Frequently Asked Questions
Everything about migrating MuleSoft to Spring Boot with API Modernizer.
- What does API Modernizer do?
- API Modernizer converts your Mule 4 applications to production-ready Spring Boot automatically, validates them against your existing tests, and reports the ROI — all running inside your own environment.
- Does my code leave my environment?
- No — not if you deploy on-premise. API Modernizer can run entirely inside your own network, VPC, or an air-gapped environment, so your Mule source, the generated Spring Boot code, and your data never leave your infrastructure. There's no upload to us, no third-party cloud, and no third-party LLM in the conversion path — and therefore no vendor sub-processor to add to your security review. For quick trials and the online Playground you can use our hosted service instead, where uploaded source is isolated per job and automatically deleted 15 minutes after completion.
- What is Proven-Parity Migration?
- It's our name for migrating by proof rather than promise: the converted Spring Boot app's behavior is demonstrated to match the original Mule app — your own tests replayed against both systems, every response field scored MATCH or MISMATCH — before anything is decommissioned, instead of being assumed correct.
- How is the migration validated?
- Your existing Postman collection runs against both the original Mule app and the converted Spring Boot app simultaneously. Every response is compared field-by-field and scored MATCH or MISMATCH before you decommission anything.
- Why not just use ChatGPT or a general-purpose AI tool to migrate?
- You can generate Mule-to-Spring-Boot code with a general-purpose LLM — but you're then left to prove it behaves identically, by hand, endpoint by endpoint. That manual verification is the expensive, risky part of any migration, and it's exactly what a generic tool hands back to you. API Modernizer is built around that gap: your existing Postman collection runs against both the original Mule app and the converted Spring Boot app, compared field-by-field and scored MATCH or MISMATCH, so parity is demonstrated rather than assumed. It also converts the whole application — flows, error handlers, scatter-gather, DataWeave, every connector, complete pom.xml — with anything untranslatable flagged in MANUAL_FIXES.md, instead of one snippet at a time. And it runs inside your own environment, so your source never goes to a third-party model.
- What are my options for migrating MuleSoft to Spring Boot?
- There are three common approaches. (1) Manual rewrite — engineers reimplement each flow and DataWeave script by hand; thorough but slow (hundreds of hours per application) and hard to verify. (2) A general-purpose AI or LLM — fast to generate code, but you are left to prove it behaves identically, by hand, endpoint by endpoint, and your source is typically sent to a third-party model. (3) An automated, validation-first migration tool such as API Modernizer — it converts flows, DataWeave, and connectors, then proves functional equivalence by replaying your own tests against both systems and scoring every response field MATCH or MISMATCH before you decommission anything, running inside your own environment. The right choice depends on estate size and how much you need to prove parity before cutover.
- Am I locked into API Modernizer after migration?
- No. Generated Spring Boot code has no runtime dependency on API Modernizer — after migration you own standard Java forever.
- How does production cutover actually work?
- Validation happens before anything touches production: the converted Spring Boot app is proven against your existing tests first. Cutover itself follows your own change-management process — most customers run the converted service alongside the original Mule app for an agreed observation window, shifting traffic gradually as confidence builds, the same pattern you'd use for any production cutover. Because the generated code has no dependency on API Modernizer, rolling back at any point is exactly as simple as reverting a deploy and pointing traffic back to the still-running Mule app.
- What are non-deterministic fields — timestamps, generated IDs — scored on?
- They're excluded from exact-match scoring and checked for shape and type instead, since two independent runs will always produce different timestamps or IDs even when the logic is identical. This is why match rate is reported specifically on deterministic endpoints — it reflects real logic parity, not run-to-run noise.
- What connectors are supported?
- 26+ enterprise connectors are converted automatically, including Database, HTTP, Kafka, AWS S3/SQS/SNS, Salesforce, SAP, ServiceNow, MongoDB, Redis, FTP/SFTP, JMS, LDAP, Workday, SOAP, Azure Service Bus, Anypoint MQ, and more.
- What happens if my app uses a connector that isn't on that list?
- The same mechanism that handles untranslatable DataWeave patterns applies: the connector configuration is flagged in MANUAL_FIXES.md alongside the generated project, with the original Mule configuration preserved inline for reference. No data loss, no silent gaps — you get a working Spring Boot project plus a clear list of exactly what needs a human look.
- How do engagements work?
- Every engagement is scoped to your estate and starts small — a low-commitment pilot on one real application, where you get the converted Spring Boot project, the field-by-field parity report, and an ROI analysis, and you keep everything either way. From there we scale to your portfolio at a pace you set. Tell us about your estate and we'll put together a plan that fits it, or model your own savings with the ROI calculator.
- What does ongoing support look like?
- A named point of contact for the length of the engagement and business-hours support, with the same MATCH/MISMATCH validation and ROI reporting applied continuously as you convert further applications — not a one-time pilot mechanic. If your pipeline needs batch or CI/CD-integrated conversion rather than one application at a time, that's scoped as part of the engagement.
- Is API Modernizer SOC 2 or ISO 27001 certified?
- Not yet. Both are on the roadmap with controls already aligned — OWASP Top 10 (2021) review is complete today, and GDPR-oriented data minimisation is built in by design. Because API Modernizer can run entirely inside your own environment, many teams satisfy their security requirements through the on-premise deployment while those certifications are in progress.
- What's the difference between Transmute and API Modernizer?
- Transmute is the DataWeave-compatible transformation engine and DSL that powers the conversions. API Modernizer is the platform — deploy, convert, validate, and report — built on top of it.
- How long does a pilot take?
- About two weeks for one Mule application: the converted Spring Boot project, a functional comparison report, and a personalised ROI analysis.