Next level Kotlin support in Spring Boot 4
summary
Spring Boot 4 uses Kotlin 2.2 baseline and adds JSpecify null-safety annotations so Kotlin callers get compile-time null errors without extra flags; a new bean-registration DSL replaces the old ApplicationContextInitializer-based approach for library-discoverable, AOT-friendly bean wiring; Kotlin reflection moves toward kotlin-metadata JVM, making startup overhead drop from 15% to 2% and memory overhead from ~20% to nearly zero in tests; CDS/AOT cache yields ~2x startup and 20% memory savings today, with up to 4x planned.
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chapters (17)
- 0:00Introduction
- 0:40Kotlin support
- 1:30New strategic partnership
- 2:03Spring Boot 4
- 3:07New Safety
- 4:09How it works
- 5:46Portfol Data
- 6:41Bin Registration DSL
- 8:05Bin Registry API
- 9:58Bin Register DSL
- 11:59Kotlin Reflect
- 14:28Inline Value Classes
- 15:27CDS AOT Cache
- 20:46Spring AI Kotlin support
- 23:49Spring Kotlin reference application
- 29:17Spring Kotlin demo
- 36:24Kotlin front end
