How to get local repository location from Maven 3.0 plugin?

This one worked for me in Maven v3.6.0:

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

Use Aether as described in this blog post.

/**
 * The current repository/network configuration of Maven.
 *
 * @parameter default-value="${repositorySystemSession}"
 * @readonly
 */
private RepositorySystemSession repoSession;

now get the local Repo through RepositorySystemSession.getLocalRepository():

LocalRepository localRepo = repoSession.getLocalRepository();

LocalRepository has a getBasedir() method, which is probably what you want.

@Sean Patrick Floyd provided a solid answer.

This solution doesn't require the injection of the Properties into your instance fields.

@Override
public void execute() throws MojoExecutionException {
   MavenProject project=(MavenProject)getPluginContext().get("project");
   Set<Artifact> arts=project.getDependencyArtifacts();
   Set<String> localRepoSet = new HashSet<>();
   for (Artifact art : arts) {
        if (art.getScope().equals(Artifact.SCOPE_COMPILE)) {
            Path path = Paths.get(art.getFile().getAbsolutePath());

            String removal = art.getGroupId().replace(".", "/") + "/" + art.getArtifactId() + "/"
                    + art.getVersion();
            String localRepo = path.getParent().toAbsolutePath().toString().replace(removal, "");
            localRepoSet.add(localRepo);
        }
    }
}

You can get the possible locations of all of your direct dependencies.

Tested in Maven 3.X.X