Delegating means to use DelegatingRequestProcessor to let Spring manage all the Struts actions.
It is very easy to operate, just add DelegatingRequestProcessor in Struts config file. In new action class, you can reference Spring bean easy by setter method. AOP is also supportted by this way.
An new Spring configration xml for Struts action introduced, and you must maintain this file by hand. Now no tool can support this feature. My opinion, in Struts action, we just want to reference Spring beans, so trivail setter methods are not neccessary.