java-coding-standards

// PASS: Favor records and final fields
public record MarketDto(Long id, String name, MarketStatus status) {}
 
public class Market {
  private final Long id;
  private final String name;
  // getters only, no setters
}
 
// PASS: [QUARKUS] Panache active-record entities use public fields (Quarkus convention)
@Entity
public class Market extends PanacheEntity {
  public String name;
  public MarketStatus status;
  // Panache generates accessors at build time; public fields are idiomatic here
}
 
// PASS: [QUARKUS] Panache MongoDB entities
@MongoEntity(collection = "markets")
public class Market extends PanacheMongoEntity {
  public String name;
  public MarketStatus status;
}

// PASS: Return Optional from find* methods
// [SPRING]
Optional<Market> market = marketRepository.findBySlug(slug);
 
// [QUARKUS] Panache
Optional<Market> market = Market.find("slug", slug).firstResultOptional();
 
// PASS: Map/flatMap instead of get()
return market
    .map(MarketResponse::from)
    .orElseThrow(() -> new EntityNotFoundException("Market not found"));

// PASS: Use streams for transformations, keep pipelines short
List<String> names = markets.stream()
    .map(Market::name)
    .filter(Objects::nonNull)
    .toList();
 
// FAIL: Avoid complex nested streams; prefer loops for clarity

// PASS: [SPRING] Constructor injection (preferred over @Autowired on fields)
@Service
public class MarketService {
  private final MarketRepository marketRepository;
 
  public MarketService(MarketRepository marketRepository) {
    this.marketRepository = marketRepository;
  }
}
 
// PASS: [QUARKUS] Constructor injection
@ApplicationScoped
public class MarketService {
  private final MarketRepository marketRepository;
 
  @Inject
  public MarketService(MarketRepository marketRepository) {
    this.marketRepository = marketRepository;
  }
}
 
// PASS: [QUARKUS] Package-private field injection (acceptable in Quarkus — avoids proxy issues)
@ApplicationScoped
public class MarketService {
  @Inject
  MarketRepository marketRepository;
}
 
// FAIL: [SPRING] Field injection with @Autowired
@Autowired
private MarketRepository marketRepository; // use constructor injection
 
// FAIL: [QUARKUS] @Singleton when interception or lazy init is needed
@Singleton // non-proxyable — use @ApplicationScoped instead
public class MarketService {}

// PASS: Return Uni/Multi from reactive endpoints
@GET
@Path("/{slug}")
public Uni<Market> findBySlug(@PathParam("slug") String slug) {
  return Market.find("slug", slug)
      .<Market>firstResult()
      .onItem().ifNull().failWith(() -> new MarketNotFoundException(slug));
}
 
// PASS: Non-blocking pipeline composition
public Uni<OrderConfirmation> placeOrder(OrderRequest req) {
  return validateOrder(req)
      .chain(valid -> persistOrder(valid))
      .chain(order -> notifyFulfillment(order));
}
 
// FAIL: Blocking call inside a Uni/Multi pipeline
public Uni<Market> find(String slug) {
  Market m = Market.find("slug", slug).firstResult(); // BLOCKING — breaks event loop
  return Uni.createFrom().item(m);
}
 
// FAIL: Subscribing more than once to a shared Uni
Uni<Market> shared = fetchMarket(slug);
shared.subscribe().with(m -> log(m));
shared.subscribe().with(m -> cache(m)); // double subscribe — use Uni.memoize()

throw new MarketNotFoundException(slug);

// [SPRING]
@RestControllerAdvice
public class GlobalExceptionHandler {
  @ExceptionHandler(MarketNotFoundException.class)
  public ResponseEntity<ErrorResponse> handle(MarketNotFoundException ex) {
    return ResponseEntity.status(404).body(ErrorResponse.from(ex));
  }
}
 
// [QUARKUS] Option A: ExceptionMapper
@Provider
public class MarketNotFoundMapper implements ExceptionMapper<MarketNotFoundException> {
  @Override
  public Response toResponse(MarketNotFoundException ex) {
    return Response.status(404).entity(ErrorResponse.from(ex)).build();
  }
}
 
// [QUARKUS] Option B: @ServerExceptionMapper (RESTEasy Reactive)
@ServerExceptionMapper
public RestResponse<ErrorResponse> handle(MarketNotFoundException ex) {
  return RestResponse.status(Status.NOT_FOUND, ErrorResponse.from(ex));
}

public <T extends Identifiable> Map<Long, T> indexById(Collection<T> items) { ... }

src/main/java/com/example/app/
  config/
  controller/
  service/
  repository/
  domain/
  dto/
  util/
src/main/resources/
  application.yml
src/test/java/... (mirrors main)

src/main/java/com/example/app/
  config/              # @ConfigMapping, @ConfigProperty beans, Producers
  resource/            # JAX-RS resources (not "controller")
  service/
  repository/          # PanacheRepository implementations (if not using active record)
  domain/              # JPA/Panache entities, MongoDB entities
  dto/
  util/
  mapper/              # MapStruct mappers (if used)
src/main/resources/
  application.properties   # Quarkus convention (YAML supported with quarkus-config-yaml)
  import.sql               # Hibernate auto-import for dev/test
src/test/java/... (mirrors main)

// [SPRING] SLF4J
private static final Logger log = LoggerFactory.getLogger(MarketService.class);
log.info("fetch_market slug={}", slug);
log.error("failed_fetch_market slug={}", slug, ex);
 
// [QUARKUS] JBoss Logging (default, zero-cost at build time)
private static final Logger log = Logger.getLogger(MarketService.class);
log.infof("fetch_market slug=%s", slug);
log.errorf(ex, "failed_fetch_market slug=%s", slug);
 
// [QUARKUS] Alternative: simplified logging with @Inject
@Inject
Logger log; // CDI-injected, scoped to declaring class

// [SPRING] @ConfigurationProperties
@ConfigurationProperties(prefix = "market")
public record MarketProperties(int maxPageSize, Duration cacheTtl) {}
 
// [QUARKUS] @ConfigMapping (type-safe, build-time validated)
@ConfigMapping(prefix = "market")
public interface MarketConfig {
  int maxPageSize();
  Duration cacheTtl();
}
 
// [QUARKUS] Simple values with @ConfigProperty
@ConfigProperty(name = "market.max-page-size", defaultValue = "100")
int maxPageSize;

// [SPRING] Controller test
@WebMvcTest(MarketController.class)
class MarketControllerTest {
  @Autowired MockMvc mockMvc;
  @MockBean MarketService marketService;
}
 
// [QUARKUS] Integration test
@QuarkusTest
class MarketResourceTest {
  @InjectMock
  MarketService marketService;
 
  @Test
  void should_return_404_when_market_not_found() {
    given().when().get("/markets/unknown").then().statusCode(404);
  }
}
 
// [QUARKUS] Unit test (no CDI, no @QuarkusTest)
@ExtendWith(MockitoExtension.class)
class MarketServiceTest {
  @Mock MarketRepository marketRepository;
  @InjectMocks MarketService marketService;
}