Maven "Fork failed ... Cannot run program javac" in CI

The compiler plugin is configured to fork a separate javac process, but the executable is not on PATH or at the configured executable path. The fork fails before any source is compiled.

What this error means

compile fails with "Fatal error compiling: Fork failed: java.io.IOException: Cannot run program \"javac\": error=2, No such file or directory" when <fork>true</fork> is set.

mvn output

[ERROR] Failed to execute goal
org.apache.maven.plugins:maven-compiler-plugin:3.13.0:compile (default-compile) on project app:
Fatal error compiling: Fork failed: java.io.IOException:
Cannot run program "javac": error=2, No such file or directory -> [Help 1]

Common causes

Forked compilation with javac not on PATH

With <fork>true</fork>, the plugin launches javac as a child process; if it is not on PATH (JRE, wrong JAVA_HOME), the fork fails.

A wrong <executable> path

A configured <executable> points at a javac that does not exist on the runner.

How to fix it

Provide a JDK so javac is on PATH

Install a JDK and let setup-java fix PATH and JAVA_HOME so the fork finds javac.

.github/workflows/ci.yml

- uses: actions/setup-java@v4
  with:
    distribution: temurin
    java-version: '21'

Point the compiler at the real javac

If you must set an explicit executable, use the JDK path that exists on the runner.

pom.xml

<configuration>
  <fork>true</fork>
  <executable>${env.JAVA_HOME}/bin/javac</executable>
</configuration>

How to prevent it

Run on a JDK with javac on PATH.
Avoid hard-coded <executable> paths that vary by runner.
Verify javac -version before forked compilation.