Maven Invoker: IllegalStateException

Question

I have a multi-module Maven project (https://github.com/veniltonjr/msplearning)

One of my modules I need run programmatically the command from Maven build "clean install", but when I invoke the execution of these goals the following error occurs:

java.lang.IllegalStateException: Maven application directory was not specified, and ${maven.home} is not provided in the system properties. Please specify at least on of these.

In the Maven Invoker documentation is said that M2_HOME environment variable must exist.

Already have this variable set in my SO. This should not be enough to make the method invoke work? Follows the code snippet where I run the method in question:

Invoker invoker = new DefaultInvoker();
invoker.setLocalRepositoryDirectory(new File("C:\\git\\msplearning"));

InvocationRequest request = new DefaultInvocationRequest();
request.setGoals(Arrays.asList("clean", "install"));
InvocationResult result = invoker.execute(request); // Exception occours here...

Already, thanks!

EDITED (The Solution)

I had to set the POM and also set the Maven Home, which in my case is in the M3_HOME environment variable:

InvocationRequest request = new DefaultInvocationRequest();
request.setPomFile(new File("C:\\git\\msplearning\\pom.xml"));
request.setGoals(Collections.singletonList("verify"));

Invoker invoker = new DefaultInvoker();
invoker.setMavenHome(new File(System.getenv("M3_HOME")));
InvocationResult result = invoker.execute(request);

Thanks @RobertScholte and @khmarbaise!

Answer 1

Either set the request.pomFile or request.baseDirectory so the Invoker knows from which directory or file Apache Maven should be executed.

Answer 2

If you're running from a Maven-Surefire unit test then it's best to request that Surefire passes the maven.home system property on to its child processes. Per https://maven.apache.org/shared/maven-invoker/usage.html you can do this by adding the following config stanza:

<project>
  ...
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <version>2.12.4</version> <!-- see surefire-page for available versions -->
        <configuration>
          <systemPropertyVariables>
            <maven.home>${maven.home}</maven.home>
          </systemPropertyVariables>
        </configuration>
      </plugin>
    </plugins>
    ...
  </build>
  ...
</project>