Spring Framework 7 and Spring Boot 4 Deliver API Versioning, Resilience, and Null-Safe Annotations

"Broadcom released Spring Framework 7.0 (announced here) and Spring Boot 4.0 (announced here) in November 2025. This new generation introduces first-class REST API versioning, JSpecify annotations for standardized null safety across the Spring portfolio, and built-in resilience features such as retry and concurrency throttling. Spring Boot 4 migrates to Jackson 3 for JSON processing and splits the monolithic autoconfigure JAR into modules."

"The new API versioning feature is now available in Spring MVC and Spring WebFlux. The framework supports path, header, query parameter, and media type versioning strategies. Controllers are configured through ApiVersionStrategy and declare versions directly on mappings such as: @GetMapping(url = "/accounts/{id}", version = "1.1" They also have built-in deprecation handling compliant with RFC 9745. The RestClient, WebClient, and HTTP interface clients use the ApiVersionInserter, as do the non-reactive RestTestClient (new in 7.0) and WebTestClient."

"Spring Framework 7 completes the migration to standardized JSpecify annotations for null safety across the Spring portfolio. The JSpecify collective includes OpenJDK, Broadcom, Google, JetBrains, and Sonar. Annotations such as @Nullable and @NonNull apply to standard and generic types, arrays, and vararg elements. Kotlin 2 automatically translates JSpecify annotations into Kotlin nullability. IntelliJ IDEA 2025.3 provides first-class support with full coverage, including complex data-flow analysis. Build-time checking with the NullAway project requires at least JDK 21, though JDK 17 support may materialize."

Spring Framework 7.0 and Spring Boot 4.0 add first-class REST API versioning, JSpecify null-safety annotations, and built-in resilience features such as retry and concurrency throttling. Spring Boot 4 migrates to Jackson 3 for JSON processing and splits the monolithic autoconfigure JAR into modular artifacts. Spring Framework 7 retains a JDK 17 baseline while embracing JDK 25 and adopts Jakarta EE 11 and Kotlin 2.2 as new baselines. API versioning is available for Spring MVC and WebFlux with multiple strategies and RFC 9745-compliant deprecation handling. ApiVersionInserter integrates into RestClient, WebClient, HTTP interfaces, and test clients. JSpecify annotations apply broadly and are translated into Kotlin nullability, with IDE and build-time checking support evolving.

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