---name: java-quarkus-developmentdescription: Java Quarkus development guidelines for building cloud-native applications with fast startup, minimal memory footprint, and GraalVM native builds---

Java Quarkus Development Best Practices

Core Principles

• Write clean, efficient, and well-documented Java code using Quarkus best practices
• Focus on fast startup and minimal memory footprint via GraalVM native builds
• Leverage Quarkus extensions for common functionality
• Design for containerized and serverless deployments
• Follow SOLID principles and microservices architecture patterns

Development Workflow

Quarkus Dev Mode

• Use quarkus dev for rapid iteration with live reload
• Leverage continuous testing during development
• Use Dev UI for debugging and configuration inspection
• Take advantage of Dev Services for local development

Configuration

Type-Safe Configuration

• Use @ConfigProperty for type-safe configuration injection
• Group related configs with @ConfigMapping interfaces
• Validate configuration at startup
• Document configuration properties

Profile-Based Configuration

• Use %dev, %test, %prod prefixes for environment-specific configs
• Override configs via environment variables in production
• Keep sensitive values out of source control
• Use .env files for local development

Dependency Injection

CDI Annotations

• Use @Inject for dependency injection
• Use @Named to qualify implementations
• Use @Singleton, @ApplicationScoped, @RequestScoped appropriately
• Prefer constructor injection for required dependencies

Bean Discovery

• Understand Quarkus build-time bean discovery
• Use @IfBuildProfile for conditional beans
• Avoid reflection-heavy patterns for native builds

REST API Development

RESTEasy Reactive

• Use @Path, @GET, @POST, etc. for endpoint definitions
• Return proper HTTP status codes
• Use @Valid for input validation
• Implement exception mappers for consistent error responses

Reactive Patterns

• Use Mutiny for reactive programming
• Leverage Uni and Multi for async operations
• Combine reactive with imperative code where appropriate

Data Access

Hibernate ORM with Panache

• Use Panache for simplified JPA patterns
• Leverage Active Record or Repository patterns
• Use PanacheEntity for entities with built-in operations
• Implement custom queries with find and list methods

Database Operations

• Use Flyway or Liquibase for migrations
• Configure connection pooling with Agroal
• Use reactive database clients for non-blocking I/O

Testing

JUnit 5 Integration

• Use @QuarkusTest for integration tests
• Use @QuarkusIntegrationTest for native image tests
• Leverage test profiles for different configurations

REST Endpoint Testing

• Use rest-assured for endpoint testing
• Test both success and error scenarios
• Verify response bodies and status codes
• Test authentication and authorization

Performance Optimization

Native Image Optimization

• Build native images with GraalVM for production
• Test native builds regularly during development
• Use @RegisterForReflection when needed
• Minimize reflection usage

Memory and Startup

• Monitor memory usage in containers
• Optimize for serverless cold starts
• Use lazy initialization where appropriate

Observability

Health Checks

• Use MicroProfile Health for liveness and readiness probes
• Implement custom health checks for dependencies
• Configure Kubernetes probes based on health endpoints

Metrics

• Use MicroProfile Metrics for application metrics
• Export metrics in Prometheus format
• Add custom metrics for business operations

Distributed Tracing

• Use OpenTracing/OpenTelemetry integration
• Propagate trace context across services
• Configure sampling appropriately for production

Security

• Use Quarkus Security extensions
• Implement authentication with OIDC or JWT
• Configure CORS for web clients
• Validate and sanitize all inputs
• Use HTTPS in production

Containerization

• Use Quarkus container image extensions
• Build multi-stage Dockerfiles for native images
• Configure resource limits appropriately
• Use distroless or minimal base images