Programatically getting an effective POM using Maven Resolver Provider

Question

What do I want to do?

Given a POM file on the local filesystem.
I want to programmatically obtain the effective POM of that POM file. Specifically I want to do the following:
- Resolve the POMs dependencies
- Ensure that all parent POMs are processed
- Obtain the list of dependencies of the fully resolved POM
- And so on...
I don't need to obtain transitive dependencies.

What works?

I'm using Maven Resolver Provider which sort of works. However I have to use a package private class org.apache.maven.repository.internal.DefaultModelResolver

Here a GitHub link to a sample Maven project that you can run: https://github.com/sahilm/maven-resolver-test

The example program does the following:

Downloads the latest spring boot POM from Maven Central.
Prints out it's direct dependencies (with parent deps included)

You can run the the program with: mvn exec:java -Dexec.mainClass="com.sahilm.maven_resolver_test.Test"

What I need help with?

I need help with understanding why I have to use a package private class to get stuff to work.
Is there another way to get the information I need?

I'm not sure what your question is, the above seems more like a series of statements. — Ardesco, Apr 09 '19 at 08:10
Do you mean the `DefaultModelResolver` is package? Because `ModelResolver` interface is public? — Marinos An, Apr 10 '19 at 09:55

score 4 · Answer 1 · answered Apr 10 '19 at 10:31

You can create (in your project) a public class under the package: org.apache.maven.repository.internal that extends the package-accessibility class. Just use a class name that is not possible to be used in the furutre by the vendor.

package org.apache.maven.repository.internal;
public class VisibleDefaultModelResolver extends DefaultModelResolver{

    public VisibleDefaultModelResolver(RepositorySystemSession session, RequestTrace trace, String context, ArtifactResolver resolver, VersionRangeResolver versionRangeResolver, RemoteRepositoryManager remoteRepositoryManager, List<RemoteRepository> repositories) {
        super(session, trace, context, resolver, versionRangeResolver, remoteRepositoryManager, repositories);
    }

}

Then your code becomes:

ModelResolver modelResolver = new VisibleDefaultModelResolver(session, requestTrace, "context", artifactResolver, versionRangeResolver, remoteRepositoryManager, repos);

That's interesting. Never knew you could do that! I still have a nagging feeling that there's a public API that I'm missing and that I have to combine the maven resolver provider with something else. This is helpful though and I'll accept your answer if I'm not able to find a public API. — Sahil Muthoo, Apr 10 '19 at 10:40

score 3 · Accepted Answer · answered Apr 10 '19 at 17:17

Maybe you can use ProjectModelResolver. Here's a code snippet,

    DefaultRepositorySystem repositorySystem =
            new DefaultRepositorySystem();
    repositorySystem.initService(locator);

    ModelResolver modelResolver =
            new ProjectModelResolver(session, requestTrace,
                    repositorySystem, remoteRepositoryManager, repos,
                    ProjectBuildingRequest.RepositoryMerging.POM_DOMINANT,
                    null);

I've included a working code here.

Awesome. This works. I skipped looking at this because I was unsure how to get a `ReactorModelPool`. Turns out I don't need to. Thanks! — Sahil Muthoo, Apr 10 '19 at 22:25

Programatically getting an effective POM using Maven Resolver Provider

What do I want to do?

What works?

What I need help with?

2 Answers2