apache/maven · error · UnsupportedOperationException

Cannot change the repository information for an attached art

Error message

Cannot change the repository information for an attached artifact. It is derived from the main artifact.

What it means

The repository an artifact was resolved from is delegated to the main artifact: getRepository() returns the parent's repository, and setRepository throws UnsupportedOperationException on attached artifacts.

Source

Thrown at impl/maven-core/src/main/java/org/apache/maven/project/artifact/AttachedArtifact.java:125

    public void setDownloadUrl(String downloadUrl) {
        throw new UnsupportedOperationException("Cannot change the download information for an attached artifact."
                + " It is derived from the main artifact.");
    }

    @Override
    public void setGroupId(String groupId) {
        throw new UnsupportedOperationException(
                "Cannot change the groupId for an attached artifact." + " It is derived from the main artifact.");
    }

    @Override
    public ArtifactRepository getRepository() {
        return parent.getRepository();
    }

    @Override
    public void setRepository(ArtifactRepository repository) {
        throw new UnsupportedOperationException("Cannot change the repository information for an attached artifact."
                + " It is derived from the main artifact.");
    }

    @Override
    public String getScope() {
        return parent.getScope();
    }

    @Override
    public void setScope(String scope) {
        throw new UnsupportedOperationException("Cannot change the scoping information for an attached artifact."
                + " It is derived from the main artifact.");
    }

    @Override
    public String getVersion() {
        return parent.getVersion();
    }

View on GitHub (pinned to e4093d4e12)

Solutions

Stamp the repository on the main artifact before attaching
Track origin metadata in your own map keyed by artifact id instead of on the artifact
Skip attached artifacts when stamping repositories

Example fix

// before
attached.setRepository(localRepo);

// after
project.getArtifact().setRepository(localRepo);

Defensive patterns

Strategy: type-guard

Type guard

static boolean isAttachedArtifact(Artifact a) {
    return a instanceof org.apache.maven.project.artifact.AttachedArtifact;
}

Try / catch

if (isAttachedArtifact(artifact)) {
    project.getArtifact().setRepository(repo);
} else {
    artifact.setRepository(repo);
}

Prevention

Track artifact origin in your own metadata keyed by artifact id
Stamp repositories on the main artifact only

When it happens

Trigger: Calling setRepository(...) on an AttachedArtifact, usually resolver or caching code recording where each artifact came from.

Common situations: Resolver bridges or artifact caches stamping origin repositories onto all artifacts of a project; metadata collectors iterating getAttachedArtifacts().

Related errors

AI-assisted analysis of apache/maven@e4093d4e12 (2026-08-21). Data as JSON: /api/errors/00b04ae8e2c895e6. Report an issue: GitHub.