spring-boot
Spring Boot backends (Boot 4 / Framework 7)
A Spring Boot app is a thin web layer delegating to a transactional service layer over
Spring Data JPA repositories — wired by constructor injection, configured by typed
@ConfigurationProperties, locked down by a SecurityFilterChain bean. Controllers
validate input and delegate; they never own business logic, transactions, or persistence.
Hold that shape and most "where does this go?" questions answer themselves.
Pinned stack (verify against the project's pom.xml/build.gradle — do not assume):
Spring Boot 4.0 (GA 2025-11-20), Spring Framework 7, Java 17 baseline / Java 25 LTS, Jakarta
EE 11 (jakarta.*, never javax.*), Jackson 3, Spring Security 7, Spring Data JPA /
Hibernate 7, JUnit 5 + Testcontainers, Maven 3.9 / Gradle.
If you are typing WebSecurityConfigurerAdapter, @MockBean, field @Autowired,
authorizeRequests, or javax.persistence — stop. Those are the previous generation.
The modern idioms below replace every one of them.