Spring Boot 4 vs Spring Boot 3 — What Changed & Should You Upgrade?
Spring Boot 4 just dropped and it's a BIGGER deal than most people realise. This isn't just a version bump — it's the most structural change to Spring Boot since the move from Boot 2 to Boot 3.
In this video I break down EVERYTHING that changed, show you real code examples, and give you an honest answer to the question I've been getting non-stop: should YOU actually upgrade?
✅ WHAT WE COVER:
Modularization — why your pom.xml is about to change and what Flyway has to do with it
Jackson 3 — what breaks, exact import changes, and the stop-gap property to buy you time
HTTP Service Clients — zero-boilerplate REST calls (like Spring Data JPA but for APIs)
API Versioning — built-in framework-level versioning, no more rolling your own /v1/ /v2/
OpenTelemetry Starter — distributed tracing across microservices with one dependency
Virtual Threads (Java 21) — enable with one line in application.properties
What got REMOVED — Undertow, Spock, Reactive Pulsar, and what to do about each one
8-step migration checklist — from Boot 3.5 to Boot 4.0, in the right order
Decision framework — green / yellow / red: when YOUR team should upgrade
🔗 OFFICIAL RESOURCES:
Release Notes: https://github.com/spring-projects/sp...
Migration Guide: https://github.com/spring-projects/sp...
Reference Docs: https://docs.spring.io/spring-boot/4.0/
Blog — Modularization: https://spring.io/blog/2025/10/28/mod...
Blog — HTTP Clients: https://spring.io/blog/2025/09/23/htt...
Blog — API Versioning: https://spring.io/blog/2025/09/16/api...
💬 DROP A COMMENT with:
Which Boot version you're migrating from
How long the migration took
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