Enterprise Java teams face mounting technical debt and accelerating security vulnerabilities from outdated Spring versions, a problem amplified by AI‑driven attacks, and Tanzu Spring offers a six‑year extended lifecycle, automated upgrade tooling, AI‑integrated governance, and 24/7 vendor support to safely modernize their applications.
This article explains why staying on old Java and Spring Boot versions is risky, introduces a dual‑axis model for the upgrade, details Java 21‑to‑25 language and JVM improvements, outlines Spring Boot 3.5‑to‑4.0 structural changes, and provides a step‑by‑step manual and OpenRewrite migration workflow with verification guidelines.
This practical guide walks you through every stage of upgrading a Spring Boot 2.x application to 3.x, covering pre‑migration preparation, dependency changes, code refactoring, security configuration updates, configuration file adjustments, third‑party library compatibility, common pitfalls, verification steps, and optional native image building.
