RAP : How do you model complex validations & error handling without breaking Fiori UX

[afrad1212_6]

Hello SAP Community,

I would like to get guidance and best practices from the community and SAP experts.

Project Context

• Technology: RAP (ABAP Cloud)
• UI: Fiori Elements (Object Page + List Report)
• Backend: S/4HANA
• Business Object with:
  • Draft enabled
  • Multiple child entities
  • Complex business validations

Real Problem Statement

In our project, we have complex validations such as:

• Cross‑entity checks (header + items)
• Checks against existing records
• Conditional validations based on status, user role, or business rules

We implemented validations using:

• RAP validation methods
• FAILED, REPORTED, and %msg handling

Technically, this works — but the user experience is not always optimal.

Issues We Are Facing

• Errors sometimes appear late (only on Save)
• Messages are valid but not contextual enough for business users
• Handling multiple error messages becomes confusing
• Some validations would ideally run earlier, not just on Save
• We want to avoid:
  • Custom UI logic
  • Non‑standard hacks
  • Breaking RAP principles

Questions to the Community 

How do you design validations in RAP for complex business objects without flooding the user with errors?

1. What is the recommended balance between:
   • RAP validations
   • Determinations
   • Frontend behavior (without custom UI code)?
2. Do you follow any patterns for:
   • Grouping related validation messages
   • Showing errors closer to the field instead of generic messages?
3. Are there real‑project best practices SAP recommends but are not well documented?

What We Want to Achieve

• Clean RAP implementation
• Predictable and user‑friendly Fiori behavior
• Clear error messages that business users understand
• Scalable design (future rules will be added)

kind regards,

Mohammad Afrad Husain. 

[ganeshkanwa]

Hello afrad1212_6,

To avoid the validation in late save phase, you need to use the PRECHECK.

This requires shifting your validations to PRECHECK implementation which would run before data is brought to transactional buffer.

PRECHECK can be implemented for CRUD operation and Actions as well.