Spring Boot Best Practices for Building Robust Microservices

Spring Boot is the most popular Java framework for developing microservices. Since 2016 the author has gathered personal experience and insights from other Spring Boot experts into a set of best practices that apply both to Spring Boot projects and to Spring applications in general.

1. Use a custom BOM to manage third‑party dependencies – Create a platform‑bom (similar to Spring IO Platform) and import it in all modules so that upgrading a dependency only requires changing a single version entry.

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>io.spring.platform</groupId>
            <artifactId>platform-bom</artifactId>
            <version>Cairo-SR3</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

2. Leverage auto‑configuration – Rely on Spring Boot Starters (e.g., spring-boot-starter-data-redis, spring-boot-starter-data-mongodb) to avoid manual configuration and the dreaded "Jar hell". Exclude unwanted auto‑config classes only when absolutely necessary.

@EnableAutoConfiguration(exclude = {ClassNotToAutoconfigure.class})

3. Start projects with Spring Initializr – Use https://start.spring.io/ to generate a tested, dependency‑managed skeleton that follows Spring’s auto‑configuration conventions.

4. Create custom auto‑configuration for common organizational concerns – When many teams share the same problems, encapsulate the solution in a reusable auto‑configuration library.

5. Design a clear source‑code package structure – Avoid the default package, keep the main class (e.g., Application.java) at the top level, and group controllers and services by feature or keep all controllers together, but stay consistent.

6. Keep @Controller classes simple and focused – Controllers should be stateless, delegate business logic to services, handle only HTTP concerns, and be designed around use‑cases (see GRASP Controller pattern).

7. Build @Service beans around business capabilities – Name services after domain concepts (e.g., AccountService, UserService) rather than technical concerns like DatabaseService.

8. Isolate database access from core business logic – Follow the principles of "Clean Architecture" so that services do not depend on a specific database implementation.

9. Protect business logic from Spring‑specific code – Keep core domain code free of Spring annotations to maintain reusability and testability.

10. Prefer constructor injection – It makes beans easier to instantiate without Spring and eliminates the need for @Autowired on fields.

11. Understand the concurrency model – Controllers and services are singletons by default; be aware of thread‑safety issues and configure thread pools appropriately, especially when using WebFlux.

12. Externalize configuration – Use Spring Cloud Config or environment‑variable‑based configuration to manage settings across multiple services.

13. Provide global exception handling – Implement a HandlerExceptionResolver or use @ExceptionHandler on controllers for consistent error responses.

14. Use a proper logging framework – Obtain a logger via LoggerFactory.getLogger(MyClass.class) instead of System.out.println to control log levels.

15. Test your code – Write unit and integration tests; consider Spring Cloud Contract for consumer‑driven contracts.

16. Use test slices – Load only the parts of the application needed for a test (e.g., @WebMvcTest, @DataJpaTest) to speed up execution and keep tests focused.

By following these practices, developers can build Spring Boot‑based microservices that are easier to maintain, scale, and evolve over time.