spring-boot-patterns

name	spring-boot-patterns
description	Spring Boot patterns for Xeres including constructor injection, @Transactional boundaries, REST controllers with OpenAPI annotations, and reactive WebClient usage in the UI module.

Spring Boot Patterns for Xeres

Application Entry Point

@SpringBootApplication(scanBasePackageClasses = {
		io.xeres.app.XeresApplication.class,
		io.xeres.ui.UiStarter.class
})
public class XeresApplication

Service Patterns

Constructor Injection

Always use constructor injection. Dependencies are final.

@Service
public class ContactService
{
	private final ProfileService profileService;
	private final LocationService locationService;

	public ContactService(ProfileService profileService, LocationService locationService)
	{
		this.profileService = profileService;
		this.locationService = locationService;
	}
}

Transactional Boundaries

@Transactional(readOnly = true)
public List<Contact> getContacts()
{ ...}

@Transactional
public void saveContact(Contact contact)
{ ...}

Circular Dependencies

Use @Lazy annotation, but avoid them if possible:

public ContactService(@Lazy ProfileService profileService)
{ ...}

REST Controllers

OpenAPI Annotations

@RestController
@Tag(name = "Profiles", description = "Profile management")
public class ProfileController
{
	@GetMapping("/{id}")
	@Operation(summary = "Get profile by ID")
	@ApiResponse(responseCode = "200", description = "Profile found")
	public ResponseEntity<ProfileDTO> getProfile(@PathVariable long id)
	{ ...}
}

Exception Handling

Use custom exceptions with appropriate HTTP status codes.

Reactive WebClient Clients (UI Module)

@Component
public class ProfileClient
{
	private WebClient webClient;

	@EventListener
	public void init(StartupEvent event)
	{
		webClient = webClientBuilder.clone()
				.baseUrl(RemoteUtils.getControlUrl() + PROFILES_PATH)
				.build();
	}

	public Mono<Profile> findById(long id)
	{
		return webClient.get()
				.uri("/{id}", id)
				.retrieve()
				.bodyToMono(Profile.class);
	}
}

Configuration Classes

Use @Configuration for feature-specific beans. Keep @Bean methods small and focused.

Testing Services

See junit-testing skill for testing patterns with mocks.