static ContainerizingMode getContainerizingModeChecked(
      RawConfiguration rawConfiguration, ProjectProperties projectProperties)
      throws InvalidContainerizingModeException {
    ContainerizingMode mode = ContainerizingMode.from(rawConfiguration.getContainerizingMode());
    if (mode == ContainerizingMode.PACKAGED && projectProperties.isWarProject()) {
      throw new UnsupportedOperationException(
          "packaged containerizing mode for WAR is not yet supported");
    }
    return mode;
  }
Gets the value of the {@code appRoot} parameter. If the parameter is empty, returns {@code
/var/lib/jetty/webapps/ROOT} for WAR projects or {@link JavaContainerBuilder#DEFAULT_APP_ROOT}
for other projects.

@param rawConfiguration raw configuration data
@param projectProperties the project properties
@return the app root value
@throws InvalidAppRootException if {@code appRoot} value is not an absolute Unix path
jib-plugins-common/src/main/java/com/google/cloud/tools/jib/plugins/common/PluginConfigurationProcessor.java