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 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.
A beginner-to-advanced guide to migrating off Undertow on Spring Boot 4: why it was dropped (Jakarta EE 11 / Servlet 6.1), the real Maven error and runtime NoSuchMethodError you get if you fight it, Tomcat 11 tuning, and a verified working Jetty 12.1 alternative — all tested on a real Spring Boot 4.1 app.
A beginner-to-advanced guide to Spring Framework 7's built-in API versioning: the version attribute, baseline versions, the supported-versions gotcha, RFC-compliant deprecation headers, client-side ApiVersionInserter, and testing — verified against a real running Spring Boot 4.1 app.
A beginner-to-advanced guide to Micrometer and Spring Boot 4's new spring-boot-starter-opentelemetry: what actually changed (it isn't "Micrometer 2"), the Observation API, context propagation gotchas, a runnable cardinality-explosion demo, and a full migration checklist.
Why 0.1 + 0.2 isn't 0.3, when double is fine, when BigDecimal is mandatory, and when fixed-point long is fastest. A beginner-to-advanced guide to number precision in Java — with runnable code, real output, a benchmark, rounding modes, MathContext, and a decision table.
A practical Spring Framework 6 to 7 migration guide covering the Jakarta EE 11 baseline, removed and deprecated APIs, AOT and GraalVM changes, BeanRegistrar and proxy lifecycle changes, JSpecify null safety, testing and security implications, an upgrade checklist, and an AI prompt to scan your project.