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I'm looking for a Java API which can be used to retreive Maven artifacts from a remote repository. I've found Eclipse Ather so far but it looks over complicated for my needs so i'm seeking for something more simple.
What i need is:
- I have to specify the location of the remote Maven repository
- I like to fetch an artifact based on it's groupId + artifactId + version
- The API have to provide the current remote version of the artifact (think about SNAPSHOT artifacts which are regularly built so they have a generated part in their versions)
- Return the location of the artifact, a HTTP URL is preferred (i'll fetch it on my own with eg. Apache HTTP Client)
- Optionally retreive the artifact's which are the dependants of the requested one.
jcabi-aether may help you (I'm a developer). It's a simple wrapper around Aether, that lets you find all transitive dependencies of a Maven artifact:
File repo = this.session.getLocalRepository().getBasedir();
Collection<Artifact> deps = new Aether(this.getProject(), repo).resolve(
new DefaultArtifact("junit", "junit-dep", "", "jar", "4.10"),
JavaScopes.RUNTIME
);
Thus, all you need to provide as an input is:
- Local repo location, as a directory name
- List of repote repositories (
MavenProject#getRemoteRepositories())
- Maven coordinates of the artifact
- Maven scope to look for
Absolute paths of every dependency found can be obtained as Artifact#getPath()
public List<Artifact> findDependencies(Artifact artifact) throws DependencyCollectionException {
CollectRequest collectRequest = new CollectRequest();
collectRequest.setRoot( new Dependency(artifact, "" ) );
collectRequest.addRepository(repository);
final MavenServiceLocator locator = new MavenServiceLocator();
locator.addService( RepositoryConnectorFactory.class, FileRepositoryConnectorFactory.class );
locator.addService( RepositoryConnectorFactory.class, WagonRepositoryConnectorFactory.class );
locator.setServices( WagonProvider.class, new WagonProvider() {
public Wagon lookup(String roleHint) throws Exception {
if (Arrays.asList("http", "https").contains(roleHint)) {
return new LightweightHttpWagon();
}
return null;
}
public void release(Wagon wagon) {
}
});
final RepositorySystem system = locator.getService(RepositorySystem.class);
MavenRepositorySystemSession session = new MavenRepositorySystemSession();
session.setLocalRepositoryManager( system.newLocalRepositoryManager(localRepository) );
session.setTransferListener( new LoggingTransferListener() );
session.setRepositoryListener( new LoggingRepositoryListener() );
final List<Artifact> artifacts = new ArrayList<Artifact>();
system.collectDependencies(session, collectRequest).getRoot().accept( new DependencyVisitor() {
public boolean visitEnter(DependencyNode dependencyNode) {
artifacts.add(dependencyNode.getDependency().getArtifact());
return true;
}
public boolean visitLeave(DependencyNode dependencyNode) {
return true;
}
});
return artifacts;
}
Aether jest actually pretty simple and elegant way of doing this. It's one of major enhancements in Maven 3 and many was looking for it. Look at this for some initial code to work with. I don't remember a method to get exact URL of the artifact, but other requirements are supported AFAIR.
Have you tried using Apache Ivy? It supports fetching maven dependencies.
The documentation for this use case is a little bit sparse, but I found some information on programmatic use of Ivy here.
