Start from zero. Finish with a real application.You need to know basic Java. That is genuinely all. Everything else - HTTP, Maven, SQL, Docker, testing - is explained the first time it appears, in plain words, with no assumed background.You will build one small application and grow it across fifteen chapters: a web API, then a real database, then caching, security, messaging, monitoring and deployment. By the end you will have written the kind of service that runs in production.What you will learnYour first project, and what the framework is really doing behind the annotationsREST APIs with validation, error handling and versioningSQL and NoSQL data access, with your queries written for youTesting at every level, against real databases in containersSecurity, messaging, metrics, tracing and native imagesAPI gateways, circuit breakers, and building your own Spring Boot starter Every listing was compiled and run against Spring Boot 4.1.1 on Java 25 before it was printed - with real PostgreSQL, MongoDB, Redis, RabbitMQ and Kafka. The log output, JSON responses and error messages in this book came from actual program runs, not from imagination.Version 4 renamed a great many things. If you have read older tutorials, some of what you remember is now wrong. This book teaches the new way from the first page.