java-version-file input consistent across formats.

Today's baseline

java-version-file already supports .java-version and reading java.version from pom.xml / build files in some cases. The items below extend the set of recognized files and add distribution detection.

Sub-requests

• Support extracting Java version from pom.xml and build.gradle via java-version-file #1034 — Extract Java version from pom.xml and build.gradle via java-version-file
• Specify distribution via java-version-file #646 — Specify the distribution via java-version-file (not just the version)
• Parse Java distribution from .sdkmanrc #971 — Parse Java distribution from .sdkmanrc · implemented by PR feat: Add distribution detection support to .sdkmanrc file #975
• Parse distribution from ASDF #738 — Parse distribution from ASDF (.tool-versions) · implemented by PR Infer distribution from asdf .tool-versions vendor prefix #1084 (merged)

Cross-cutting design questions

• Precedence when multiple sources are present (explicit input vs file vs multiple files).
• Whether a single java-version-file input auto-detects format, or distinct inputs per source.
• How distribution names in third-party files (SDKMAN!, asdf) map to setup-java distribution IDs.
• Behavior when a file specifies a distribution setup-java doesn't support.

Notes

This epic is for coordination/visibility — the individual issues remain open and can be implemented independently. PR #975 already covers the .sdkmanrc slice (#971).

[hupling]

for pom.xml

        <java.version>21</java.version>
        <maven.compiler.source>${java.version}</maven.compiler.source>
        <maven.compiler.target>${java.version}</maven.compiler.target>
        <maven.compiler.release>${java.version}</maven.compiler.release>

there you could add here.

https://github.com/actions/setup-java/blob/main/src/util.ts#L160

} else if (versionFileName == 'pom.xml') {
    javaVersionRegExp = /(?<java.version>(?<=(^|\s|-))(\d+\S*))(\s|$)/;
}

[brunoborges]

@hupling please see my comment in the actual issue