apache/maven · warning · InvalidArtifactRTException

The groupId cannot be empty.

Error message

The groupId cannot be empty.

What it means

After a download completes, DefaultWagonManager verifies the SHA-1 checksum. On the FIRST failure it assumes a transient server problem (the classic mirror bug: an HTTP-200 error page delivered instead of the file) and logs this warning, then re-downloads the artifact. On the second consecutive failure the repository's checksum policy (fail/warn/ignore) decides the outcome.

Source

Thrown at compat/maven-artifact/src/main/java/org/apache/maven/artifact/DefaultArtifact.java:167

        this.scope = scope;

        this.type = type;

        if (classifier == null) {
            classifier = artifactHandler.getClassifier();
        }

        this.classifier = classifier;

        this.optional = optional;

        validateIdentity();
    }

    private void validateIdentity() {
        if (empty(groupId)) {
            throw new InvalidArtifactRTException(
                    groupId, artifactId, getVersion(), type, "The groupId cannot be empty.");
        }

        if (empty(artifactId)) {
            throw new InvalidArtifactRTException(
                    groupId, artifactId, getVersion(), type, "The artifactId cannot be empty.");
        }

        if (empty(type)) {
            throw new InvalidArtifactRTException(groupId, artifactId, getVersion(), type, "The type cannot be empty.");
        }

        if ((empty(version)) && (versionRange == null)) {
            throw new InvalidArtifactRTException(
                    groupId, artifactId, getVersion(), type, "The version cannot be empty.");
        }
    }

View on GitHub (pinned to e4093d4e12)

Solutions

1. Let the automatic retry run; if the second attempt also fails, address the serving repository itself
2. Point mirrors at canonical Central (https://repo.maven.apache.org/maven2) instead of unmaintained intermediates
3. Delete the artifact from the local repository and rebuild with -U to force a clean fetch
4. Compare manually: curl the artifact and its .sha1 and check sha1sum to see which side is wrong

Example fix

<!-- before -->
<mirror>
  <id>flaky-mirror</id>
  <url>http://mymirror.example.com/maven2</url>
  <mirrorOf>central</mirrorOf>
</mirror>
<!-- after: canonical Central -->
<mirror>
  <id>central-fast</id>
  <url>https://repo.maven.apache.org/maven2</url>
  <mirrorOf>central</mirrorOf>
</mirror>

url=https://repo.maven.apache.org/maven2/path/to/artifact-1.0.jar
curl -fsS $url -o /tmp/a.jar && curl -fsS $url.sha1 -o /tmp/a.sha1
[ "$(sha1sum /tmp/a.jar | cut -d' ' -f1)" = "$(cat /tmp/a.sha1)" ] \
  || echo 'repo checksum broken; pick another mirror'

When it happens

Trigger: SHA-1 mismatch on the first verification: truncated or corrupted transfer, a mirror serving stale or wrong .sha1 files, or middleboxes rewriting response bodies.

Common situations: Third-party mirrors of Central lagging behind; flaky corporate proxies; interrupted network links during CI artifact fetches.

Related errors

• The type cannot be empty.
• artifactId can neither be null, empty nor blank
• version can neither be null, empty nor blank
• Unable to store local copy of metadata: {}
• Repository list contains duplicate entries. Each repository

AI-assisted analysis of apache/maven@e4093d4e12 (2026-08-21). Data as JSON: /api/errors/25b219cba436d4ff. Report an issue: GitHub.