The DARApplier (DataAlterationRequest Applier) is an interesting sort of component that is tightly coupled to the RSF serialization framework. It is integral to the principal behind RSF that request parameters represent transformations on the data model rather than just specifically submitted data. It is this idea that enables the RequestSubmittedValueCache (RSVC) to function as a running "transaction log" of activities, and hence our repository of state in a MultiRequest.

The DARApplier is the component which actually applies the contents of the RSVC to the data model - it has responsibilities for decoding EL references, navigating through the bean model, and reflectively invoking the required manipulation, encoded as a DataAlterationRequest. It is only within the DARApplier that the target type referenced by an EL can be known since the bean path is parsed at this time - therefore it is here that any type conversion is invoked, from the "flat" version of the data that is (probably) stored in the SubmittedValueEntry and DataAlterationRequest representations. Any conversion errors occuring during this delivery process are accumulated into a TargettedMessageList for ultimate delivery to the UI in some form.