Spring is the most popular framework for writing high performing and easily testable Java code. There are many Spring projects, covering everything from configuration to security, web apps to integration, and plenty more. Start with the Spring guides and learn even more at Spring.io.
Spring Boot API
Learn how to quickly develop a REST API from start to finish to build a microservice from scratch with this Spring Boot guide.
Spring Cloud Data Flow with MongoDB on Kubernetes
Integrate a Spring Cloud Data Flow app with a MongoDB service running on Kubernetes.