How Maven Multi-Module Builds Can Enforce Spring Boot Architecture at Compile Time

A development team tackled recurring architectural violations in their Spring Boot application by restructuring it into specialized Maven modules instead of relying on package-level separation alone. The core problem was that package boundaries in a single-module project could not stop developers from introducing bad practices, such as injecting EntityManager directly into REST controllers or leaking database schema details to the frontend. Their solution involved splitting the backend into distinct modules — including domain, business-logic, dao-api, dao-impl, and others — and separating the API contract into its own Git repository. By ensuring the business-logic module only depends on interface layers like dao-api and bridge-api, the team made it physically impossible for the compiler to allow direct access to JPA or Hibernate internals from core logic. This approach shifts architectural enforcement from human code review to the build process itself, causing violations to fail at compile time on a developer's local machine.