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Mastering Spring Boot 4: From New Features to 3.x Migration

For developers feeling overwhelmed by the 4.x upgrade and performance improvements, we share practical migration experience, decision-making criteria, and solutions.

3 learners are taking this course

Level Basic

Course period Unlimited

Spring Boot
Spring Boot
flyway
flyway
open-telemetry
open-telemetry
es5
es5
virtual thread
virtual thread
Spring Boot
Spring Boot
flyway
flyway
open-telemetry
open-telemetry
es5
es5
virtual thread
virtual thread
News list
may9noy님의 프로필 이미지
may9noy

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Edited

🚀 [New Course Open] Master Spring Boot 4 — From New Features to 3.x Migration

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

  • @Retryable and @ConcurrencyLimit integrated into the core, HTTP Service Client, BeanRegistrar

  • Null safety using JSpecify and NullAway, JUnit 6, @MockitoBean, RestTestClient, and Testcontainers 2

  • OpenTelemetry, 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! 🙏

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