Enhancing a dinosaur – clean(?) modification of SAP objects with “USEREXIT” Forms

[CreyJ]

Assuming you have the chance to start up wit a new ERP or S/4 SAP system - yes they are also still alive in an S/4 Hana -  and you can work on an untouched SAPMV45A (as example). How would you do it? What is clean (for you)?

Here are some of my thoughts – but no final conclusion. Maybe you can add yours.

• Direct implementation in ZZ include:
  
  
  
  • Pros
    
    
    
    • Direct access to all data objects
    
    
    • Easiest way
    
    
    
    
  
  
  • Cons
    
    
    
    • Complete include locked by one change
    
    
    • No unit tests
    
    
    • Direct access to all data objects, when doing it wrong (ok that's always the case when doing it wrong, but ... )
    
    
    
    
  
  
  
  

• Direct implementation using includes, one (or more) per USEREXIT form :
  Similar like direct implementation
  
  
  
  • Pros
    
    
    
    • several developers/projects can work in parallel
    
    
    
    
  
  
  • Cons
    
    
    
    • Looks a little bit like fake modularization, as include is not an own object
    
    
    • Tendency to grow wild. “May-be another include in or after the original include helps me with my problem?”
    
    
    • A return or check statement  leaves the subroutine and not just the include
    
    
    
    
  
  
  
  


• External performs to programs, that share the data object with tables/common part
  
  
  
  • Pros:
    
    
    
    • Still direct access to data
    
    
    • Can have own screens
    
    
    • Implementation could be done by local classes and unit tests
    
    
    
    
  
  
  • Cons
    
    
    
    • External performs look like a misuse of the private objects, that are public by technical reasons.
    
    
    
    
  
  
  
  

• Real OO with global interfaces/classes/BAdis
  
  
  
  • Pros
    
    
    
    • Advantages of OO: Encapsulation, Inheritance ..
    
    
    • “Modern” Exception handling
    
    
    • Development support by ADT
    
    
    • Unit tests
    
    
    
    
  
  
  • Cons
    
    
    
    • Cannot have screens
    
    
    • Frequent changes of public interface when starting with a reduced/minimal interface
    
    
    
    
  
  
  • Variants
    
    
    
    • One class/interface/BADI per main program / one instance per document/transaction
      
      
      
      • Pros
        
        
        
        • Can have own attributes / member variables
        
        
        
        
      
      
      • Cons
        
        
        
        • May result in large classes/interfaces
        
        
        • more complicated to handle, see also https://github.com/SAP/styleguides/blob/main/clean-abap/CleanABAP.md#make-singletons-only-where-mult...
        
        
        
        
      
      
      
      
    
    
    • One class/interface/BADI per USEREXIT form
    
    
    
    
  
  
  
  


• How to perform the modification
  
  
  
  • Modification of the SAP include
    
    
    
    • Pros
      
      
      
      • Easier to transport in an running system
      
      
      
      
    
    
    • Cons
      
      
      
      • Needs a registry key
      
      
      • More complicated in SPAU
      
      
      
      
    
    
    
    
  
  
  • Implicit enhancement
    
    
    
    • Pros
      
      
      
      • No key needed
      
      
      • Easier in SPAU
      
      
      • Can have a different transport route than a modified SAP object
        e.g. when applying notes in a central development system
      
      
      
      
    
    
    • Cons
      
      
      
      • Import of an enhancement creates a new runtime object. So it cannot be imported that easy in a running system.
      
      
      
      
    
    
    
    
  
  
  
  

 

Currently my thoughts go in direction of having a program that shares the data with the master program. The call from the USEREXIT form is done by external subroutine call:

E.g. like this for USEREXIT_FIELD_MODIFICATION.

perform field_modification in program <your program> if found.

Starting point for the implementation of the custom code would be a local class, as there are easy refactoring paths to  global classes.

The modification would be done using an implicit enhancement.

Let me know your thoughts.