The checklist
- •Collect the inputs: the Mule application, its flows and DataWeave scripts, the connector configs, and the existing tests (Postman / MUnit).
- •Generate the Spring Boot project: @RestControllers for listeners, connector beans, translated DataWeave, a complete pom.xml.
- •Review the flagged items: recursive or highly dynamic DataWeave and any unsupported connector configuration should be flagged with the original preserved inline — resolve those by hand.
- •Validate parity: run the existing tests against both the Mule app and the converted app; compare every response field; score MATCH or MISMATCH.
- •Handle non-deterministic fields: timestamps and generated IDs are checked for shape and type, not exact value.
- •Cut over with the strangler pattern: run both side by side, shift traffic gradually, keep the Mule app until traffic is fully moved.
- •Decommission the Mule app and move to the next one.
What to watch for
- •JSON key order — use LinkedHashMap so object field order matches Mule.
- •Response buffer limits — raise WebClient's maxInMemorySize; Mule's HTTP requester has no default limit.
- •Null-safety — translate DataWeave's default with Optional or explicit null checks, not bare field reads.
- •Error semantics — make sure error types and on-error handling map to the equivalent Spring exception handling.