Spring Boot 4.0 & Spring Framework 7: Deep Dive into New Features and Migration Guide

Release Overview

In November, the Spring team launched a coordinated set of major releases: Spring Framework 7, Spring Boot 4, Spring Data 2025.1, and Spring AI 1.1. This is not a routine upgrade but a deep restructuring of the entire Spring ecosystem.

Core Platform Upgrades

JDK and Jakarta EE : Spring Framework 7 retains compatibility with JDK 17 but recommends the latest LTS, JDK 25, and adopts Jakarta EE 11 as the new baseline.

All legacy javax.* packages are removed; annotations such as @javax.annotation.PostConstruct and @javax.inject.Inject must be migrated to the jakarta.* namespace.

Servlet 6.1 (Tomcat 11.0 / Jetty 12.1), JPA 3.2 (Hibernate 7.1/7.2), Bean Validation 3.1 (Hibernate Validator 9.0+), WebSocket 2.2, Kotlin 2.2, and GraalVM 25 are now the default components.

Null‑Safety Revolution

The framework now fully embraces JSpecify annotations, replacing the older JSR‑305 style. This brings precise null‑safety semantics for generics, arrays, and var‑args, improving Kotlin‑Java inter‑operability.

Build‑Time Optimizations (Project Leyden)

Spring’s traditional “runtime magic” (classpath scanning, dynamic proxies, reflection, conditional auto‑configuration) is being shifted to build time. The goal is to move everything that can be resolved during compilation into the build phase, resulting in faster startup and lighter native images.

Modern HTTP Client & Test Toolchain

RestTemplate

is now deprecated (will be marked @Deprecated in 7.1).

Declarative HTTP client introduced via @HttpExchange with automatic implementation generation and group‑level configuration via @ImportHttpServices.

New RestTestClient replaces WebTestClient for non‑reactive testing, supporting both MockMvc and real server scenarios.

Jackson 3 Full‑Stack Support

Spring now defaults to tools.jackson (Jackson 3.x) while deprecating Jackson 2, which will be removed in Spring 7.2. Migration helpers remain in com.fasterxml.jackson, and the preferred way to create a mapper is JsonMapper.builder().

Native API Versioning

Both Spring MVC and WebFlux provide built‑in API version management via request headers, parameters, or media types. Configuration properties are now under spring.mvc.apiversion.* and spring.webflux.apiversion.*, with support for deprecation markers.

Built‑In Resilience

Spring now treats failure as the default state of distributed systems. Core resilience features—retry, rate limiting, circuit breaking—are integrated directly into spring-core using annotations like @Retryable(maxAttempts = 3). No external spring-retry or Resilience4j configuration is required.

Modular Auto‑Configuration

Auto‑configuration modules have been split into finer‑grained units, improving IDE diagnostics, reducing AOT code generation size, and narrowing the analysis scope for native images.

OpenTelemetry Integration

The new spring-boot-starter-opentelemetry starter brings first‑class support for metrics, traces, and logs, tightly integrated with Micrometer and exporting via OTLP.

Spring AI Dual‑Track Strategy

Spring AI 1.1 (stable): quick starter integration with major LLM providers, automatic MCP/JSON mapping, and declarative tool registration via ChatClient.

Spring AI 2.x (future‑focused): rebuilt for Spring Boot 4 and Jakarta EE 11, refactored ChatClient API, full JSpecify null‑safety support, and deep MCP/AOT integration.

Two clear migration paths emerge:

Spring Framework 6 + Spring Boot 3 + Spring AI 1.1 – stable, mature, suited for long‑term maintenance.

Spring Framework 7 + Spring Boot 4 + Spring AI 2.x – aggressive, forward‑looking, targeting the next decade of development.

Overall, Spring Boot 4 and Spring Framework 7 deliver a modern, cloud‑native Java stack with stronger compile‑time guarantees, built‑in resilience, and native observability.