Posts

WebAssembly is not only compact bytecode in the spec—it is an execution model that pins guest modules to host boundaries. Running Wasm on the JVM forces trade-offs between attaching native runtimes versus pure bytecode hosting for distribution, observability, and fault isolation; Chicory, QuickJS4J, OPA Wasm, protobuf4j, Lumis4j, and related stacks illustrate one idea from many angles—wrapping existing C/Rust/JS assets in versioned artifacts exposed through Java APIs to Spring Gateway, build plugins, or CLIs.

Spring Boot and Kotlin interoperate maturely on the JVM; teams often introduce Kotlin first in src/test, applying extension functions, default parameters, type-safe DSLs, and assertion styles such as Kotest in integration tests and MockMvc scenarios to cut boilerplate and tighten failure messages. Meanwhile, Java builders, overloaded static helpers, and Project Reactor’s StepVerifier each carry their own cognitive cost; the article organizes common motivations by dependency layer, alignable public APIs, and semantic boundaries to watch (e.g. JVM type erasure, whether reactive verification truly completes subscription).

With Spring Boot 4 and Spring Framework 7, dependencies split into finer starters by capability; outbound HTTP clients can be isolated from server-side MVC. The same codebase can enable built-in API version negotiation in Spring MVC alongside Spring Data JDBC and RestClient / declarative @HttpExchange clients. Spring Security 7 emphasizes composable Customizer<HttpSecurity>, one-time token login, WebAuthn, and annotation-driven multi-factor authentication.

Before a large-scale Spring Boot migration, establish repeatable integration verification and a controlled dependency baseline; then advance in layers—Starter, auto-configuration troubleshooting, Spring context inside an external container, transitional Holder, beanification, Servlet annotation migration, and executable WAR. The article is organized by dependency and runtime layers, contrasts demo-style bootstrap paths with the reference manual’s recommended path, and where official docs do not spell out behavior (for example process lifecycle when only a non-web context starts), leaves engineering-level uncertainty explicit.

For engineers already shipping services on the JVM and web stacks, this article starts from a typical Spring Boot + Kotlin real-time interactive application, traces the data path from database signals through reactive SSE to the browser, and breaks human–agent collaboration into three verifiable layers: compile-and-test closure, versioned project memory (CLAUDE.md, rules, Skills), and Hooks plus MCP on the tool-call path. The second half covers gaps in tests and state machines caused by spec-less iteration, how structured clarification (Interview) writes navigation and security decisions into the specification, and how cross-cutting steps can be silently dropped in long conversations—with ideas for segmented execution.

A comprehensive analysis of JFR (Java Flight Recorder) configuration system, usage methods, and event collection mechanisms. Covers JFR configuration system (global configuration, recording level configuration, JFC configuration files), multiple usage methods (JVM parameters, jcmd commands, JDK API, JMX), jfr tool analysis, event type classification and configuration applicability, as well as core changes and best practices from JDK 11 to JDK 25.

In-depth guide on how to quickly locate Java heap OOM using JFR (JDK Flight Recorder) with practical methods and underlying principles, covering JFR event analysis for three typical OOM scenarios, including key events such as Allocation Requiring GC, ZAllocationStall, ObjectAllocationOutsideTLAB, and techniques for collecting and analyzing them.

In-depth analysis of JVM error handling and diagnostic parameter design principles, implementation mechanisms, and version evolution, covering Heap Dump, Java heap OOM handling, error logging, and other key parameters with source code analysis and best practices.

An exploration of JEP 502’s StableValue API, which addresses the fundamental trade-off between immutability and initialization flexibility in Java. This article covers the API design, core implementation details including double-checked locking patterns, memory semantics, and JIT optimization strategies using the @Stable annotation.

An in-depth exploration of modern API security practices, covering key exchange mechanisms for web and mobile clients, essential security headers implementation, and effective anti-bot protection strategies to safeguard your applications while maintaining excellent user experience.

A comprehensive guide exploring why enabling HeapDumpOnOutOfMemoryError can cause significant performance issues in production environments, which OutOfMemoryError types actually trigger heap dumps, and better alternatives like JFR for memory leak detection and automatic service restart strategies.

A comprehensive comparison of PostgreSQL and MySQL for OLTP scenarios, exploring their fundamental architectural differences in secondary index handling and MVCC implementation, with practical insights on when to choose each database.

Discover when GraalVM Native Image processes show up in jps and learn our battle-tested approach for choosing between GraalVM Native Image and JVM in production environments. We break down our strategy for Lambda-style tasks versus long-running microservices.

Learn how to develop and test high-performance API clients using WebClient, TestContainers, and toxicproxy. This comprehensive guide covers asynchronous request handling, isolated testing environments, and realistic failure simulation for robust microservice development.

A comprehensive deep-dive into JVM memory architecture covering heap memory, metaspace, thread stacks, and compressed object pointers. This technical analysis examines memory allocation processes, Native Memory Tracking, and provides practical examples using tools like jol, jhsdb, and JFR for understanding JVM memory management internals.

A deep dive into diagnosing and resolving a production JVM issue where applications would freeze during hourly log synchronization tasks. We explore safepoint analysis, JVM log output blocking, asynchronous logging implementation, and WebFlux optimization to achieve a complete solution.

An in-depth investigation into mysterious JVM safepoint delays after upgrading to Java 17 and implementing centralized log collection with AWS EFS. We discovered how file I/O blocking during log output can freeze entire JVM processes and solved it using async logging and proper WebFlux implementation.

A comprehensive exploration of pseudo-random number generators in Java, covering everything from basic Linear Congruential algorithms to advanced LXM implementations in Java 17. Learn about algorithm performance, security considerations, and how to choose the right random number generator for your specific use case.

A comprehensive guide to understanding why MySQL queries slow down over time in sharded environments, exploring the underlying causes of storage fragmentation and MVCC-related issues, and providing practical solutions using table rebuilding techniques with OPTIMIZE TABLE for maintaining optimal database performance.

A deep dive into Java Memory Model (JMM) from specification to implementation, covering memory barriers, CPU reordering, and Java 9+ VarHandle APIs. Learn about coherence, causality, consensus, and how volatile, final, and other synchronization mechanisms work under the hood with practical jcstress examples.