I Built a Production-Ready Spring Boot 4.1.0 SaaS Boilerplate — Here Is What I Learned

Short summary

SpringLaunch API is a production-ready Spring Boot 4.1.0 boilerplate eliminating weeks of repetitive setup. Key learnings: Spring Boot 4 introduces breaking changes in imports and testing, auto-configures DaoAuthenticationProvider, requires separating @Async methods via proxies, recommends Password4j over Argon2, and uses factory methods for JPA entities. Includes JWT/OAuth2, email verification, Docker, GitHub Actions CI, and 42 automated tests.

• •Spring Boot 4.1.0 boilerplate saves weeks on repetitive setup: JWT, OAuth2, email verification, Docker, CI/CD
• •Breaking changes from Boot 3: new import paths, @MockitoBean replaces @MockBean, DaoAuthenticationProvider auto-configured
• •Critical patterns: separate @Async methods through dependency injection to use Spring proxy, use Password4j for password encoding, implement factory methods for JPA entities

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