networknt/light-4j

Light-4j is a Java framework for building microservices, designed to be much faster and lighter on memory than more common Java web frameworks like Spring Boot. The name stands for lightweight, and the project claims to be 44 times faster than Spring Boot with Tomcat and use one-fifth the memory, with benchmark links provided for verification. It was created by a developer who had worked on Java enterprise applications since the early 2000s and found existing options too heavy for modern cloud deployment. The framework is built around a plugin architecture where cross-cutting concerns, things like security, validation, logging, and rate limiting, are handled at the framework level rather than inside your application code. This means you write business logic and the framework automatically handles OAuth2 token verification, request validation against an API specification file, metrics collection, error handling, cross-site scripting protection, and service discovery. These features are wired together through middleware components rather than requiring you to import and configure separate libraries for each concern. There are several specialized sub-frameworks built on top of light-4j. One targets standard REST APIs defined with OpenAPI specifications, another handles GraphQL services, a third targets event-driven architectures using Kafka, and a fourth supports a hybrid approach mixing microservices and monolithic patterns. A code generator can scaffold a working project from an OpenAPI spec file, producing starter code, tests, and Docker configuration files ready for continuous deployment. Getting started involves either using the code generator or copying one of the example projects from a companion repository. The server runs as a plain Java application, which means you can debug it directly in an IDE without a container setup. Production deployments typically use Docker. The project is actively maintained and used in production at multiple companies, with documentation available on the project website.