void afterUnmarshal(Unmarshaller unmarshaller, Object parent) {
    initializeProcessingComponentMappings();
    initializeAddComponentTasks();
  }
This method is called after all the properties (except IDREF) are
unmarshalled for this object, but before this object is set to the parent
object. This is done automatically by the {@link Unmarshaller}.
<p/>
Currently, this method performs the following post-unmarshal operations:
<ul>
<li>Builds a mapping of service name to a mapping of component name to
{@link ProcessingComponent}</li>
</ul>

@param unmarshaller
         the unmarshaller used to unmarshal this instance
@param parent
         the parent object, if any, that this will be set on.
@see Unmarshaller
ambari-server/src/main/java/org/apache/ambari/server/stack/upgrade/UpgradePack.java