Java – programmatically resolve Maven dependencies outside the plug-in – get the repository systemsession and repository system

Maybe this will be a bigger task than I thought at first, but no matter I try to load a maven project from a file and solve its dependencies I have two codes, but I lack some object references I need; Specifically, I need to get the instances of repository systemsession and repository system Any tips?

Note: I marked this issue with Maven plugin, but this is not a maven plugin I am happy to ask Maven 3 (think I already have...)

Here is my code so far:

Build Maven project:

public static MavenProject loadProject(File pomFile) throws Exception
{
    MavenProject ret = null;
    MavenXpp3Reader mavenReader = new MavenXpp3Reader();

    if (pomFile != null && pomFile.exists())
    {
        FileReader reader = null;

        try
            {
            reader = new FileReader(pomFile);
            Model model = mavenReader.read(reader);
            model.setPomFile(pomFile);

            ret = new MavenProject(model);
        }
        finally
        {
            // Close reader
        }
    }

    return ret;
}

Resolve dependencies:

public static List<Dependency> getArtifactsDependencies(MavenProject project,String dependencyType,String scope) throws Exception
{    
    DefaultArtifact pomArtifact = new DefaultArtifact(project.getId());

    RepositorySystemSession repoSession = null; // TODO
    RepositorySystem repoSystem = null; // TODO

    List<RemoteRepository> remoteRepos = project.getRemoteProjectRepositories();
    List<Dependency> ret = new ArrayList<Dependency>();

    Dependency dependency = new Dependency(pomArtifact,scope);

    CollectRequest collectRequest = new CollectRequest();
    collectRequest.setRoot(dependency);
    collectRequest.setRepositories(remoteRepos);

    DependencyNode node = repoSystem.collectDependencies(repoSession,collectRequest).getRoot();
    DependencyRequest projectDependencyRequest = new DependencyRequest(node,null);

    repoSystem.resolveDependencies(repoSession,projectDependencyRequest);

    PreorderNodeListGenerator nlg = new PreorderNodeListGenerator();
    node.accept(nlg);

    ret.addAll(nlg.getDependencies(true));

    return ret;
}

I know this may be an unusual requirement, maybe I should just discard what I'm doing and wrap it as a plug-in... But I just want to finish it now! Thank you in advance

Solution

Try jcabi aether, which is a wrapper from Apache aether from sonatype:

final File repo = this.session.getLocalRepository().getBasedir();
final Collection<Artifact> deps = new Aether(this.getProject(),repo).resolve(
  new DefaultArtifact("junit","junit-dep","","jar","4.10"),JavaScopes.RUNTIME
);

If you are an external Maven plugin:

final File repo = new File(System.getProperty("java.io.tmpdir"),"my-repo");
final MavenProject project = new MavenProject();
project.setRemoteArtifactRepositories(
  Arrays.asList(
    new RemoteRepository(
      "maven-central","default","http://repo1.maven.org/maven2/"
    )
  )
);
final Collection<Artifact> deps = new Aether(project,JavaScopes.RUNTIME
);