This document discusses developing microservices with Java using the Spring framework and applying Spring Security and OAuth2 for authentication and authorization. It begins with an introduction to microservice architecture and advantages over monolithic architecture. It then discusses various Java libraries that can be used to build microservices, focusing on the Spring Boot framework. The document creates a proof-of-concept inventory management application to demonstrate building microservices with Spring Boot and securing APIs with Spring Security and OAuth2. It describes authentication needs for both web and non-web backend services.