As Spring Boot applications grow from small demos to production systems, best practices become critical.
Following proven patterns helps you build applications that are maintainable, scalable, testable, and reliable.

This post consolidates real-world Spring Boot best practices you should follow in professional projects.

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1. Follow a Clean Package Structure

Use a clear, layered structure:

com.example.app
 ├── controller
 ├── service
 ├── repository
 ├── dto
 ├── config
 └── exception

Benefits:

• Easy navigation
• Clear separation of concerns
• Better readability and maintenance

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2. Keep @SpringBootApplication in the Root Package

Place the main class at the root of your project package.

@SpringBootApplication
public class AppApplication { }

This ensures:

• Correct component scanning
• No missing beans
• Predictable startup behavior

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3. Prefer Constructor Injection

Always prefer constructor injection over field injection.

@Service
public class OrderService {

    private final PaymentService paymentService;

    public OrderService(PaymentService paymentService) {
        this.paymentService = paymentService;
    }
}

Why:

• Immutability
• Easier testing
• Clear dependencies

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4. Use Configuration Properties for Settings

Group related configuration using @ConfigurationProperties.

@ConfigurationProperties(prefix = "app")
public class AppConfig {
    private int timeout;
}

Avoid scattering @Value everywhere.

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5. Externalize Configuration

Never hardcode environment-specific values.

Use:

• application.yml
• Profiles (dev, test, prod)
• Environment variables

This makes applications portable and secure.

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6. Use Profiles for Environment Separation

spring.profiles.active=dev

Create:

• application-dev.yml
• application-prod.yml

Avoid if-else logic for environment checks.

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7. Handle Exceptions Globally

Use @ControllerAdvice for centralized error handling.

@RestControllerAdvice
public class GlobalExceptionHandler { }

Benefits:

• Consistent API responses
• Cleaner controllers
• Easier debugging

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8. Avoid Heavy Logic in Controllers

Controllers should:

• Accept requests
• Delegate to services
• Return responses

Business logic belongs in the service layer.

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9. Use DTOs Instead of Entities

Never expose JPA entities directly in APIs.

Use DTOs to:

• Control response structure
• Improve security
• Avoid lazy loading issues

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10. Enable Logging Properly

Use SLF4J with Logback.

private static final Logger log = LoggerFactory.getLogger(MyClass.class);

Avoid:

• System.out.println
• Excessive logging in production

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11. Keep Startup Fast

• Avoid heavy logic in constructors
• Avoid blocking calls at startup
• Use lazy initialization when appropriate

Fast startup improves cloud scalability.

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12. Validate Inputs Early

Use Bean Validation:

@NotNull
@Email
private String email;

Validate at controller boundaries to avoid downstream errors.

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13. Use Actuator in Production

Enable Spring Boot Actuator for:

• Health checks
• Metrics
• Application insights

This is critical for monitoring.

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14. Write Tests Early

• Unit tests for services
• Integration tests for controllers
• Use Spring Boot Test utilities

Testing prevents regressions and improves confidence.

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15. Summary

• Use clean architecture and package structure
• Prefer constructor injection
• Externalize configuration
• Separate concerns properly
• Handle exceptions globally
• Write tests and monitor applications

Following these practices leads to robust, professional Spring Boot applications.

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What's Next?

Next post:

32 - application.properties vs application.yml

We’ll compare configuration formats and decide when to use each.