@Input
  @Optional
  public List<String> getExtraClasspath() {
    if (System.getProperty(PropertyNames.CONTAINER_EXTRA_CLASSPATH) != null) {
      return ConfigurationPropertyValidator.parseListProperty(
          System.getProperty(PropertyNames.CONTAINER_EXTRA_CLASSPATH));
    }
    return extraClasspath;
  }
A bean that configures properties of the container run from the image. This is configurable with
Groovy closures and can be validated when used as a task input.
jib-gradle-plugin/src/main/java/com/google/cloud/tools/jib/gradle/ContainerParameters.java