apache/maven · error · UnsupportedOperationException

Cannot change the artifactId for an attached artifact. It is

Error message

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

What it means

An AttachedArtifact shares the main artifact's groupId:artifactId:version; only type and classifier are its own. setArtifactId therefore always throws UnsupportedOperationException: the coordinate is derived from the parent and cannot be changed. The class is deprecated and internal; it exists to be created via attach flows, never mutated.

Source

Thrown at impl/maven-core/src/main/java/org/apache/maven/project/artifact/AttachedArtifact.java:75

        this.parent = parent;

        if (getId().equals(parent.getId())) {
            throw new InvalidArtifactRTException(
                    parent.getGroupId(),
                    parent.getArtifactId(),
                    parent.getVersion(),
                    parent.getType(),
                    "An attached artifact must have a different ID" + " than its corresponding main artifact.");
        }
    }

    public AttachedArtifact(Artifact parent, String type, ArtifactHandler artifactHandler) {
        this(parent, type, null, artifactHandler);
    }

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

    @Override
    public List<ArtifactVersion> getAvailableVersions() {
        return parent.getAvailableVersions();
    }

    @Override
    public void setAvailableVersions(List<ArtifactVersion> availableVersions) {
        throw new UnsupportedOperationException("Cannot change the version information for an attached artifact."
                + " It is derived from the main artifact.");
    }

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

View on GitHub (pinned to e4093d4e12)

Solutions

Adjust the artifactId at the source: set it on the project's main artifact before the attachment is created
If the artifact needs independent coordinates, create a standalone DefaultArtifact instead of an attached one
Guard mutators with an AttachedArtifact check before calling setters

Example fix

// before
attached.setArtifactId("new-id"); // UnsupportedOperationException

// after
Artifact standalone = new DefaultArtifact(groupId, "new-id", version, scope, type, classifier, handler);

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)) {
    throw new IllegalStateException("artifactId is derived from the main artifact; change the project instead");
}

Prevention

Treat artifacts from getAttachedArtifacts() as read-only views over the main artifact
Use MavenProjectHelper.attachArtifact to add artifacts instead of mutating existing attached ones

When it happens

Trigger: Calling setArtifactId(...) on an artifact obtained from MavenProject.getAttachedArtifacts() or created by MavenProjectHelper.attachArtifact, both of which yield AttachedArtifact instances.

Common situations: Generic artifact-processing code (publishers, reconcilers, copy utilities) that calls setters on every Artifact it sees; refactors of code that previously handled the mutable DefaultArtifact.

Related errors

AI-assisted analysis of apache/maven@e4093d4e12 (2026-08-21). Data as JSON: /api/errors/f84fd8841f319339. Report an issue: GitHub.