This article details the practical challenges and solutions when migrating from Spring Boot 3.x to 4.x, focusing on the Jackson 2 to 3 transition including package changes, exception handling updates, annotation exceptions, immutable ObjectMapper configuration, and coexistence strategies for legacy dependencies.
Spring AI 2.0 reaches GA, offering a production‑grade, Java‑first AI development path tightly integrated with Spring Boot 4.x, Spring Framework 7.0, and the Model Context Protocol, while introducing upgraded agent tooling, Jackson 3, JSpecify annotations, and streamlined provider SDKs.
Spring Boot 4.1.0 builds on the 4.x foundation by adding production‑focused enhancements such as native gRPC auto‑configuration, outbound SSRF protection, lazy JDBC connections, OpenTelemetry support, and updated Jackson 3 settings, while offering guidance on when and how to upgrade.
Upgrading to Spring Boot 4 brings Jackson 3, which reorganizes packages, replaces ObjectMapper with JsonMapper, changes the default date format to ISO‑8601, and converts checked exceptions to RuntimeException, requiring developers to adapt code, adjust configurations, and understand the design rationale to avoid runtime bugs.
Spring Boot 4 upgrades its default JSON processor to Jackson 3, introducing new package names, immutable builders, ISO‑8601 date serialization, and removal of checked exceptions, while preserving annotation compatibility for a smooth migration.
