1. Inventory your estate
Start with what you have: the Mule applications, their flows, the DataWeave scripts, the connectors each one uses, and the tests (Postman collections, MUnit) that describe expected behaviour. Those tests are the asset that makes a safe migration possible — they become the oracle for parity.
2. Translate the logic — DataWeave and connectors
The bulk of the work is DataWeave (usually 60–70% of the effort) plus the connectors. Connectors translate onto their idiomatic Spring equivalents (JdbcTemplate, KafkaTemplate, WebClient, and so on). DataWeave keeps working without a rewrite — it runs on the embedded, DataWeave-compatible Transmute engine as editable scripts your team already understands (direct DataWeave-to-Java translation is on the roadmap). The connector and DataWeave guides in these resources cover the details.
The goal is idiomatic Spring Boot you own outright — standard Java with no runtime dependency on the migration tool — not a Mule emulation layer bolted onto Java.
3. Prove parity before you touch production
This is the step that de-risks everything. Replay your existing tests against both the original Mule app and the converted Spring Boot app, and compare every response field, scoring MATCH or MISMATCH. Non-deterministic fields (timestamps, generated IDs) are checked for shape and type instead of exact value. You cut over only what is proven equivalent.
4. Cut over with the strangler pattern
Run the converted service alongside the original Mule app. Shift traffic gradually — a canary slice first, then more as confidence builds — using your existing gateway or router. Because the generated Spring Boot has no dependency on the migration tool, rollback at any point is just reverting a deploy and pointing traffic back at the still-running Mule app.
Field-by-field parity validation is what makes this safe: it is the canary oracle. You are never guessing whether the new service matches — you have measured it.
5. Decommission and repeat
Once traffic is fully on the Spring Boot service and stable, decommission the Mule app and move to the next one. The estate shrinks application by application, each step measured and reversible, until Anypoint Platform is no longer on the critical path.
FAQ
Do I have to migrate my whole MuleSoft estate at once?
No. The reliable approach is incremental — convert and cut over one application at a time using the strangler pattern, proving parity on each before decommissioning the original. The estate shrinks application by application, each step measured and reversible.
How do I de-risk a MuleSoft migration?
Use your existing tests as the oracle: replay them against both the original Mule app and the converted Spring Boot app and compare every response field, scoring MATCH or MISMATCH. Cut over only what is proven equivalent, and keep the Mule app running until traffic is fully shifted so rollback is trivial.