Pro Spring Boot 4 An Authoritative Guide with Best Practices (Felipe Gutierrez, DaShaun Carter)（Z-Library）

【One-Line Pitch】 A hands-on, project-driven tour of modern Spring Boot that takes you from a first REST API to reactive systems, AI agents, and custom starters. Best for Java developers who already know some Spring and want a single authoritative path through Spring Boot 4's new capabilities. 【Book Arc】 - **Opening (~0%–12%)**: Sets up the two running projects (Customer CRM and Management CRM) and walks through project structure, auto-configuration internals, externalized configuration, profiles, logging, AOP, and JSON customization — the "how the magic works" foundation. - **Early (~12%–35%)**: Moves into data and web layers — JdbcClient, Spring Data JDBC/JPA, transactions and concurrency, then reactive programming with Project Reactor, R2DBC, and functional endpoints. - **Middle (~35%–60%)**: Expands into production concerns: security (OAuth2/JWT, mTLS, SSL bundles), messaging, native images with GraalVM, and building intelligent applications with Spring AI (LLMs, RAG, vector stores, MCP tools, Spring Shell). - **Late (~60%–80%)**: Turns applications into platforms — packaging logic as a custom starter with `@Conditional`, `@Enable` patterns, AOP, and publishing to GitHub Packages — then surveys what's new in Spring Boot 4. - **Ending (~80%–100%)**: Excerpts do not cover the closing chapters in detail; the table of contents ends with the Spring Boot 4 "what's new" summary and appendices. 【Key Takeaways】 - **Two projects carry the whole book** (Opening): Customer CRM (Maven, annotation-based) and Management CRM (Gradle, reactive/functional) recur across chapters, so each new topic lands on familiar code rather than toy snippets. - **Understanding auto-configuration is the real unlock** (Opening): the book traces startup through `@SpringBootApplication`, `SpringApplication`, and `SpringApplicationBuilder`, then layers in type-safe properties, profiles, and logging — this is what separates "using" from "debugging" Spring Boot. - **Data access is taught as a decision, not a recipe** (Early): JdbcClient vs. JdbcTemplate, Spring Data JDBC vs. JPA, and declarative vs. programmatic transactions are compared with explicit "when to use" guidance, including isolation levels and race conditions. - **Reactive is presented honestly** (Early): Reactor's Mono/Flux, R2DBC, resilience, and caching are demonstrated in two case studies, and the chapter closes with a "To React or Not to React?" comparison rather than dogma. - **Security spans stateless to zero-trust** (Early): OAuth2/JWT flows, reactive filter chains, one-time tokens, OIDC routes, mTLS with SSL bundles, and OpenTelemetry-based security observability are all covered with test cases. - **AI integration is a first-class chapter** (Middle): Spring AI with local LLMs via Ollama, RAG backed by a vector store, tool calling including MCP, agentic database queries over R2DBC, and a Spring Shell client — a concrete blueprint for an AI-assisted CRM. - **Custom starters are the capstone skill** (Late): a six-step progression from migrating core logic to `@Conditional` configuration, `@Enable` annotations, AOP auditing, and publishing to GitHub Packages, ending with a consumer demo. - **Spring Boot 4 changes are catalogued** (Late): virtual threads, enhanced AOT, RestClient/RestTestClient, Spring Security 7 with simplified 2FA, Project CRaC, Docker Compose integration, Problem Details, and compile-time null-safety. 【Reading Tips】 - **Skim Chapter 1 if you're experienced** — the authors explicitly invite this — but read the auto-configuration internals chapter carefully; it pays off in every later chapter. - **Pick your data path deliberately**: if you're building reactive services, deep-read the R2DBC and functional-endpoint case studies; if you're on JPA, focus on the transaction and concurrency sections instead. - **Treat the AI and custom-starter chapters as a pair**: the starter chapter migrates the AI agent code, so reading them back-to-back shows how to productionize an experiment. - **Run both projects side by side** (Maven/annotation vs. Gradle/functional) — the contrast is the book's main teaching device, and the testing sections assume you've done it. - **Use the Spring Boot 4 "what's new" chapter as a checklist** against your existing codebase before adopting the upgrade. 【Coverage Limits】 This guide is based on stratified excerpts that are dense in the front and middle of the book (table of contents, Chapter 1 code, and chapter previews) but thin on the closing chapters; messaging, GraalVM native images, and the final appendices are only glimpsed through headings, so specifics there are not covered.