From Java WebFlux to Kotlin Coroutines, the Journey...?
summary
A team migrates a Spring Boot REST application from Java WebFlux/Reactor to Kotlin using coroutines and Flow while keeping Spring WebFlux, WebClient, reactive Spring Data and Mongo. They must rebuild mappers, routing and validation, replace Mono/Flux with suspend functions and Flow, handle Reactor pitfalls (Mono.defer vs Mono.just, reading response bodies to close WebClient connections), adapt models for Kotlin null-safety via data classes/extensions, and update about 3,000 Mockito tests; the mapping and test rewrites are the main effort.
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chapters (23)
- 0:00Introduction
- 1:05Application overview
- 2:52Kotlin migration and deps
- 3:56WebFlux and reactivity
- 6:02Functional validation and filters
- 7:31Database and cache
- 8:13REST calls and Mono defer
- 9:56Kotlin basics
- 12:42Kotlin routing
- 15:29Modeling issues
- 16:53Java to Kotlin
- 17:35Null safety and data classes
- 18:39Safe mapping
- 19:40Extensions for readability
- 20:23Reified validation
- 21:48Generic types
- 22:09Coroutines intro
- 22:50Flow and coroutines
- 23:55Coroutine validation
- 25:00Unit tests with Mockito
- 26:23Complex types and casting
- 27:06WebFlux vs coroutines tests
- 27:47Conclusion and key differences
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