Java & Spring

You put an object into a HashSet, then ask if the set contains an equal object, and it says no. The culprit is almost always a broken equals and hashCode contract – the most common quiet bug in everyday Java.

A process dies with OutOfMemoryError and restarts, and it will happen again. Heap dump analysis tells you what filled the heap: how to capture the dump automatically at the moment of death, and how to read the dominator tree without drowning.

One page load fires 200 queries and nobody notices until production. The N+1 query problem hides behind clean-looking code. Here is how it happens, how to catch it, and the four fixes with their honest trade-offs.

Annotating every service method with @Transactional is cargo cult. It holds database connections longer than needed, hides the boundary that actually matters, and silently does nothing when called from inside the same class.

Java Flight Recorder ships in the JDK and profiles production JVMs at roughly 1% overhead. Learn custom event settings, JFR event streaming, jfr CLI triage, JDK Mission Control analysis, and how to gate performance regressions in CI.

Spring Data JDBC maps domain-driven aggregates to relational tables without lazy loading or dirty tracking. Learn aggregate roots, value objects, @MappedCollection, optimistic locking, and when JDBC beats JPA for clean boundaries.

A deep dive into Java 25 value classes: flat memory layouts, identity-free semantics, and microbenchmarks showing 3-5x speedups over records for hot domain types.

Complete guide to building modular monoliths with Spring Modulith including module design, event-driven patterns, and future microservices migration paths.

Complete guide to migrating Spring Boot applications to version 4 with virtual threads and structured concurrency for massive throughput improvements.