Component Scanning

How Component Scanning Works

com.example.app/           ← @SpringBootApplication here
├── controller/             ← Scanned ✓
│   └── ProductController
├── service/                ← Scanned ✓
│   └── ProductService
├── repository/             ← Scanned ✓
│   └── ProductRepository
└── util/                   ← Scanned ✓
    └── Helper

What Gets Scanned

Annotation	Package	Purpose
@Component	Any	Generic Spring-managed component
@Service	Service layer	Business logic
@Repository	Data layer	Database access
@Controller	Web layer	MVC controllers
@RestController	Web layer	REST API controllers
@Configuration	Config	Bean definitions

Custom Scan Paths

@SpringBootApplication
@ComponentScan(basePackages = "com.example.core")
public class Application { }

Filtering

@ComponentScan(
    basePackages = "com.example",
    includeFilters = @ComponentScan.Filter(
        type = FilterType.ANNOTATION,
        classes = CustomAnnotation.class
    ),
    excludeFilters = @ComponentScan.Filter(
        type = FilterType.ASSIGNABLE_TYPE,
        classes = TestHelper.class
    )
)

Configuration

• Use properties over YAML for simple configs
• Externalize configuration
• Use profiles for environments
• Validate on startup

Bean Management

• Prefer constructor injection
• Use appropriate scope
• Implement lazy initialization
• Clean up resources

Security

• Use Spring Security
• Implement CSRF protection
• Use method-level security
• Log security events

Key Points

• Understanding Component Scanning is essential for production systems
• Always consider scalability and maintainability
• Test thoroughly before deploying to production
• Monitor performance and set up alerting

Common Patterns

1. Validation: Always validate input at the boundary
2. Error Handling: Use structured error responses
3. Logging: Log key events for debugging
4. Testing: Unit, integration, and load tests
5. Documentation: Keep docs updated with code changes