Introduction to the URL‑Shortener Advent Calendar 2025
December 2025 is all about a project that has grown steadily in recent months: the Java-based URL Shortener, an open-source project implemented entirely with Core Java, Jetty, and Vaadin Flow. The Advent calendar accompanies users every day with a new feature, a technical deep dive, or an architectural improvement – from the basic data structure and REST handlers to UI components and security aspects.