Dedicated to sharing advanced Java technical insights, daily work snippets, and the power of persistent effort.
This article shares hands‑on production experience with Kafka, covering how to tune producer throughput, prevent message loss, control duplicate consumption, handle backlog, maintain ordering, understand rebalance, and explains why Kafka delivers such high performance.
This article explains the fundamentals of CORS, why browsers enforce the same‑origin policy, how Spring Boot detects and processes cross‑origin and preflight requests, and provides a minimal configuration and JavaScript example to resolve CORS issues in a Spring Boot application.
This article explains the fundamentals of MySQL master‑slave replication, detailing how binlog‑based data syncing works and providing a complete Docker‑based deployment guide—including configuration files, user creation, replication commands, and troubleshooting tips for a one‑master‑two‑slave cluster.
The article walks through a common database requirement—grouping rows, sorting within each group, and extracting the first (or top N) records—by preparing sample data, comparing MySQL window functions, subqueries, and JOIN solutions, adding index optimizations, and demonstrating equivalent Elasticsearch aggregations, all backed by concrete performance measurements.
This article explains why Spring cannot resolve circular dependencies when a bean method is annotated with @Async, detailing the underlying bean post‑processor mechanisms, the order of proxy creation, and practical solutions such as removing @Async, using @Lazy, or adjusting bean factory settings.
The article examines common pitfalls of Spring Boot scheduled tasks—such as missing logs, single‑threaded execution, and distributed conflicts—offers trace‑ID logging via AOP, discusses async handling, outlines multi‑threading and distributed scheduling options, and explains the inner workings of @Scheduled and cron expressions.
This article compares three single‑node scheduling approaches in Spring Boot—Java's legacy Timer, the modern ScheduledExecutorService, and Spring's @Scheduled annotation—showing their implementations, execution characteristics, thread handling, error behavior, and when to prefer each solution.
The article experimentally shows that MySQL's IN clause may use a range index, switch to a full‑table scan, or stay constant depending on the number of values, table size, and the range_optimizer_max_mem_size setting, providing concrete thresholds and configuration guidance.
The article explains how Java’s ternary operator can cause NullPointerException when type inference leads to automatic unboxing of a null wrapper, demonstrates this with concrete code examples, decompiled bytecode, and offers strategies such as using consistent types or replacing the ternary with if‑else.
This guide explains Elasticsearch's mapping concepts, compares dynamic and static mappings, and demonstrates how to choose between Array, Flattened, and Nested field types with concrete code examples, performance trade‑offs, and practical recommendations for real‑world business systems.
