unknown

Masabi, a mobility-as-a-service platform powering public transit ticketing for major cities including New York's MTA, shares how they migrated a decade-old Java codebase to Kotlin Multiplatform. The system spans embedded gate validators, Android/iOS mobile apps, and backend services. The migration moved away from J2ObjC (Java-to-Objective-C transpilation) to KMP, driven by concerns about J2ObjC's stagnating support and the desire to unify the tech stack. The team took an incremental approach: first modularizing the monorepo, then migrating small helper libraries as safe proving grounds, keeping Java tests in place to validate Kotlin production code before migrating tests themselves. The translation process evolved through three eras—manual/IntelliJ converter, early ChatGPT copy-paste, and finally agentic IDE tools like JetBrains AI and Junie—dramatically accelerating the work. Challenges included nullability decisions, lack of parameterized test support in common Kotlin tests (solved with a custom KSP processor), and replacing Java standard library APIs like java.time with kotlinx-datetime and HTTP clients with Ktor.

How Major Metros Run on Kotlin Multiplatform | Talking Kotlin #145

News and articles related to Kotlin and Compose Multiplatform