affaan-m
Spring Boot architecture patterns, REST API design, layered services, data access, caching, async processing, and logging. Use for Java Spring Boot backend work.
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Spring Boot architecture and API patterns for scalable, production-grade services.
@RestController
@RequestMapping("/api/markets")
@Validated
class MarketController {
private final MarketService marketService;
MarketController(MarketService marketService) {
this.marketService = marketService;
}
@GetMapping
ResponseEntity<Page<MarketResponse>> list(
@RequestParam(defaultValue = "0") int page,
@RequestParam(defaultValue = "20") int size) {
Page<Market> markets = marketService.list(PageRequest.of(page, size));
return ResponseEntity.ok(markets.map(MarketResponse::from));
}
@PostMapping
ResponseEntity<MarketResponse> create(@Valid @RequestBody CreateMarketRequest request) {
Market market = marketService.create(request);
return ResponseEntity.status(HttpStatus.CREATED).body(MarketResponse.from(market));
}
}
public interface MarketRepository extends JpaRepository<MarketEntity, Long> {
@Query("select m from MarketEntity m where m.status = :status order by m.volume desc")
List<MarketEntity> findActive(@Param("status") MarketStatus status, Pageable pageable);
}
@Service
public class MarketService {
private final MarketRepository repo;
public MarketService(MarketRepository repo) {
this.repo = repo;
}
@Transactional
public Market create(CreateMarketRequest request) {
MarketEntity entity = MarketEntity.from(request);
MarketEntity saved = repo.save(entity);
return Market.from(saved);
}
}
public record CreateMarketRequest(
@NotBlank @Size(max = 200) String name,
@NotBlank @Size(max = 2000) String description,
@NotNull @FutureOrPresent Instant endDate,
@NotEmpty List<@NotBlank String> categories) {}
public record MarketResponse(Long id, String name, MarketStatus status) {
static MarketResponse from(Market market) {
return new MarketResponse(market.id(), market.name(), market.status());
}
}
@ControllerAdvice
class GlobalExceptionHandler {
@ExceptionHandler(MethodArgumentNotValidException.class)
ResponseEntity<ApiError> handleValidation(MethodArgumentNotValidException ex) {
String message = ex.getBindingResult().getFieldErrors().stream()
.map(e -> e.getField() + ": " + e.getDefaultMessage())
.collect(Collectors.joining(", "));
return ResponseEntity.badRequest().body(ApiError.validation(message));
}
@ExceptionHandler(AccessDeniedException.class)
ResponseEntity<ApiError> handleAccessDenied() {
return ResponseEntity.status(HttpStatus.FORBIDDEN).body(ApiError.of("Forbidden"));
}
@ExceptionHandler(Exception.class)
ResponseEntity<ApiError> handleGeneric(Exception ex) {
// Log unexpected errors with stack traces
return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR)
.body(ApiError.of("Internal server error"));
}
}
Requires @EnableCaching on a configuration class.
@Service
public class MarketCacheService {
private final MarketRepository repo;
public MarketCacheService(MarketRepository repo) {
this.repo = repo;
}
@Cacheable(value = "market", key = "#id")
public Market getById(Long id) {
return repo.findById(id)
.map(Market::from)
.orElseThrow(() -> new EntityNotFoundException("Market not found"));
}
@CacheEvict(value = "market", key = "#id")
public void evict(Long id) {}
}
Requires @EnableAsync on a configuration class.
@Service
public class NotificationService {
@Async
public CompletableFuture<Void> sendAsync(Notification notification) {
// send email/SMS
return CompletableFuture.completedFuture(null);
}
}
@Service
public class ReportService {
private static final Logger log = LoggerFactory.getLogger(ReportService.class);
public Report generate(Long marketId) {
log.info("generate_report marketId={}", marketId);
try {
// logic
} catch (Exception ex) {
log.error("generate_report_failed marketId={}", marketId, ex);
throw ex;
}
return new Report();
}
}
@Component
public class RequestLoggingFilter extends OncePerRequestFilter {
private static final Logger log = LoggerFactory.getLogger(RequestLoggingFilter.class);
@Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response,
FilterChain filterChain) throws ServletException, IOException {
long start = System.currentTimeMillis();
try {
filterChain.doFilter(request, response);
} finally {
long duration = System.currentTimeMillis() - start;
log.info("req method={} uri={} status={} durationMs={}",
request.getMethod(), request.getRequestURI(), response.getStatus(), duration);
}
}
}
PageRequest page = PageRequest.of(pageNumber, pageSize, Sort.by("createdAt").descending());
Page<Market> results = marketService.list(page);
public <T> T withRetry(Supplier<T> supplier, int maxRetries) {
int attempts = 0;
while (true) {
try {
return supplier.get();
} catch (Exception ex) {
attempts++;
if (attempts >= maxRetries) {
throw ex;
}
try {
Thread.sleep((long) Math.pow(2, attempts) * 100L);
} catch (InterruptedException ie) {
Thread.currentThread().interrupt();
throw ex;
}
}
}
}
Security Note: The X-Forwarded-For header is untrusted by default because clients can spoof it.
Only use forwarded headers when:
ForwardedHeaderFilter as a beanserver.forward-headers-strategy=NATIVE or FRAMEWORK in application propertiesX-Forwarded-For headerWhen ForwardedHeaderFilter is properly configured, request.getRemoteAddr() will automatically
return the correct client IP from the forwarded headers. Without this configuration, use
request.getRemoteAddr() directly—it returns the immediate connection IP, which is the only
trustworthy value.
@Component
public class RateLimitFilter extends OncePerRequestFilter {
private final Map<String, Bucket> buckets = new ConcurrentHashMap<>();
/*
* SECURITY: This filter uses request.getRemoteAddr() to identify clients for rate limiting.
*
* If your application is behind a reverse proxy (nginx, AWS ALB, etc.), you MUST configure
* Spring to handle forwarded headers properly for accurate client IP detection:
*
* 1. Set server.forward-headers-strategy=NATIVE (for cloud platforms) or FRAMEWORK in
* application.properties/yaml
* 2. If using FRAMEWORK strategy, register ForwardedHeaderFilter:
*
* @Bean
* ForwardedHeaderFilter forwardedHeaderFilter() {
* return new ForwardedHeaderFilter();
* }
*
* 3. Ensure your proxy overwrites (not appends) the X-Forwarded-For header to prevent spoofing
* 4. Configure server.tomcat.remoteip.trusted-proxies or equivalent for your container
*
* Without this configuration, request.getRemoteAddr() returns the proxy IP, not the client IP.
* Do NOT read X-Forwarded-For directly—it is trivially spoofable without trusted proxy handling.
*/
@Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response,
FilterChain filterChain) throws ServletException, IOException {
// Use getRemoteAddr() which returns the correct client IP when ForwardedHeaderFilter
// is configured, or the direct connection IP otherwise. Never trust X-Forwarded-For
// headers directly without proper proxy configuration.
String clientIp = request.getRemoteAddr();
Bucket bucket = buckets.computeIfAbsent(clientIp,
k -> Bucket.builder()
.addLimit(Bandwidth.classic(100, Refill.greedy(100, Duration.ofMinutes(1))))
.build());
if (bucket.tryConsume(1)) {
filterChain.doFilter(request, response);
} else {
response.setStatus(HttpStatus.TOO_MANY_REQUESTS.value());
}
}
}
Use Spring’s @Scheduled or integrate with queues (e.g., Kafka, SQS, RabbitMQ). Keep handlers idempotent and observable.
spring.mvc.problemdetails.enabled=true for RFC 7807 errors (Spring Boot 3+)@Transactional(readOnly = true) for queries@NonNull and Optional where appropriateRemember: Keep controllers thin, services focused, repositories simple, and errors handled centrally. Optimize for maintainability and testability.
Use when you need to run Flow type checking, or when seeing Flow type errors in React code.
Use when you want to validate changes before committing, or when you need to check all React contribution requirements.
Use when feature flag tests fail, flags need updating, understanding @gate pragmas, debugging channel-specific test failures, or adding new flags to React.
Use when you need to check feature flag states, compare channels, or debug why a feature behaves differently across release channels.