This article explains how to design a clean, maintainable Spring MVC controller layer by unifying response structures, applying centralized exception handling, and leveraging JSR‑303 validation with custom rules, illustrated with comprehensive code examples and best‑practice guidelines.
This article explains LeetCode problem 124, describing the definition of a path in a binary tree, analyzing the constraints, and providing a detailed Java implementation that uses depth‑first search to compute the maximum path sum while handling negative sub‑paths.
This article demonstrates why @Transactional fails in multithreaded Spring services, presents a thread‑pool based solution using manual SqlSession control to achieve full rollback across child threads, and provides complete code examples and test results illustrating both failure and successful transaction handling.
The article explains that Java’s Random class uses a predictable linear‑congruential generator, making its output vulnerable to seed‑guessing attacks, and demonstrates how SecureRandom with strategies like SHA1PRNG, NativePRNGBlocking, and NativePRNGNonBlocking provides stronger, non‑predictable randomness suitable for security‑critical applications.
This article reviews the most important new features introduced in Java JDK 10 through JDK 21—including local‑variable type inference, the standardized HTTP client, experimental garbage collectors, pattern‑matching enhancements, records, sealed classes, and virtual threads—providing code examples and migration guidance for developers.
This article explains how to construct and send Ethereum JSON‑RPC calls such as net_version through a WebSocket connection using the Web3j Java library, including source code analysis, request construction, and a practical example with console output.
This article explains why iterating a Java HashMap with keySet() results in two traversals, detailing the internal iterator creation, the role of KeyIterator and HashIterator classes, and how the do‑while loop in HashIterator’s constructor locates the first entry, with code examples and bytecode analysis.
This article explains how to handle enum and JSON string parameters in Spring MVC by creating custom annotations and argument resolvers, demonstrates the implementation steps with full code examples, and also reviews Spring MVC's built‑in parameter binding mechanisms such as @RequestParam, @PathVariable, @RequestBody, and @ModelAttribute.
This article explains how to redesign a JSON payload that repeats a sessionId for each scene by moving the sessionId to the outer level and using MyBatis resultMap with a collection to map a Session object containing a list of Scene objects, including Java entity definitions, mapper XML, service, and controller code.
This article explains what unit testing is, why it is essential for software quality, outlines its benefits such as early bug detection and design improvement, and provides practical guidance on writing effective Java unit tests using JUnit5, Mockito, and JaCoCo, along with CI integration and best‑practice principles.
This article explains the concept and inner workings of Spring Boot Starters, demonstrates how they simplify dependency management and auto‑configuration, and provides a step‑by‑step guide to creating and using a custom Starter with full code examples.
This article presents a comprehensive collection of 28 practical IntelliJ IDEA shortcuts and configuration tricks—such as viewing local history, adjusting VM memory, adopting Eclipse keymaps, managing inspections, customizing templates, navigating code, and leveraging plugins—to dramatically improve Java development productivity.
The article reviews five major distributed unique ID generation methods—including UUID, Redis auto‑increment, database auto‑increment, database segment mode, and Snowflake—explains their principles, advantages, drawbacks, and provides practical integration guides and code examples for Java developers.
This article explains how to implement a flexible business retry mechanism in Spring using custom annotations and AOP, covering the rationale, code examples for the @Retry annotation, RetryAspect, transaction considerations, and alternative Spring Retry library integration.
This article explains the G1 garbage collector’s heap layout, collection cycles, pause prediction, log analysis, and monitoring tools, helping Java developers diagnose and resolve performance issues such as frequent restarts, OOM, CPU spikes, and periodic latency spikes.
This article explains Java compilation and decompilation basics, introduces the JD‑GUI decompiler, and provides a step‑by‑step guide to protect Java applications by configuring ProGuard and integrating it into a Maven build, including sample configuration files and common pitfalls.
Thread profiling uses threshold‑triggered tasks on business threads to capture stack snapshots, which a dedicated profiler thread sends via high‑performance gRPC to a server that queues them in Kafka, enriches and stores them in ClickHouse, correlates with OpenTelemetry traces, and provides metrics that let developers quickly pinpoint latency bottlenecks and improve system stability.
This article examines the benefits of moving from JDK 11 to the long‑term support JDK 17, detailing performance gains—especially sub‑millisecond ZGC pause times—new language features, compatibility considerations, benchmark results, and step‑by‑step migration instructions for Spring‑based applications.
The article investigates frequent OutOfMemoryError incidents in a distributed Java service, explains heap and metaspace causes, analyzes MyBatis source that retains large SQL strings in memory, reproduces the issue with heavy IN clauses and limited heap, and offers practical mitigation advice.
This article explains how Apache Pulsar is used within Apache InLong to collect, sort, and reliably deliver massive MySQL binlog incremental data, covering component architecture, job isolation, client and producer management, consumption strategies, common pitfalls, performance tuning, and practical code examples.
This article introduces the open‑source Disruptor framework, explains its core concepts such as Ring Buffer, Sequencer, and Wait Strategies, and provides a step‑by‑step Java demo—including Maven setup, event factory, handlers, and a test case—to illustrate building a high‑throughput, low‑latency in‑memory message queue.
This article compares Spring Boot and Quarkus across startup time, memory usage, CPU consumption, and response latency, presents benchmark results from JMeter and VisualVM tests, and provides practical guidance for migrating Java developers from Spring to the cloud‑native Quarkus framework.
This article explains the internal workings of HashMap traversal in Java, showing why using keySet() results in two passes—first converting to an iterator and then fetching values—and details the underlying iterator, KeyIterator, and HashIterator implementations with code examples.
This article details the design and implementation of a Java‑based flash‑sale (Seckill) system using SpringBoot, Redis, RabbitMQ, and related technologies, covering architecture, security, caching, asynchronous processing, oversell prevention, and rate‑limiting techniques.
This article explains the distinct origins, injection strategies, and internal processing of Spring's @Resource and @Autowired annotations, compares their behavior, and walks through relevant source code to illustrate how each annotation resolves dependencies.
November 2023’s TIOBE Index reveals Python still leads at 14.16%, while C# jumps to fifth place, narrowing its gap with Java to just 0.7%, as Java slips to fourth with its biggest monthly decline, and C and C++ also see modest drops.
This comprehensive guide explains Java's collection framework, covering the core interfaces Collection, List, Set, and Map, their abstract and concrete implementations, iterator mechanisms, and key differences that are essential for both interview preparation and real‑world backend development.
This article introduces Hutool, a comprehensive Java utility library that consolidates common functions such as file handling, encryption, date manipulation, and more, explains its key modules, shows how to add it via Maven, and provides practical code examples for utilities like DateUtil, StrUtil, NumberUtil, and SecureUtil.
This article explains how duplicate form submissions occur, outlines common prevention techniques such as token validation and timestamp checks, and demonstrates a practical SpringMVC interceptor implementation with token storage and scheduled cleanup to ensure request uniqueness and reduce server load.
This article explains why Java's BigDecimal is essential for high‑precision arithmetic, outlines common use cases such as finance and scientific computing, highlights typical pitfalls with floating‑point numbers, and provides practical code examples and best‑practice tips for correct usage.
Given a circular road with n stations and the distances between each consecutive pair, this article explains how to determine the minimal travel distance between any two stations by evaluating both clockwise and counter‑clockwise routes, providing problem details, examples, solution logic, reference implementations in Python, Java, and C++, and complexity analysis.
This article explains why iterating a Java HashMap via keySet() incurs two passes—once to obtain an iterator and again to fetch values—while entrySet() or Map.forEach() performs a single pass, detailing the underlying iterator implementations and their bytecode behavior.
This article explains why load balancing is crucial for RocketMQ producers, details the internal selection algorithm using ThreadLocal indexes and round‑robin logic, and provides Java code examples illustrating how messages are distributed across queues.
This article explains the Chain of Responsibility design pattern and demonstrates how to apply it in a Java backend to evaluate login risk factors such as password errors, unusual login times, IP whitelist violations, and abnormal login locations, providing full code examples and execution flow.
This article explains the definition and properties of directed acyclic graphs (DAG), describes the basic topological sorting algorithm steps, and provides a complete Java implementation using Guava's MutableGraph class, illustrating the process with an example and its execution result.
This article compares Java classes with Go structs, covering how each language handles state and behavior, inheritance versus composition, and visibility rules, while providing concrete code examples to illustrate the practical differences for developers.
This article introduces LiteFlow, a lightweight and fast component‑based rule engine that decouples complex business logic, explains its design principles, demonstrates usage in both non‑Spring and SpringBoot environments with Maven dependencies and XML configurations, and delves into its core components and execution flow through detailed source code analysis.
This article explains the concept of request merging for high‑concurrency web services, outlines its advantages and drawbacks, and provides a complete Java implementation using ScheduledExecutorService, a memory queue, and a generic BatchCollapser utility with usage examples.
This article explains the internal mechanics of Java's HashMap traversal, showing that keySet() incurs two passes due to iterator creation while entrySet() (or Map.forEach) iterates in a single pass, and it demonstrates the process through decompiled source code and concrete examples.
This article explains the concept of a local message table, shows how it can be used to achieve reliable distributed transaction consistency with MQ, and provides complete MySQL DDL and Java service code along with a retry mechanism and analysis of failure scenarios.
This article examines the causes of Java OutOfMemoryError in a distributed backend service, analyzes MyBatis-related memory leaks, demonstrates a reproducible scenario with large SQL concatenations and multithreading, and offers practical mitigation strategies to prevent heap and metaspace overflow.
This step‑by‑step guide shows how to download, configure, and launch SkyWalking with Spring Boot, connect it to Elasticsearch, instrument a sample service and Redis calls, and view real‑time monitoring data through the SkyWalking UI and Kibana.
The article analyzes why a Java API endpoint took eight seconds, demonstrates through benchmarks that List.sort() outperforms Stream.sorted(), shows how sorting on computed columns and using BigDecimal can drastically slow execution, and presents three practical optimizations that reduce the response time to under a second.
This article introduces a generic asynchronous processing SDK for Java back‑ends, explaining its purpose, advantages, underlying principles, components, design patterns, database schema, configuration, usage, and operational considerations, and provides complete code and configuration examples.
This article introduces the open‑source mall project—a SpringBoot + Vue + uni‑app e‑commerce platform with over 60 K GitHub stars—detailing its payment flow, architecture, tech stack, video tutorial series, and how to join the learning community for hands‑on development experience.
This article compares Spring Boot and Quarkus, detailing their architectures, performance benchmarks—including startup time, memory usage, CPU, and response latency—both in JVM and native modes, and provides guidance on migrating Spring applications to Quarkus with code examples and best‑practice tips.
This article explains the internal mechanics of HashMap traversal in Java, showing that keySet() uses an iterator that iterates twice to locate entries, whereas entrySet() (or Map.forEach) iterates only once, and it walks through the relevant source code and decompiled bytecode to illustrate the process.
This article explains why Elasticsearch is fast, outlines its key features, and provides a complete Spring Boot 2.4 tutorial—including dependencies, configuration, data model, repository usage, and test code—for building a distributed search service.
This guide demonstrates essential Java Stream API techniques—including grouping collections into maps, extracting first entries, performing reductions to find max or min, converting streams to lists, sorting, removing duplicates, and a comprehensive list of frequently used stream operations—providing practical code examples for Java 11 and 17.
This article explains why a Spring Boot application runs with the configured port when packaged as a JAR using the embedded Tomcat, but switches to Tomcat's default port and context path when deployed as a WAR, and provides step‑by‑step instructions to package and deploy both formats along with historical context and technical differences.
This article explains the business scenarios that drive the need for globally unique distributed IDs, analyzes the challenges of uniqueness, performance, and availability, and details Vivo's self‑built LuBan ID service—including its architecture, three ID formats, custom extensions, SDK usage, performance optimizations, and real‑world deployment metrics.
This article explains the concept of open interfaces and signature verification, outlines the end‑to‑end signing and verification flow, and provides a complete Spring Boot implementation including configuration properties, a signature manager, custom annotation, AOP aspect, request‑caching filter and utility classes, all illustrated with code snippets.
This article explains how to replace repetitive try‑catch blocks in Spring applications with a clean, assertion‑based approach combined with @ControllerAdvice and enum‑driven error codes, providing a unified way to handle service‑layer, controller‑layer, and unknown exceptions while keeping responses consistent and internationalized.
This guide presents 28 practical IntelliJ IDEA tips—from viewing code history and adjusting memory settings to customizing shortcuts, using useful plugins, and managing Maven dependencies—helping Java developers streamline their workflow and dramatically increase coding efficiency.
This article explains Huolala’s multi‑group microservice architecture, covering its background, core principles, deployment, discovery, routing strategies, extension mechanisms, and practical application scenarios that enable flexible, versioned, and policy‑driven service routing.
This article explains how the OpenAPI specification standardizes interfaces and improves security by using AppId/AppSecret pairs, RSA‑based signatures, timestamp and nonce mechanisms, parameter validation, rate limiting, and encryption best practices, accompanied by complete Java code examples.
Faced with a client demanding 500 requests per second, I discovered my Java backend only handled 50 /s due to slow SQL, excessive logging, thread‑pool misconfiguration, and costly Spring bean creation; by adding latency alerts, async execution, reducing thread counts, and fixing Redis bean scope, throughput nearly doubled.
This article explains RocketMQ's core components, the differences between push and pull consumption modes, and how the framework implements a pseudo‑push mechanism using long polling, including detailed code analysis of the consumer and broker side processes.
This guide explains how Java applications can send SMS messages efficiently by comparing client‑side SDK integration with a dedicated server‑side SMS platform, covering provider choices, code examples, multi‑channel aggregation with SMS4J, and design considerations for high‑availability messaging.
This guide explains why frequent garbage collection and heap memory overflow occur in Java applications, demonstrates how to reproduce the issue with a sample program, and walks through various techniques—including jmap histograms, heap dumps, VisualVM analysis, and remote JMX monitoring—to diagnose and resolve out‑of‑memory errors.
This article explains the challenges of data permission control in multi‑system environments, outlines a unified RBAC‑based model with extensible dimensions, and provides a step‑by‑step integration guide and SDK implementation for Java backends, including code snippets and practical considerations.
This article explains the common Java OutOfMemoryError types—including heap space, GC overhead limit exceeded, Metaspace, CodeCache, Direct Memory, and Linux OOM Killer—detailing their causes, symptoms, and step‑by‑step troubleshooting techniques for backend developers.
This article reviews the most widely adopted Java language enhancements introduced after Java 8, covering features such as local variable type inference, switch expressions, text blocks, records, pattern matching for instanceof, sealed classes, and improved NullPointerException messages, helping developers decide which upgrades to adopt.
This article compares the Spring Boot and Quarkus Java frameworks by examining their architectures, running reactive test applications, measuring startup time, memory usage, CPU consumption and response latency for both JVM and native builds, and provides practical guidance for migrating Spring developers to Quarkus.
This article explains the various Java OutOfMemoryError types—including Java heap space, GC overhead limit exceeded, Metaspace, CodeCache, Direct Memory, and Linux OOM Killer—describes their causes, typical symptoms, and provides step‑by‑step troubleshooting and mitigation strategies for developers.
This article walks through the design and implementation of a Java SpringBoot‑based electronic signature and seal system, covering the underlying concepts of digital signatures, the complete project structure, key controller and service code, utility classes, deployment steps, and a step‑by‑step functional demo with screenshots.
This article introduces TLog, a zero‑intrusion Java logging library that adds globally unique trace IDs, SpanId and upstream/downstream tags to microservice logs, outlines its key features, multiple integration modes, configuration examples for Log4j and async logging, and shows how to use it with Spring Boot, Spring Native and task frameworks like XXL‑JOB.
This document presents a series of real‑world examples showing how ChatGPT can assist cloud‑trading developers with backend tasks such as resource scheduling, regex interpretation, CSV generation, JavaBean‑to‑JSON conversion, Spring IoC learning, JSON formatting, Java 8 stream processing, and CI pipeline error analysis.
This article explains why traditional local locks fail in distributed systems, surveys common distributed‑lock approaches, and provides a step‑by‑step guide to building a robust Redis‑based lock in Java—including expiration handling, UUID safety, Lua‑script atomicity, re‑entrancy, automatic renewal, and the RedLock algorithm—while comparing its performance against plain local locks.
Given a circular road with n stations and the clockwise distances between consecutive stations, this article explains how to calculate the minimum travel distance between any two stations by comparing clockwise and counter‑clockwise routes, with full Python, Java, and C++ implementations.
Although many developers avoid using thread pools in business code, this article explains how thread pools already exist in web containers and RPC frameworks, why inserting custom pools can backfire, and when proper tuning or message queues are the better solution for improving throughput.
This article explains the internal structure of ThreadLocal, identifies scenarios where ThreadLocal can cause memory leaks—especially in thread‑pool environments—analyzes the root causes, and provides practical techniques such as using remove() and expungeStaleEntry() to avoid these leaks.
This article presents a curated list of essential Java libraries—including JUnit, Mockito, Jackson, Gson, SLF4J, Log4j2, Apache Commons, Guava, JAXB, Xerces, Apache POI, JavaAssist, Cglib, Eclipse Collections, Trove, Jsoup, Apache MINA, Netty, Lombok, and Testcontainers—explaining their purposes and why senior developers should master them.
This guide explains Spring Validation in Spring Boot 2.6, covering its lightweight features, configuration of Bean Validation providers, injection of validators, practical examples, custom annotation creation, method‑level validation, and additional configuration options with clear code samples.
This article provides a comprehensive, step‑by‑step analysis of MyBatis’s overall architecture, covering its core features, three‑layer design, configuration parsing, proxy generation, SQL execution process, and the underlying components that enable seamless Java‑to‑SQL mapping.
This article explains the core principles and multiple usage patterns of MyBatis PageHelper for pagination, demonstrates code examples, details its internal ThreadLocal and interceptor mechanisms, and highlights common pitfalls with safe versus unsafe practices to ensure reliable data retrieval.
This article explains core object‑oriented concepts such as encapsulation, abstraction, inheritance and polymorphism, then details common design principles and a wide range of design patterns—including factory, builder, bridge, singleton, strategy, adapter, and proxy—illustrated with complete Java code examples and usage guidelines.
This guide explains how Spring Cloud abstracts multiple circuit‑breaker implementations, shows synchronous and reactive usage with code examples, and demonstrates custom configuration of Resilience4J circuit breakers for Java backend applications.
This article curates 19 genuinely terrible code fragments collected from various developers, illustrating common pitfalls such as magic numbers, poorly named variables, misuse of booleans, and overly complex switch statements, and encourages readers to reflect on and learn from these mistakes.
The article explains how java.util.UUID.randomUUID relies on OS entropy, can block threads when entropy is low, shows a real‑world thread‑dump example, and provides three remedies: upgrading the JDK, installing haveged, or switching to /dev/urandom.
This article presents a comprehensive design of a distributed reconciliation system that handles tens of millions of daily payment orders by using a six‑module architecture, Kafka for decoupled state transitions, Hive for large‑scale data processing, and Java‑based plug‑in patterns to achieve six‑nine accuracy and significant operational cost savings.
Learn how to implement both simple parameter checks and complex business rule validations in SpringBoot by leveraging Bean Validation, creating custom annotations like @UniqueUser and @NotConflictUser, and integrating them seamlessly into controllers to ensure data integrity and reduce boilerplate logic.
This guide walks through creating custom Spring MVC core components—including DispatcherServlet, HandlerMapping, HandlerAdapter, and ViewResolver—using annotations and Java code to gain full control over request handling, parameter resolution, and response rendering in backend development.
This article provides a comprehensive explanation of the Composite Reuse Principle (CRP), covering its definition, background, advantages over inheritance, UML representation, practical Java code examples, and guidelines for choosing between composition and inheritance in object‑oriented design.
The article explains why forcibly stopping a Java thread is unsafe, outlines common scenarios that require thread exit, compares graceful and forced termination, and presents practical techniques such as flag checks and Thread.interrupt() to achieve safe and predictable thread shutdown.
This guide walks through adding Camunda 7 to a Spring Boot project, covering Maven dependencies, configuration files, database schema, BPMN modeling, task types, gateways, API usage, variable handling, listeners, and deployment, providing a complete end‑to‑end workflow solution.
This article introduces Java’s bytecode fundamentals, explaining how the JVM translates compiled class files into platform‑independent instructions, the role of dynamic linking, stack frames, operand stacks, and common bytecode mnemonics, while providing code examples and visual diagrams to deepen understanding.
This article explains how to reduce repetitive Java backend code by extracting common logic into abstract classes, applying the Template Method and Factory patterns, using custom annotations with reflection for API serialization, and leveraging bean‑mapping utilities to copy properties between DTOs and DOs.
This guide presents a curated list of essential Java libraries—including testing, JSON, logging, utility, XML, Excel, bytecode, collections, HTML parsing, encryption, embedded databases, serialization, networking, Lombok, and Testcontainers—that can dramatically improve productivity and code quality for backend development.
This article explains how to use a bitmap to store 6 billion URLs within 1 GB of memory and introduces Bloom filters as a space‑efficient probabilistic structure for deduplication, providing memory calculations, usage scenarios, and Java code examples.
The 2023 State of Java report, based on a survey of over 2,000 Java professionals, reveals that Java adoption stays strong with most companies using LTS versions, migrating to the cloud, confronting rising costs and security challenges, while Oracle's market share declines in favor of OpenJDK alternatives.
This article introduces Java virtual threads, compares them with traditional platform threads, demonstrates multiple creation and execution patterns, showcases performance benefits through code examples, and explains structured concurrency as a preview feature for building high‑throughput, scalable backend applications.
This article explains why hard‑coded if‑else logic hinders extensibility, introduces the Strategy pattern, shows its structure and Java implementation for data synchronization, then enhances the design with a Factory to decouple object creation, concluding with best‑practice recommendations.
A Java ToB system struggled to meet a 500 requests‑per‑second target, revealing hidden bottlenecks such as slow SQL, excessive logging, thread‑pool misconfiguration, high CPU usage from Spring bean creation, and improper Redis usage, which were systematically identified and mitigated.
This article experimentally compares three Java‑based insertion strategies—MyBatis without transaction, plain JDBC with and without transaction, and JDBC batch processing—with and without transactions, measuring how they affect the time required to insert tens of millions of rows into MySQL.
After migrating a project to the MDP framework based on Spring Boot, the author observed swap overuse and physical memory far exceeding the 4 GB heap; using JVM native memory tracking, gperftools, strace, pmap, and a custom allocator, they traced a native‑memory leak to Spring Boot’s ZipInflaterInputStream during JAR scanning and resolved it by limiting scan paths.
This article explains when adding consumers to a RocketMQ topic improves message consumption, the reasons for consumer pull delays, and details six MessageQueue allocation strategies—including average, round‑robin, custom, machine‑room, nearby, and consistent‑hash—accompanied by code examples.
This article introduces the fundamentals of distributed systems, provides an overview of Apache Kafka’s architecture and core components, explains how Kafka ensures message ordering within partitions, and outlines Java‑based strategies to guarantee ordered consumption, including single‑partition consumption, partition assignment, and key‑based partitioning.
This article analyzes the constraints of loading one billion 1 KB log records from distributed storage into MySQL, evaluates single‑table limits, proposes batch‑insert, sharding, storage‑engine, file‑reading, and distributed‑task coordination techniques to achieve high‑speed, ordered, and reliable data ingestion.
A scheduled task system that frequently accesses MySQL and cache crashes at night due to a SIGSEGV in the HotSpot JVM caused by JIT compilation of hotspot code, and the article explains the JVM internals, JIT behavior, and provides configuration and driver downgrade solutions to prevent the failure.
