Hello! I've launched a new course.
Open-source support for Spring Boot 3.5 ended in June 2026. Now is the time to upgrade, not say, “I’ll upgrade someday.” But when you actually look for examples, most blog posts use code from the 4.0 milestone releases, so they often don’t work with the official release.
Therefore, I created a course based on the official releases of Spring Boot 4.1.1, Spring Framework 7, and Java 25, with all code compiled and all tests passing.
✅ Features Unique to This Course
All figures were measured directly.
With a single line of virtual thread configuration, I reduced the time to process 2,000 requests from 5.2 seconds to 0.7 seconds.
I also directly verified that the number of auto-configuration candidates decreased from 279 to 92.
Using the JVM AOT cache makes startup approximately 2.4 times faster.
We’ll complete one project from start to finish. Over 26 lessons, we’ll build up a library shelving API and verify all its behavior with 36 tests.
I’ll show you the actual migration process. We’ll cover the three causes behind the 20 compilation errors encountered while upgrading a 3.5 project to 4.1, along with the subtle configuration changes that the tools don’t tell you about.
We always compare 3.x and 4 code side by side.
📚 What You’ll Learn
A new modularized starter system, Java 25, and virtual threads
Jackson 3, Hibernate 7, RFC 9457 ProblemDetail
Official API versioning:
@GetMapping(version = "2.0"), Deprecation and Sunset headers@Retryableand@ConcurrencyLimitintegrated into the core, HTTP Service Client, BeanRegistrarNull safety using JSpecify and NullAway, JUnit 6,
@MockitoBean, RestTestClient, and Testcontainers 2OpenTelemetry, health probes, container images, and AOT
Migration strategies and hands-on practice for moving from 3.x to 4.
👉 Recommended for those who:
Those who have used Spring Boot 3 and want to properly understand what has changed in version 4
Those who need to upgrade a 3.x service currently in operation to 4.
📦 A total of 26 lessons, approximately 8 hours and 40 minutes of content, along with all the practice code, a configuration cheat sheet, and a migration checklist.
🎁 [To celebrate the launch, a 30% discount will be available for one month.]
🔗 [Course link] https://inf.run/o9pF2
We appreciate your interest! 🙏