Spring Boot 4 promotes gRPC to a first-class starter. A beginner-to-advanced guide: all four call types, then the failures whose error messages point somewhere other than their cause — the 4 MB limit and which side enforces it, the absent default deadline, cancellation that never interrupts your thread, UNKNOWN statuses, and the in-process test transport that cannot enforce message size limits at all.
A beginner-to-advanced guide to exactly-once semantics with Spring Kafka on Spring Boot 4.1 — idempotent producers, transactions, and read-process-write. Verified against a live broker: the acks=1 setting that silently disables idempotence, the transaction markers that break offset arithmetic (but not consumer lag), the random transactional.id that defeats fencing entirely, the database boundary Kafka cannot cross, and what a transaction actually costs.
A beginner-to-advanced guide to Generational ZGC on JDK 25 — the first LTS where it is the only ZGC. Colored pointers, load and store barriers, and a measured comparison against G1: ZGC's p99.9 of 1.4 ms vs G1's 95.2 ms, 1.5 ms of total freeze time vs 1.14 s, plus the failure modes and throughput costs nobody charts — allocation stalls, disabled compressed oops, and the promotion crossover where ZGC wins throughput too.
The refined Specification API, AOT repository generation, and shared EntityManager wiring are the parts of the Spring Data JPA 3 to 4 migration that don't show up in a repository interface. Part 3 of the migration series covers DeleteSpecification/UpdateSpecification, JpaSort.unsafe, AOT knobs, and native-image implications.
Spring Data JPA 4 quietly moved derived queries off the Criteria API onto JPQL strings. Part 2 of the migration series covers the benchmark, getSingleResultOrNull, provider differences (with a real EclipseLink regression), the removed native-query parser, NULLS precedence, and which new JPQL functions are portable.
Part 1 of a 3-part Spring Data JPA 3 to 4 migration series. Covers the platform bump, the hibernate-jpamodelgen to hibernate-processor rename, repository interface compatibility, the JSpecify @NullMarked null-handling shift, and what genuinely doesn't change. Verified against Spring Boot 4.0.6 and Spring Data JPA 4.0.6.
A beginner-to-advanced guide to Java's Vector API (JEP 537, twelfth incubator in JDK 27). Start from what a CPU vector and SIMD actually are, see how HotSpot's C2 auto-vectorizes simple loops for free (with an experiment that proves it), learn when auto-vectorization silently gives up, then write real vector loops with species, the loopBound tail pattern, and masks for branchless control flow - including a JMH-measured 5.0x speedup on one masked-filter workload and 5.7x on a branchy brightness kernel, the exact machine those numbers came from, and a runnable companion repository.
A beginner-to-advanced guide to Java value classes (JEP 401), Project Valhalla's first preview targeting JDK 28. Learn what object identity costs (with runnable benchmarks), the value keyword, value records, the new construction rule, changed == semantics, Objects.hasIdentity, scalarization and heap flattening (with diagrams and a real 3x LocalDate benchmark), migrated JDK classes, migration rules, and what's not in the preview yet.
A beginner-to-advanced guide to migrating the repository layer from Spring Data JPA 3 to 4 on Spring Boot 4.1: the hibernate-jpamodelgen → hibernate-processor coordinate swap and the silent metamodel failure it causes, why derived queries now generate JPQL instead of CriteriaQuery (and the getSingleResultOrNull edge case), records as @Embeddable value objects and projection targets, JSpecify nullability, the refined Specification API, and the removed config that breaks your build — all mapped to real code and errors on a Spring Boot 4.1 app.
Beginner-to-advanced guide to JSpecify null-safety in Spring Framework 7 / Spring Boot 4: the @Nullable/@NonNull migration, Kotlin interop, and a real NullAway build failure caught and fixed on a live Maven project.