Spring Boot — convention-over-configuration framework for building Spring-based Java applications
Four ways to keep a password out of your Spring Boot code, each run for real on Boot 4.1.2: what happens when the secret is missing, how rotation behaves, and five ways the value leaks anyway.
A client times out and retries a payment. Build Stripe-style Idempotency-Key handling in Spring Boot 4.1 with a Redis store and a Postgres store, and see what each does with replays, changed bodies, concurrent duplicates, expiry and a crash.
A beginner-first walk through MapStruct on Spring Boot 4.1.2 with Java records as DTOs: how the generated mapper works, nested and collection mapping, null-value strategies, updating existing objects, and what @AfterMapping, @BeforeMapping and @ObjectFactory really do when the target is an immutable record. Every figure comes out of a companion project whose 19 tests write the transcripts, plus the compiler's own error messages and an honestly labelled, indicative comparison with hand-written code and Dozer. Includes surprises: @MappingTarget on a record compiles to an empty method, and JDK 23+ no longer runs a processor that is only on the classpath.
A servlet Filter, a HandlerInterceptor and an @Aspect all run code around a request, but not at the same point. A traced Spring Boot 4.1 app on Tomcat shows the real order, what each can see, and where each one silently fails.
One invoice built three ways in Spring Boot 4.1: OpenPDF 3.0.5, iText Core 9.8.0 (AGPL) and Flying Saucer 10.7.0 rendering a Thymeleaf template. Checks which one shapes Marathi and Hindi correctly (none by default), the OpenPDF switch that does, streaming vs buffered downloads, font subsetting and timings.
A Spring AI streaming chat UI with no React: ChatClient to a Flux of server-sent events, an htmx front end, per-session memory, a Stop button that really cancels the model call, and back-pressure, all measured against a stub OpenAI-compatible server (no real provider was run).
Map, List, record and POJO attributes as JSON columns in Hibernate 7.4: the DDL on PostgreSQL 18 and MySQL 8, native JSONB operators and the question-mark trap, HQL JSON functions, GIN and expression index plans on 50,000 rows, dirty checking, and Jackson 3 vs 2.
Point one Spring AI 2.0.2 OpenAiChatModel at Docker Model Runner and at Ollama by changing only base-url and the model name. Same GGUF model, same prompts: decode speed, time to first token, container memory and tool-call success, with transcripts. Measured on a CPU-only shared sandbox with the real docker/model-runner image; GPU and Docker Desktop paths were not measured and the post says so.
Export Excel from Spring Boot without running out of memory: XSSF vs SXSSF measured under a fixed heap (XSSF dies between 50,000 and 100,000 rows in 512 MB), 1,000,000 rows streamed with StreamingResponseBody under 64 MB, sheet rolling at 1,048,576 rows, temp-file cleanup, OpenCSV traps and a file LibreOffice will not open.
A Spring Batch 6 chunk step calls a Spring AI ChatClient for 100,000 generated support tickets. Resilience4j rate limiting and retry, skip-and-record for malformed JSON, a restart after kill -9 in a second JVM that ends byte-identical, and a per-chunk cost ledger, all run against a deterministic simulated model with every number taken from a committed transcript.