How to get ${basedir} value (or other properties) within the Mojo.execute()?

Question

I'm trying to get the value of the ${basedir} within a Mojo. I thought I could see that as a normal System property but

System.getProperty("basedir") 

returns null.

public void execute() throws MojoExecutionException, MojoFailureException {
    String baseDir = ???
}

Answer 1

This is done by injecting the MavenProject and invoking the getBaseDir() method, like this:

public class MyMojo extends AbstractMojo {

    @Parameter(defaultValue = "${project}", readonly = true, required = true)
    private MavenProject project;

    public void execute() throws MojoExecutionException, MojoFailureException {
        String baseDir = project.getBaseDir();
    }

}

The @Parameter is used to inject the value ${project}, which resolves to the current project being built from the Maven session.

Using annotations requires the following dependency on the Maven plugin:

<dependency>
  <groupId>org.apache.maven.plugin-tools</groupId>
  <artifactId>maven-plugin-annotations</artifactId>
  <version>3.5</version>
  <scope>provided</scope> <!-- annotations are needed only to build the plugin -->
</dependency>