Micronaut Java Framework

Micronaut is a modern, JVM-based full-stack framework for building modular, easily testable microservice and serverless applications, designed to provide extremely fast startup and low memory consumption without compromising developer productivity. Developed by Object Computing Inc. (OCI) and led by Graeme Rocher (creator of Grails), Micronaut was first released in 2018. Key features: compile-time dependency injection: unlike Spring which uses reflection at runtime, Micronaut performs all DI, AOP proxying, and configuration binding at compile time via annotation processors, eliminating reflection overhead. Fast startup: applications start in under a second; GraalVM native images start in tens of milliseconds, ideal for serverless (AWS Lambda) and scale-to-zero. Low memory: as low as 17MB heap usage for simple applications. Cloud-native: built-in service discovery (Consul, Eureka, Kubernetes), distributed configuration, client-side load balancing, circuit breakers (Resilience4j), retry, and health checks. Non-blocking I/O built on Netty with HTTP/2 support. Declarative HTTP clients via @Client for type-safe inter-service communication. Reactive programming via Project Reactor, RxJava, and Mutiny. Micronaut Data for compile-time SQL repository generation. GORM for MongoDB and Neo4j. Testing: JUnit 5 and Spock with @MicronautTest for DI-injected tests. GraalVM native image support with automatic reflection and proxy configuration. Serverless support for AWS Lambda, Google Cloud Functions, and Azure Functions. Messaging with Kafka and RabbitMQ. Security with JWT, OAuth2, LDAP. Open source under Apache-2.0.