What’s New in Spring Boot 4.0? Core Dependencies, Virtual Threads, and More

Core Dependencies

Java version: minimum Java 17, strongly recommended Java 21 (enables virtual threads) and Java 25.

Specification base: upgraded to Jakarta EE 11.

Web container: mandatory Servlet 6.1.

✅ Supported containers: Tomcat 11.0, Jetty 12.1.

⚠️ Removed support: Undertow (not yet compatible with Servlet 6.1).

Key Features Overview

Spring Framework 7.0 provides the solid foundation for Spring Boot 4.0.

Concurrency revolution: Virtual Threads become the core concurrency model, dramatically increasing single‑machine throughput.

Developer experience improvements: @RequestMapping Version: API version control for efficient routing of version‑specific requests. @HttpServiceClient: native declarative HTTP client that replaces OpenFeign. JdbcClient & JmsClient: new fluent APIs that make code more concise and readable.

Architecture slimming: deep modularization refactor improves GraalVM native image startup speed and memory efficiency.

Built‑in resilience: core integration of @Retryable and @ConcurrencyLimit eliminates the need for external circuit‑breaker libraries.

Version Guidance

For projects currently on Spring Boot 3.x, it is strongly recommended to upgrade to the latest 3.5 release first.

Spring Boot 3.5 is the final major release of the 3.x line; open‑source support continues until June 2026, commercial support until June 2032.

3.5 introduces key features and migration mechanisms that smooth the transition to Spring Boot 4.x.

Technical reference repository (relevant to Spring ecosystem): https://gitee.com/log4j/pig