@Override
  public JibContainerBuilder runPluginExtensions(
      List<? extends ExtensionConfiguration> extensionConfigs,
      JibContainerBuilder jibContainerBuilder)
      throws JibPluginExtensionException {
    if (extensionConfigs.isEmpty()) {
      log(LogEvent.debug("No Jib plugin extensions configured to load"));
      return jibContainerBuilder;
    }

    // Add the injected extensions at first to prefer them over the ones from JDK service
    // loader.
    // Extensions might support both approaches (injection and JDK service loader) at the same
    // time for compatibility reasons.
    List<JibMavenPluginExtension<?>> loadedExtensions = new ArrayList<>(injectedExtensions);
    loadedExtensions.addAll(extensionLoader.get());
    JibMavenPluginExtension<?> extension = null;
    ContainerBuildPlan buildPlan = jibContainerBuilder.toContainerBuildPlan();
    try {
      for (ExtensionConfiguration config : extensionConfigs) {
        extension = findConfiguredExtension(loadedExtensions, config);

        log(LogEvent.lifecycle("Running extension: " + config.getExtensionClass()));
        buildPlan =
            runPluginExtension(extension.getExtraConfigType(), extension, config, buildPlan);
        ImageReference.parse(buildPlan.getBaseImage()); // to validate image reference
      }
      return jibContainerBuilder.applyContainerBuildPlan(buildPlan);

    } catch (InvalidImageReferenceException ex) {
      throw new JibPluginExtensionException(
          Verify.verifyNotNull(extension).getClass(),
          "invalid base image reference: " + buildPlan.getBaseImage(),
          ex);
    }
  }
Returns Spring Boot {@code <configuration>} if the Spring Boot plugin is configured to run the
{@code repackage} goal to create a Spring Boot artifact.
jib-maven-plugin/src/main/java/com/google/cloud/tools/jib/maven/MavenProjectProperties.java