Is your Spring Boot app secretly turning into a big ball of mud? 🧶 Spring Modulith helps you keep a single deployable app, but with clear module boundaries, tests, and diagrams enforced by the framework instead of “hope and conventions”.
🔸 TL;DR
▪️ Spring Modulith helps you build modular monoliths on top of Spring Boot.
▪️ Each business module = package with clear public API vs internals.
▪️ It can verify architecture rules, test modules in isolation, and generate diagrams/docs from the code.
▪️ You keep the simplicity of a monolith, while preparing for possible future microservices if needed.
🔸 WHAT IS SPRING MODULITH?
▪️ An opinionated toolkit from the Spring team to build domain-driven, modular apps on top of Spring Boot.
▪️ It encourages you to slice your app by business capabilities (catalog, orders, billing…) instead of technical layers.
▪️ Modules live as first-class citizens: they expose an API, hide internals, and define how they talk to each other.
🔸 KEY SUPERPOWERS
▪️ Explicit module boundaries
You define modules (packages) and Modulith checks that no one bypasses the rules “just this once”.
▪️ Architecture verification as tests 🧪
Architecture rules run in your build; a bad dependency = failing test, not a future refactoring nightmare.
▪️ Module-level integration tests
You can load and test a single module in isolation instead of always booting the full app.
▪️ Events between modules 📬
Modules can communicate via events instead of direct calls, reducing coupling and making evolution easier.
▪️ Generated diagrams & docs 🧾
From your module model, Modulith can generate PlantUML diagrams and Asciidoc snippets, so architecture docs stay up to date.
🔸 WHEN TO CONSIDER IT?
▪️ Growing Spring Boot monolith that starts to feel messy.
▪️ Team split in feature teams (each owning a domain/module).
▪️ You want a clean architecture now, but keep the option to move to microservices later.
🔸 TAKEAWAYS
▪️ You don’t have to jump to microservices to do serious architecture.
▪️ Spring Modulith gives you structure, guardrails, and visibility inside a single Spring Boot app.
▪️ Architecture becomes observable and testable, not just “drawn in a Confluence page”.
▪️ It’s a great fit if you want DDD + Spring Boot without the distributed systems tax.
#️⃣ #Java #SpringBoot #SpringModulith #ModularMonolith #SoftwareArchitecture #CleanArchitecture #DDD #Microservices #JavaDeveloper
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