quarkus-patterns

SKILL.md

Quarkus Development Patterns

Quarkus 3.x architecture and API patterns for cloud-native, event-driven services with Apache Camel.

When to Activate

Building REST APIs with JAX-RS or RESTEasy Reactive

Structuring resource → service → repository layers

Implementing event-driven patterns with Apache Camel and RabbitMQ

Configuring Hibernate Panache, caching, or reactive streams

Adding validation, exception mapping, or pagination

Setting up profiles for dev/staging/production environments (YAML config)

Custom logging with LogContext and Logback/Logstash encoder

Working with CompletableFuture for async operations

Implementing conditional flow processing

Working with GraalVM native compilation

Service Layer with Multiple Dependencies
@Slf4j
@ApplicationScoped
@RequiredArgsConstructor
public class OrderProcessingService {

    private final OrderValidator orderValidator;
    private final EventService eventService;
    private final OrderRepository orderRepository;
    private final FulfillmentPublisher fulfillmentPublisher;
    private final AuditPublisher auditPublisher;

    @Transactional
    public OrderReceipt process(CreateOrderCommand command) {
        ValidationResult validation = orderValidator.validate(command);
        if (!validation.valid()) {
            eventService.createErrorEvent(command, "ORDER_REJECTED", validation.message());
            throw new WebApplicationException(validation.message(), Response.Status.BAD_REQUEST);
        }

        Order order = Order.from(command);
        orderRepository.persist(order);

        OrderReceipt receipt = OrderReceipt.from(order);
        fulfillmentPublisher.publishAsync(receipt);
        auditPublisher.publish("ORDER_ACCEPTED", receipt);
        eventService.createSuccessEvent(receipt, "ORDER_ACCEPTED");

        log.info("Processed order {}", order.id);
        return receipt;
    }
}

Key Patterns:

@RequiredArgsConstructor for constructor injection via Lombok

@Slf4j for Logback logging

@Transactional on service methods that write through Panache or repositories

Validate input before persistence or message publication

Event tracking for success/error scenarios

Async Camel message publishing

Custom Logging Context Pattern (Logback)

@ApplicationScoped
public class ProcessingService {

    public void processDocument(Document doc) {
        LogContext logContext = CustomLog.getCurrentContext();
        try (SafeAutoCloseable ignored = CustomLog.startScope(logContext)) {
            // Add context to all log statements
            logContext.put("documentId", doc.getId().toString());
            logContext.put("documentType", doc.getType());
            logContext.put("userId", SecurityContext.getUserId());

            log.info("Starting document processing");

            // All logs within this scope inherit the context
            processInternal(doc);

            log.info("Document processing completed");
        } catch (Exception e) {
            log.error("Document processing failed", e);
            throw e;
        }
    }
}

Logback Configuration (logback.xml):

<configuration>
    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <encoder class="net.logstash.logback.encoder.LogstashEncoder">
            <includeContext>true</includeContext>
            <includeMdc>true</includeMdc>
        </encoder>
    </appender>

    <logger name="com.example" level="INFO"/>
    <root level="WARN">
        <appender-ref ref="CONSOLE"/>
    </root>
</configuration>

Event Service Pattern

@Slf4j
@ApplicationScoped
@RequiredArgsConstructor
public class EventService {
    private final EventRepository eventRepository;
    private final ObjectMapper objectMapper;

    public void createSuccessEvent(Object payload, String eventType) {
        Objects.requireNonNull(payload, "Payload cannot be null");
        Event event = new Event();
        event.setType(eventType);
        event.setStatus(EventStatus.SUCCESS);
        event.setPayload(serializePayload(payload));
        event.setTimestamp(Instant.now());

        eventRepository.persist(event);
        log.info("Success event created: {}", eventType);
    }

    public void createErrorEvent(Object payload, String eventType, String errorMessage) {
        Objects.requireNonNull(payload, "Payload cannot be null");
        if (errorMessage == null || errorMessage.isBlank()) {
            throw new IllegalArgumentException("Error message cannot be blank");
        }
        Event event = new Event();
        event.setType(eventType);
        event.setStatus(EventStatus.ERROR);
        event.setErrorMessage(errorMessage);
        event.setPayload(serializePayload(payload));
        event.setTimestamp(Instant.now());

        eventRepository.persist(event);
        log.error("Error event created: {} - {}", eventType, errorMessage);
    }

    private String serializePayload(Object payload) {
        try {
            return objectMapper.writeValueAsString(payload);
        } catch (JsonProcessingException e) {
            throw new IllegalStateException("Failed to serialize event payload", e);
        }
    }
}

Camel Message Publishing (RabbitMQ)

@Slf4j
@ApplicationScoped
@RequiredArgsConstructor
public class BusinessRulesPublisher {
    private final ProducerTemplate producerTemplate;

    public void publishSync(BusinessRulesPayload payload) {
        producerTemplate.sendBody(
            "direct:business-rules-publisher",
            payload
        );
    }
}

Camel Route Configuration:

@ApplicationScoped
public class BusinessRulesRoute extends RouteBuilder {

    @ConfigProperty(name = "camel.rabbitmq.queue.business-rules")
    String businessRulesQueue;

    @ConfigProperty(name = "rabbitmq.host")
    String rabbitHost;

    @ConfigProperty(name = "rabbitmq.port")
    Integer rabbitPort;

    @Override
    public void configure() {
        from("direct:business-rules-publisher")
            .routeId("business-rules-publisher")
            .log("Publishing message to RabbitMQ: ${body}")
            .marshal().json(JsonLibrary.Jackson)
            .toF("spring-rabbitmq:%s?hostname=%s&portNumber=%d",
                businessRulesQueue, rabbitHost, rabbitPort);
    }
}

Camel Direct Routes (In-Memory)

@ApplicationScoped
public class DocumentProcessingRoute extends RouteBuilder {

    @Override
    public void configure() {
        // Error handling
        onException(ValidationException.class)
            .handled(true)
            .to("direct:validation-error-handler")
            .log("Validation error: ${exception.message}");

        // Main processing route
        from("direct:process-document")
            .routeId("document-processing")
            .log("Processing document: ${header.documentId}")
            .bean(DocumentValidator.class, "validate")
            .bean(DocumentTransformer.class, "transform")
            .choice()
                .when(header("documentType").isEqualTo("INVOICE"))
                    .to("direct:process-invoice")
                .when(header("documentType").isEqualTo("CREDIT_NOTE"))
                    .to("direct:process-credit-note")
                .otherwise()
                    .to("direct:process-generic")
            .end();

        from("direct:validation-error-handler")
            .bean(EventService.class, "createErrorEvent")
            .log("Validation error handled");
    }
}

Camel File Processing

@ApplicationScoped
public class FileMonitoringRoute extends RouteBuilder {

    @ConfigProperty(name = "file.input.directory")
    String inputDirectory;

    @ConfigProperty(name = "file.processed.directory")
    String processedDirectory;

    @ConfigProperty(name = "file.error.directory")
    String errorDirectory;

    @Override
    public void configure() {
        from("file:" + inputDirectory + "?move=" + processedDirectory +
             "&moveFailed=" + errorDirectory + "&delay=5000")
            .routeId("file-monitor")
            .log("Processing file: ${header.CamelFileName}")
            .to("direct:process-file");

        from("direct:process-file")
            .bean(OrderProcessingService.class, "processFile")
            .log("File processing completed");
    }
}

Camel Bean Invocation

@ApplicationScoped
public class InvoiceRoute extends RouteBuilder {

    @Override
    public void configure() {
        from("direct:invoice-validation")
            .bean(InvoiceFlowValidator.class, "validateFlowWithConfig")
            .log("Validation result: ${body}");

        from("direct:persist-and-publish")
            .bean(DocumentJobService.class, "createDocumentAndJobEntities")
            .bean(BusinessRulesPublisher.class, "publishAsync")
            .bean(EventService.class, "createSuccessEvent(${body}, 'PUBLISHED')");
    }
}

REST API Structure

@Path("/api/documents")
@Produces(MediaType.APPLICATION_JSON)
@Consumes(MediaType.APPLICATION_JSON)
@RequiredArgsConstructor
public class DocumentResource {
  private final DocumentService documentService;

  @GET
  public Response list(
      @QueryParam("page") @DefaultValue("0") int page,
      @QueryParam("size") @DefaultValue("20") int size) {
    List<Document> documents = documentService.list(page, size);
    return Response.ok(documents).build();
  }

  @POST
  public Response create(@Valid CreateDocumentRequest request, @Context UriInfo uriInfo) {
    Document document = documentService.create(request);
    URI location = uriInfo.getAbsolutePathBuilder()
        .path(String.valueOf(document.id))
        .build();
    return Response.created(location).entity(DocumentResponse.from(document)).build();
  }

  @GET
  @Path("/{id}")
  public Response getById(@PathParam("id") Long id) {
    return documentService.findById(id)
        .map(DocumentResponse::from)
        .map(Response::ok)
        .orElse(Response.status(Response.Status.NOT_FOUND))
        .build();
  }
}

Repository Pattern (Panache Repository)

@ApplicationScoped
public class DocumentRepository implements PanacheRepository<Document> {

  public List<Document> findByStatus(DocumentStatus status, int page, int size) {
    return find("status = ?1 order by createdAt desc", status)
        .page(page, size)
        .list();
  }

  public Optional<Document> findByReferenceNumber(String referenceNumber) {
    return find("referenceNumber", referenceNumber).firstResultOptional();
  }

  public long countByStatusAndDate(DocumentStatus status, LocalDate date) {
    return count("status = ?1 and createdAt >= ?2", status, date.atStartOfDay());
  }
}

Service Layer with Transactions

@ApplicationScoped
@RequiredArgsConstructor
public class DocumentService {
  private final DocumentRepository repo;
  private final EventService eventService;

  @Transactional
  public Document create(CreateDocumentRequest request) {
    Document document = new Document();
    document.setReferenceNumber(request.referenceNumber());
    document.setDescription(request.description());
    document.setStatus(DocumentStatus.PENDING);
    document.setCreatedAt(Instant.now());

    repo.persist(document);

    eventService.createSuccessEvent(document, "DOCUMENT_CREATED");

    return document;
  }

  public Optional<Document> findById(Long id) {
    return repo.findByIdOptional(id);
  }

  public List<Document> list(int page, int size) {
    return repo.findAll()
        .page(page, size)
        .list();
  }
}

DTOs and Validation

public record CreateDocumentRequest(
    @NotBlank @Size(max = 200) String referenceNumber,
    @NotBlank @Size(max = 2000) String description,
    @NotNull @FutureOrPresent Instant validUntil,
    @NotEmpty List<@NotBlank String> categories) {}

public record DocumentResponse(Long id, String referenceNumber, DocumentStatus status) {
  public static DocumentResponse from(Document document) {
    return new DocumentResponse(document.getId(), document.getReferenceNumber(),
        document.getStatus());
  }
}

Exception Mapping

@Provider
public class ValidationExceptionMapper implements ExceptionMapper<ConstraintViolationException> {
  @Override
  public Response toResponse(ConstraintViolationException exception) {
    String message = exception.getConstraintViolations().stream()
        .map(cv -> cv.getPropertyPath() + ": " + cv.getMessage())
        .collect(Collectors.joining(", "));

    return Response.status(Response.Status.BAD_REQUEST)
        .entity(Map.of("error", "validation_error", "message", message))
        .build();
  }
}

@Provider
@Slf4j
public class GenericExceptionMapper implements ExceptionMapper<Exception> {

  @Override
  public Response toResponse(Exception exception) {
    log.error("Unhandled exception", exception);
    return Response.status(Response.Status.INTERNAL_SERVER_ERROR)
        .entity(Map.of("error", "internal_error", "message", "An unexpected error occurred"))
        .build();
  }
}

CompletableFuture Async Operations

@Slf4j
@ApplicationScoped
@RequiredArgsConstructor
public class FileStorageService {
    private final S3Client s3Client;
    private final ExecutorService executorService;

    @ConfigProperty(name = "storage.bucket-name")
    String bucketName;

    public CompletableFuture<StoredDocumentInfo> uploadOriginalFile(
            InputStream inputStream,
            long size,
            LogContext logContext,
            InvoiceFormat format) {

        return CompletableFuture.supplyAsync(() -> {
            try (SafeAutoCloseable ignored = CustomLog.startScope(logContext)) {
                String path = generateStoragePath(format);

                PutObjectRequest request = PutObjectRequest.builder()
                    .bucket(bucketName)
                    .key(path)
                    .contentLength(size)
                    .build();

                s3Client.putObject(request, RequestBody.fromInputStream(inputStream, size));

                log.info("File uploaded to S3: {}", path);

                return new StoredDocumentInfo(path, size, Instant.now());
            } catch (Exception e) {
                log.error("Failed to upload file to S3", e);
                throw new StorageException("Upload failed", e);
            }
        }, executorService);
    }
}

Caching

@ApplicationScoped
@RequiredArgsConstructor
public class DocumentCacheService {
  private final DocumentRepository repo;

  @CacheResult(cacheName = "document-cache")
  public Optional<Document> getById(@CacheKey Long id) {
    return repo.findByIdOptional(id);
  }

  @CacheInvalidate(cacheName = "document-cache")
  public void evict(@CacheKey Long id) {}

  @CacheInvalidateAll(cacheName = "document-cache")
  public void evictAll() {}
}

Configuration as YAML

# application.yml
"%dev":
  quarkus:
    datasource:
      jdbc:
        url: jdbc:postgresql://localhost:5432/dev_db
      username: dev_user
      password: ${DB_PASSWORD}
    hibernate-orm:
      database:
        generation: drop-and-create

  rabbitmq:
    host: localhost
    port: 5672
    username: ${RABBITMQ_USER}
    password: ${RABBITMQ_PASSWORD}

"%test":
  quarkus:
    datasource:
      jdbc:
        url: jdbc:h2:mem:test
    hibernate-orm:
      database:
        generation: drop-and-create

"%prod":
  quarkus:
    datasource:
      jdbc:
        url: ${DATABASE_URL}
      username: ${DB_USER}
      password: ${DB_PASSWORD}
    hibernate-orm:
      database:
        generation: validate

  rabbitmq:
    host: ${RABBITMQ_HOST}
    port: ${RABBITMQ_PORT}
    username: ${RABBITMQ_USER}
    password: ${RABBITMQ_PASSWORD}

# Camel configuration
camel:
  rabbitmq:
    queue:
      business-rules: business-rules-queue
      invoice-processing: invoice-processing-queue

Health Checks

@Readiness
@ApplicationScoped
@RequiredArgsConstructor
public class DatabaseHealthCheck implements HealthCheck {
  private final AgroalDataSource dataSource;

  @Override
  public HealthCheckResponse call() {
    try (Connection conn = dataSource.getConnection()) {
      boolean valid = conn.isValid(2);
      return HealthCheckResponse.named("Database connection")
          .status(valid)
          .build();
    } catch (SQLException e) {
      return HealthCheckResponse.down("Database connection");
    }
  }
}

@Liveness
@ApplicationScoped
public class CamelHealthCheck implements HealthCheck {
  @Inject
  CamelContext camelContext;

  @Override
  public HealthCheckResponse call() {
    boolean isStarted = camelContext.getStatus().isStarted();
    return HealthCheckResponse.named("Camel Context")
        .status(isStarted)
        .build();
  }
}

Dependencies (Maven)

<properties>
    <quarkus.platform.version>3.27.0</quarkus.platform.version>
    <lombok.version>1.18.42</lombok.version>
    <assertj-core.version>3.24.2</assertj-core.version>
    <jacoco-maven-plugin.version>0.8.13</jacoco-maven-plugin.version>
    <maven.compiler.release>17</maven.compiler.release>
</properties>

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>io.quarkus.platform</groupId>
            <artifactId>quarkus-bom</artifactId>
            <version>${quarkus.platform.version}</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
        <dependency>
            <groupId>io.quarkus.platform</groupId>
            <artifactId>quarkus-camel-bom</artifactId>
            <version>${quarkus.platform.version}</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

<dependencies>
    <!-- Quarkus Core -->
    <dependency>
        <groupId>io.quarkus</groupId>
        <artifactId>quarkus-arc</artifactId>
    </dependency>
    <dependency>
        <groupId>io.quarkus</groupId>
        <artifactId>quarkus-config-yaml</artifactId>
    </dependency>

    <!-- Camel Extensions -->
    <dependency>
        <groupId>org.apache.camel.quarkus</groupId>
        <artifactId>camel-quarkus-spring-rabbitmq</artifactId>
    </dependency>
    <dependency>
        <groupId>org.apache.camel.quarkus</groupId>
        <artifactId>camel-quarkus-direct</artifactId>
    </dependency>
    <dependency>
        <groupId>org.apache.camel.quarkus</groupId>
        <artifactId>camel-quarkus-bean</artifactId>
    </dependency>

    <!-- Lombok -->
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <version>${lombok.version}</version>
        <scope>provided</scope>
    </dependency>

    <!-- Logging -->
    <dependency>
        <groupId>io.quarkiverse.logging.logback</groupId>
        <artifactId>quarkus-logging-logback</artifactId>
    </dependency>
    <dependency>
        <groupId>net.logstash.logback</groupId>
        <artifactId>logstash-logback-encoder</artifactId>
    </dependency>
</dependencies>

Best Practices

Architecture

Use @RequiredArgsConstructor with Lombok for constructor injection

Keep service layer thin; delegate complex logic to specialized classes

Use Camel routes for message routing and integration patterns

Prefer Panache Repository pattern for data access

Event-Driven

Always track operations with EventService (success/error events)

Use Camel direct: endpoints for in-memory routing

Use spring-rabbitmq component for RabbitMQ integration

Implement async publishing with ProducerTemplate.asyncSendBody()

Logging

Use Logback with Logstash encoder for structured logging

Propagate LogContext through service calls with SafeAutoCloseable

Add contextual information to LogContext for request tracing

Use @Slf4j instead of manual logger instantiation

Async Operations

Use CompletableFuture for non-blocking I/O operations

Call .join() when you need to wait for completion

Handle exceptions from CompletableFuture properly

Pass LogContext to async operations for tracing

Configuration

Use YAML configuration (quarkus-config-yaml)

Profile-aware configuration for dev/test/prod environments

Externalize sensitive configuration to environment variables

Use @ConfigProperty for type-safe config injection

Validation

Validate at resource layer with @Valid

Use Bean Validation annotations on DTOs

Map exceptions to proper HTTP responses with @Provider

Transactions

Use @Transactional on service methods that modify data

Keep transactions short and focused

Avoid calling async operations within transactions

Testing

Use camel-quarkus-junit5 for route testing

Use AssertJ for assertions

Mock all external dependencies

Test conditional flow logic thoroughly

Quarkus-Specific

Stay on latest LTS version (3.x)

Use Quarkus dev mode for hot reload

Add health checks for production readiness

Test native compilation compatibility periodically