War

Before a large-scale Spring Boot migration, establish repeatable integration verification and a controlled dependency baseline; then advance in layers—Starter, auto-configuration troubleshooting, Spring context inside an external container, transitional Holder, beanification, Servlet annotation migration, and executable WAR. The article is organized by dependency and runtime layers, contrasts demo-style bootstrap paths with the reference manual’s recommended path, and where official docs do not spell out behavior (for example process lifecycle when only a non-web context starts), leaves engineering-level uncertainty explicit.