Idiomatic Kotlin applications with Spring Boot 4

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" summary

Gradle Kotlin DSL with Java 25 is the default build path, and Spring Boot 4 raises the Kotlin baseline (4.0 → Kotlin 2.2, 4.1 → 2.3, 4.2 → 2.4) while adding JSpecify-based null-safety checked by NullAway. Kotlin serialization only activates via spring-boot-kotlin-serialization-json and coexists with Jackson for non-@Serializable classes. WebMVC plus virtual threads is the recommended runtime for most services, JPA remains awkward with idiomatic Kotlin data classes, and Spring Boot 4 AOT cache delivers ~2x startup now and aims for ~5x with upcoming Java releases.

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" chapters (17)

1. 0:00Introduction
2. 1:30Idiomatic Kotlin for maintainable code
3. 3:36Kotlin build systems in Spring Boot 4
4. 6:26Spring Boot 4 and Kotlin 2.2 upgrade
5. 7:50Jakarta validation with Kotlin data classes
6. 10:00Null safety with J Specify
7. 13:32WebMVC vs WebFlux with Kotlin
8. 15:41Annotation vs programmatic config
9. 17:49Bean registrar DSL
10. 20:16Logging best practices
11. 22:44Testing Kotlin with Spring Boot
12. 24:49Kotlin serialization in Spring Boot 4
13. 27:37Kotlin persistence with JPA
14. 30:27Coroutines observability
15. 32:12Spring AI Kotlin support
16. 35:42Faster startup with AOT cache
17. 39:10Q&A

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