GoogleContainerTools/jib · error · MojoExecutionException

Skaffold sync is currently only available for 'jar' style Ji

Error message

Skaffold sync is currently only available for 'jar' style Jib projects, but the packaging of ${getProject().getArtifactId()} is '${getProject().getPackaging()}'

What it means

SyncMapMojo (skaffold-sync goal) generates the sync map Skaffold uses for hot-reloading files into a running container. Sync only works for jar-packaged projects, so the mojo throws this MojoExecutionException when the project's <packaging> is anything other than 'jar' (e.g. war, pom, custom). This is a configuration incompatibility, not a bug.

Source

Thrown at jib-maven-plugin/src/main/java/com/google/cloud/tools/jib/maven/skaffold/SyncMapMojo.java:56

    name = SyncMapMojo.GOAL_NAME,
    requiresDependencyCollection = ResolutionScope.COMPILE_PLUS_RUNTIME)
public class SyncMapMojo extends JibPluginConfiguration {

  @VisibleForTesting static final String GOAL_NAME = "_skaffold-sync-map";

  @Parameter SkaffoldConfiguration skaffold = new SkaffoldConfiguration();

  @Override
  public void execute() throws MojoExecutionException {
    checkJibVersion();
    if (MojoCommon.shouldSkipJibExecution(this)) {
      return;
    }

    // TODO: move these shared checks with SyncMapTask into plugins-common
    // add check that means this is only for jars
    if (!"jar".equals(getProject().getPackaging())) {
      throw new MojoExecutionException(
          "Skaffold sync is currently only available for 'jar' style Jib projects, but the packaging of "
              + getProject().getArtifactId()
              + " is '"
              + getProject().getPackaging()
              + "'");
    }
    // add check for exploded containerization
    try {
      if (!ContainerizingMode.EXPLODED.equals(ContainerizingMode.from(getContainerizingMode()))) {
        throw new MojoExecutionException(
            "Skaffold sync is currently only available for Jib projects in 'exploded' containerizing mode, but the containerizing mode of "
                + getProject().getArtifactId()
                + " is '"
                + getContainerizingMode()
                + "'");
      }
    } catch (InvalidContainerizingModeException ex) {
      throw new MojoExecutionException("Invalid containerizing mode", ex);

View on GitHub (pinned to fb949e2676)

Solutions

1. Change the module packaging to <packaging>jar</packaging> if a jar is actually intended.
2. Disable Skaffold sync for that module (remove sync config or skip the goal) since only jar projects are supported.
3. For WAR projects, use Jib's WAR support for building but rely on rebuilds instead of sync.
4. Split jar-producing code out of the war/pom module if sync is essential.

Example fix

// before
<packaging>war</packaging>
// after
<packaging>jar</packaging>

boolean syncSupported = "jar".equals(project.getPackaging());
if (!syncSupported) throw new IllegalStateException("Skaffold sync requires <packaging>jar</packaging>");

try { ... } catch (MojoExecutionException e) { if (e.getMessage().contains("only available for 'jar' style")) { /* disable sync for this module */ } }

When it happens

Trigger: Running the skaffold-sync goal (or Skaffold dev with sync enabled) on a Maven project whose <packaging> is not 'jar'.

Common situations: Enabling Skaffold file sync on a WAR-based webapp or a pom aggregator module; applying a generic Skaffold config across mixed-packaging multi-module projects.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Skaffold sync is currently only available for Jib projects i
• Could not determine Jib plugin version
• Jib plugin version is %s but is required to be %s
• _skaffold-fail-if-jib-out-of-date requires jib.requiredVersi
• Failed to resolve dependencies

AI-assisted analysis of GoogleContainerTools/jib@fb949e2676 (2026-09-06). Data as JSON: /api/errors/0ef41b8916f9a6e6. Report an issue: GitHub.