This article investigates the mysterious "prevent gc" comment in RocketMQ source code, explains how Thread.sleep(0) interacts with JVM safepoints and counted loops, and demonstrates practical fixes by changing loop indices or inserting explicit safepoint calls.
This article explains how the JVM creates and manages FinalReference objects, how they interact with the finalize() method, and how the ZGC and other GC phases discover, revive, and eventually reclaim objects, detailing the roles of ReferenceHandler, FinalizerThread, and related internal data structures.
This article explains the concept of dynamic proxies, compares Spring's JDK‑based and CGLIB‑based proxy implementations with code examples, and shows how they power Spring AOP for cross‑cutting concerns such as transactions and logging.
This article presents a comprehensive collection of Spring Boot best practices—including package structuring, design patterns, starter usage, dependency management, constructor injection, SLF4J logging, pagination, caching, exception handling, naming conventions, and code quality tools—to help developers build more efficient, maintainable, and robust Java backend applications.
This article explains how Java's Thread.sleep(0) works, its native implementation, why it is used in RocketMQ source code, and how the call influences JVM garbage‑collection, safe‑point insertion, and CPU scheduling to improve multithreaded performance.
This article explains RabbitMQ’s architecture, details its core components, walks through the five main messaging patterns with visual diagrams, provides complete Java code examples for each pattern, and discusses reliability mechanisms such as acknowledgments, persistence, and practical use‑case scenarios.
This article explains how Java's CompletableFuture extends traditional concurrency tools with rich APIs for parallel execution, chaining, error handling, and timeout management, providing clear code examples that demonstrate building maintainable asynchronous applications.
This article introduces the URule rule engine, explains its background, installation steps, core concepts such as variable, constant, parameter, and action libraries, demonstrates both wizard‑style and script‑style rule sets, and provides complete Spring Boot integration code with real‑world usage scenarios.
This article presents a comprehensive guide to designing and implementing a Java‑based MySQL large‑table migration tool using microservice architecture, multiple design patterns, multithreading, custom logging, and flexible migration modes, complete with code snippets, repository links, and deployment considerations.
This article explains how HTTP's stateless nature requires session or token mechanisms for preserving user state, compares session‑based and JWT‑based authentication, details JWT structure, and provides a complete Java implementation with code examples.
This article introduces PowerJob, a young yet mature distributed task scheduling framework, explains why it was chosen, details its architecture, high‑availability design, deployment steps, and demonstrates various job types—including standalone, broadcast, map, and MapReduce—along with CRON, fixed‑rate, and fixed‑delay scheduling configurations.
This article explains the concept of remote calls, compares Feign and OpenFeign, walks through the step‑by‑step setup in a Spring Cloud project, and deeply analyzes the scanning, registration, dynamic proxy creation, MVC annotation parsing, request dispatch, Ribbon load‑balancing, and response handling mechanisms of OpenFeign.
This article explains common scenarios that cause MySQL or Java processes to consume 900% CPU, walks through step‑by‑step diagnosis using Linux tools, and provides concrete optimization techniques such as indexing, caching, thread analysis, and code adjustments to bring CPU usage back to normal levels.
This article examines the performance differences between using the '+' operator and StringBuilder for string concatenation in Java, presenting JUnit benchmark tests for simple concatenations and looped concatenations, analyzing compiled bytecode, and concluding that '+' is suitable for simple cases while StringBuilder excels in loops.
This article explains the Chain of Responsibility pattern, compares self‑driven and handler‑driven implementations with Java code, and demonstrates how major frameworks such as Spring Interceptor, Servlet Filter, Dubbo, and Sentinel realize the pattern, followed by practical usage scenarios.
This tutorial walks through designing a button‑level user permission system—including a five‑table database schema, Spring Boot + MyBatisPlus project setup, code generation, menu CRUD operations, recursive menu tree construction, role‑based permission queries, and annotation‑driven request authorization—complete with runnable code snippets and sample data.
This article explains Java generics, covering their syntax, type parameters, benefits such as compile‑time type safety and code reuse, demonstrates bounded and unbounded type erasure, and illustrates the need for bridge methods with detailed code examples.
This article provides an in‑depth explanation of the Spring Boot startup process, enumerates the key extension points, demonstrates their execution order with sample code and logs, and offers practical recommendations for correctly initializing RPC, MQ, and HTTP traffic.
The article explains why comparing floating‑point numbers with == in Java often yields unexpected results, describes the IEEE‑754 representation of float and double, demonstrates common pitfalls through code examples, and provides step‑by‑step methods for converting decimal fractions to binary.
This article provides a detailed overview of Spring MVC request‑mapping annotations, Spring Bean stereotypes, dependency‑injection and scope annotations, as well as Spring Boot conditional and lifecycle annotations, complete with code examples and usage tips for Java backend development.
Java's BigDecimal class offers arbitrary‑precision decimal arithmetic, requiring method calls like add, subtract, multiply, and divide instead of operators, and should be instantiated via String or valueOf to avoid double‑precision errors, with careful handling of scaling, rounding, formatting, and comparison for exact financial calculations.
This guide explains how to customize the Spring Boot startup banner by creating a banner.txt file, using ANSI color codes, retrieving various Spring Boot properties, and optionally disabling the banner altogether through code changes.
This article thoroughly explains the Spring Boot startup sequence, detailing each lifecycle extension point, common pitfalls with early RPC, HTTP, and MQ traffic, and provides code examples and answers to eleven critical questions to help developers master Spring initialization and avoid runtime failures.
This article explains why the Spring MVC @RequestBody annotation cannot be applied to multiple parameters in a single handler method, detailing the internal request‑body reading process, the resulting HttpMessageNotReadableException, and how to correctly handle multiple data parts using a single DTO.
This article provides a comprehensive guide to Java thread pools, covering common interview questions, core parameters, execution flow, lock mechanisms, custom queue implementations, rejection policies, best practices, monitoring strategies, and dynamic tuning with DynamicTp, all illustrated with code examples and diagrams.
This article analyzes the memory increase observed after enabling Log4j2 asynchronous logging in Java services, examines root causes such as thread‑local reuse and large char[] allocations, and presents configuration and code changes—including disabling thread‑locals and limiting message size—to prevent heap growth and improve performance.
This article explains why parameter validation is essential in Java web development, compares traditional manual checks with validator libraries, demonstrates practical usage of Bean Validation, Hibernate‑Validator, and Spring Boot starter‑validation, and covers advanced topics such as nested validation, group validation, custom constraints, and the underlying validation mechanism.
This article explains how to flexibly switch between Spring's built‑in @Scheduled tasks and XXL‑JOB implementations without changing existing code, by using conditional auto‑configuration, annotation scanning, task registration, log redirection, and a ready‑to‑use starter, complete with configuration examples and runtime verification.
This tutorial demonstrates nine practical ways to handle SpringBoot 3.2.5 request data, including Optional‑wrapped parameters, direct Servlet API access, retrieving the authenticated Principal, extracting method and locale, reading InputStream, using HttpEntity for headers and body, building request URIs, handling multipart parts, and passing flash attributes on redirects.
This article explains the fundamentals of Role‑Based Access Control (RBAC), its model classifications, permission concepts, and user‑group usage, then demonstrates how to implement RBAC in a Spring Security application, including in‑memory authentication, JWT integration, JSON login, and password encryption techniques.
This article explains how to use MyBatis dynamic SQL tags—including foreach, concat, choose, selectKey, if, where, set, trim, and sql fragments—providing clear examples and tips to write concise, error‑free XML mappings for Java backend applications.
This article demonstrates how a custom event published from a constructor in Spring Boot 3.2.5 can cause a deadlock, explains the underlying lock contention, and provides two solutions: using SmartInitializingSingleton to defer publishing and upgrading to Spring 6.2's multithreaded bean initialization.
The article explains common pitfalls in Java API design—such as inconsistent return formats, missing error handling, irrelevant parameters, and improper use of maps or JSON strings—and demonstrates how adopting a unified ResultBean structure together with AOP can improve readability, error management, and testability of backend services.
This article provides a deep technical analysis of Spring Boot's startup process, explains every relevant extension point, demonstrates how to log and verify execution order with sample code, answers eleven common questions about bean initialization, and offers practical guidance on when to safely open RPC, MQ, and HTTP traffic.
This article explains how to design a plug‑in architecture for a data‑governance service by using a custom URLClassLoader, Spring bean registration, and XXL‑Job integration to dynamically load, start, stop, upgrade, and unload individual governance tasks without restarting the whole service, and also shows how to persist the configuration in local YAML or Nacos.
The article shows how to implement a hot‑plug AOP system in Spring that lets users enable or disable logging at runtime by scanning, registering, and deregistering Advice/Advisor/Pointcut beans through the bean factory, demonstrated with a REST endpoint that adds or removes a logging interceptor.
This article explains how to build a clean, maintainable Controller layer in Java Spring by separating responsibilities, using unified response structures, applying ResponseBodyAdvice for automatic wrapping, implementing parameter validation with JSR‑303, and handling custom exceptions through centralized advice, illustrated with comprehensive code examples.
This article walks through Nacos's LongPollingService source code, showing how it extracts headers, calculates timeouts, detects configuration changes, enforces connection limits, and uses Servlet 3.0 AsyncContext to handle long‑polling without blocking threads.
This article walks through the problem of traditional session‑based captcha login, compares it with a modern front‑back‑separated architecture, and provides a step‑by‑step implementation using Spring Boot, Kaptcha, and Redis, including full code snippets, configuration classes, and flow diagrams.
To gracefully shut down a Java thread pool, use ExecutorService's shutdown() to reject new tasks, awaitTermination() to wait for running tasks with optional timeout, handle exceptions, and optionally invoke shutdownNow() for forced termination, as illustrated by code examples from Dubbo3 and RocketMQ.
The article explains a bug in Java's ConcurrentHashMap.computeIfAbsent that can cause recursive updates and infinite loops, leading to CPU spikes, and shows that newer Java versions throw an IllegalStateException while recommending avoiding nested computeIfAbsent/putIfAbsent calls, with a code example.
This article explains how to use SLF4J MDC together with a TraceId header to correlate logs across threads, services, and distributed tracing tools like SkyWalking, providing code examples for filters, Feign interceptors, thread‑pool adapters, and Logback configuration.
This article explains why RequestContextHolder fails to retrieve the HttpServletRequest in a multithreaded Spring MVC environment, demonstrates the problem with a concrete example, analyzes the underlying thread‑local handling of request attributes, and clarifies the default non‑inheritable behavior that leads to null requests.
This article provides an in‑depth tutorial on Java's BigDecimal class, covering its purpose, common constructors, essential arithmetic methods, comparison techniques, formatting with NumberFormat, handling of division exceptions, and a utility class offering precise add, subtract, multiply, divide, rounding, and comparison operations.
The article benchmarks Spring Boot and Quarkus for cloud‑native Java apps, showing Quarkus native images start up twice as fast, use less memory, and produce smaller artifacts than Spring Boot, while Spring Boot JVM offers slightly lower latency, and a migration guide demonstrates API compatibility and code reuse.
ConcurrentHashMap forbids null keys and values because allowing nulls creates ambiguous results in concurrent environments, making it impossible to distinguish between a missing entry and an entry explicitly mapped to null, which could compromise thread safety, as explained by Doug Lea’s design rationale.
This article demonstrates three approaches for invoking external services in Spring Boot applications—using raw HttpClient, the RestTemplate utility, and Feign clients—providing code samples, configuration steps, and tips for handling headers and tokens.
This article explains how Feign uses Ribbon for remote calls, details Ribbon's load‑balancing mechanisms, enumerates built‑in strategies, and demonstrates how to enable eager‑load mode to pre‑warm clients and avoid first‑request latency in Java microservice environments.
This article explains how to secure Spring Boot API responses using RSA asymmetric encryption and digital signatures, covering RSA fundamentals, project setup, Maven configuration, key management, annotation‑driven encryption/decryption, front‑end JavaScript encryption with JSEncrypt, and practical testing steps.
This article explains the principles and implementation of Java's Compare-and-Swap (CAS) and AbstractQueuedSynchronizer (AQS), illustrating how CAS enables lock‑free algorithms and how AQS underpins high‑level synchronization constructs like ReentrantLock and CountDownLatch, while also providing practical step‑by‑step examples.
This article explains what Java Class Data Sharing (CDS) is, walks through training and running a Spring Boot application with CDS, and demonstrates how startup time can be reduced by nearly one second, while comparing CDS with CRaC and GraalVM for Java performance optimization.
Learn how to integrate Apache Tika into a Spring Boot application to parse a wide range of document formats, including the necessary Maven dependencies, XML configuration, custom configuration class, and usage examples, enabling efficient content extraction and processing within your Java backend.
The article explains how Fast‑Retry, an asynchronous multi‑task retry framework, dramatically outperforms synchronous retry libraries like Spring‑Retry and Guava‑Retry when handling massive workloads, and provides step‑by‑step code examples, performance benchmarks, and integration tips for Java developers.
This article presents a comprehensive Spring Boot backend architecture for the XiaoLe project, detailing design principles, a ten‑module Maven structure, key pom configurations, and the rationale for using Maven import to manage dependencies.
This article explains how to track online users by storing their identifiers in a Redis sorted set, using zadd to add entries, zrangeByScore to query active users, and zremrangeByScore and zrem to clean up expired or logged‑out sessions, with code examples in Java and JavaScript.
MyBatis dynamic SQL lets developers construct conditional queries at runtime using tags like if, where, trim, choose, set, foreach, sql, include, and bind, simplifying complex statements, avoiding manual string concatenation, supporting batch operations, reusable fragments, and one‑to‑many mappings while improving flexibility and maintainability.
This guide explains how embedding a large‑language‑model AI into a CI pipeline can automate code reviews, cut review time, improve consistency and accuracy, and ultimately raise development efficiency and code quality while reducing manual effort and communication overhead.
The Chinese Patent CN112905176B granted to Industrial and Commercial Bank of China describes a SpringBoot‑based backend implementation method that extracts operation data, maps business IDs to configuration, builds conditional expressions, and processes data, aiming to reduce development changes, lower costs, and improve system stability.
This article presents a configurable OLAP framework that streamlines multi‑dimensional, multi‑metric analysis by separating core and interaction domains, using metadata‑driven modeling, runtime request handling, and Maven‑based integration to accelerate development and improve query performance.
This article explains the drawbacks of manual code review, demonstrates how AI large‑model services can automate and improve review quality, and provides a step‑by‑step guide—including a Java script and CI pipeline configuration—to embed JD's Chatrhino model into a continuous integration workflow, resulting in higher efficiency, accuracy, and reduced development cycle time.
This article provides a comprehensive guide to MyBatis dynamic SQL, covering foreach loops, conditional if, choose, selectKey, trim, and sql fragments, with detailed explanations and full XML and Java code examples to help developers write efficient, error‑free mappings.
This article explains how to prevent duplicate API calls in Java backend systems by using debounce techniques, shared Redis caches or Redisson distributed locks, and provides complete annotation‑based implementations with code examples, key generation strategies, and testing results to achieve idempotent interfaces.
This article investigates a concurrency bug in MyBatis caused by OGNL expression evaluation using reflection, explains the root cause through stack trace and source code analysis, and proposes solutions such as upgrading MyBatis or avoiding private inner‑class methods like Arrays.asList.
This article explains Java virtual threads, compares them with traditional OS threads, shows how to enable them in SpringBoot 3, and presents performance benchmarks demonstrating up to 200‑fold speed improvements for I/O‑bound workloads.
This article details how to switch a SpringBoot‑MyBatisPlus‑MySQL application to PostgreSQL, covering driver addition, JDBC configuration changes, numerous SQL and type‑conversion pitfalls, helper scripts for bulk column updates, and essential migration notes.
This article explores why using an Integer as a lock can cause synchronized to malfunction, demonstrates the issue with a ticket‑selling example, analyzes thread dumps and JVM bytecode, and presents reliable alternatives such as class‑level locks or map‑based lock objects.
This article compares Java's standard ThreadLocal with Netty's FastThreadLocal, explains their internal mechanisms, shows practical code examples, runs a JMH microbenchmark, and discusses performance, memory management, and usage scenarios to help developers choose the right thread‑local storage solution.
This article explains how to let users dynamically enable or disable logging by managing Spring AOP advice at runtime, covering prerequisite concepts, core hot‑plug logic, detailed Java code for installing and removing plugins, a step‑by‑step demo, and a concise summary of the approach.
This article explains how to use Log4j's Mapped Diagnostic Context (MDC) to generate, propagate, and record a traceId across micro‑service calls, providing a low‑cost, non‑intrusive solution for full‑stack log tracing and debugging.
This article introduces eight ready‑to‑use Java Stream APIs—including Stream.ofNullable, Stream.iterate, collectingAndThen, dropWhile/takeWhile, IntStream, teeing, concat, and partitioningBy—showing how each can cleanly handle nulls, generate sequences, transform collections, and combine streams with concise code examples.
This article provides a comprehensive overview of Hystrix, covering its core functions such as fault isolation, service fallback, timeout control, and circuit breaking, and walks through adding Maven dependencies, annotating methods with @HystrixCommand, configuring properties, and explaining the underlying circuit‑breaker and thread‑pool isolation principles.
This comprehensive guide walks you through the concepts of Single Sign-On, the mechanics of JWT, RSA asymmetric encryption, and step‑by‑step integration of Spring Security with JWT, providing full Maven project setup, configuration files, utility classes, custom filters, and testing instructions for a robust distributed authentication system.
JetBrains' 2024.1 update for IntelliJ IDEA introduces full‑line code completion, Java 22 support, a revamped terminal, AI Assistant enhancements, improved version‑control integration, faster Maven project loading, advanced debugging, Spring framework upgrades, and numerous UI and refactoring refinements, all aimed at boosting developer productivity.
A mis‑handled exception in a ScheduledExecutorService can silently halt the entire scheduled thread pool, causing critical periodic jobs to stop; this article explains the underlying delay‑queue and thread‑pool mechanics, shows reproducible code, and provides practical safeguards to keep scheduled tasks alive.
This article explains what Java virtual threads are, how they differ from regular threads, shows how to enable them in SpringBoot 3.1.2 with Java 20, and presents performance benchmarks that demonstrate up to 200‑fold speed improvements for IO‑bound workloads.
The article explains how to embed the open‑source URule rule engine into a Spring Boot application, covering installation, datasource configuration, library definitions for variables, constants, parameters and actions, creating visual or script rule sets and decision tables, and demonstrates a membership‑upgrade use case.
This article explains the fundamentals of finite state machines, introduces Spring Statemachine, demonstrates how to model order lifecycle states, configure persistence with memory and Redis, handle exceptions during state transitions, and use AOP to log transition results, providing complete Java code examples.
This tutorial explains how to set up a simple yet powerful Java logging solution by installing Loki and Grafana via Docker, configuring Loki4j in a Spring Boot project, and visualizing logs in Grafana, providing step‑by‑step instructions and sample code.
This article explains how to create a custom insertable annotation processor in Java that automatically injects the jar version into component constants during the Gradle build, eliminating manual updates and enabling version monitoring via Prometheus.
This article demonstrates how to use the junixsocket library to add Unix domain socket support to Java applications, providing Maven dependency details, full server and client code examples, and cross‑language testing with a Go server implementation.
This article explains how to create a custom annotation and MyBatis‑Plus interceptor that automatically injects data‑permission WHERE clauses based on the current user's role, covering both a basic implementation and an advanced version with role‑based scope handling, complete with configuration and usage examples.
This article explains how Java's Arrays.asList creates a fixed‑size list that throws UnsupportedOperationException on add/remove, and how ArrayList.subList returns a mutable view whose non‑structural changes affect both the original list and the sublist while structural changes can trigger ConcurrentModificationException, providing code examples and practical guidelines.
This article explains the Java BigDecimal class, detailing its internal storage mechanisms, precision handling, immutable design, and common pitfalls, and provides best‑practice guidelines for constructing, comparing, dividing, and converting BigDecimal values to ensure accurate numerical computations.
This article explains why iterating a Java HashMap with keySet() involves two passes, examines the underlying iterator implementation, and walks through the relevant source code of HashMap’s KeySet, KeyIterator, and HashIterator classes to clarify the internal traversal mechanism.
This tutorial introduces Spring AI and Spring Cloud Alibaba AI, explains their core features, shows how to set up a Maven project with the required dependencies, and provides step‑by‑step code examples for invoking text, image, and audio generation models using Spring Boot.
This article explains the concepts of concurrency, parallelism, and serial execution, describes common multi‑core scheduling algorithms, and demonstrates Java's concurrent programming tools—including Future, Fork/Join, Stream API, and CompletableFuture—through clear code examples and practical guidelines.
This article explains how to achieve reliable API idempotency in Spring Boot applications by using Redis for token storage, defining a custom @AutoIdempotent annotation, implementing token generation and validation services, configuring an interceptor, and providing test cases to demonstrate the workflow.
This article explains how to implement a configuration‑driven mechanism that dynamically switches between Spring's native @Scheduled tasks and XXL‑JOB execution, automatically registers jobs, disables Spring's scheduler when needed, and forwards logs to the XXL‑JOB console, providing a complete starter solution for backend developers.
This article explains why Maven runs unit tests during the package phase, describes the Maven lifecycle, and provides several practical methods—including command‑line flags, pom.xml configuration, and IDE settings—to skip tests when building a Java project.
This guide walks you through creating a dynamic, real‑time data visualization dashboard—covering design mockups, requirement planning, architecture using Echarts for the front‑end and Java for the back‑end, JSON data handling, deployment without installation, configuration steps, code structure, and source acquisition.
This article explains what Java Class Data Sharing (CDS) is, provides detailed commands for training and using a CDS archive with a Spring Boot demo, and shows how startup time can be cut by nearly one second, helping developers choose the right Java startup optimization technique.
This article dissects Pulsar’s storage layer by examining the Bookie component, detailing its architecture, the sequential write‑ahead log, ledger management, journal handling, caching mechanisms, and the complete read/write call chains with concrete code examples and performance considerations.
This article explains the roles of DTO, VO, and PO in Java applications, compares manual property copying with BeanUtils and MapStruct, provides complete code examples for both approaches, and offers guidance on choosing the appropriate method based on performance and project needs.
This article explains how to design an effective Java controller layer by separating concerns, introducing a unified response structure, applying global response wrapping, leveraging Spring's validation mechanisms, and handling custom exceptions to produce concise, maintainable backend code.
This article explains the concepts and step-by-step implementation of dynamically loading JAR packages in Spring Boot applications, covering built‑in classloader usage, creating JARs, and leveraging third‑party libraries to enhance flexibility and extensibility.
This article explains how to use Spring WebFlux's reactive, non‑blocking model to create a server‑sent events (SSE) endpoint that streams text data, and demonstrates a front‑end Vue implementation that splits the stream into characters to produce a realistic typing animation.
Java developers constantly battle NullPointerExceptions, a historic flaw introduced by Tony Hoare, but modern JDKs provide clearer messages and defensive techniques—such as explicit null checks, utility methods, avoiding null returns, and using Optional—can dramatically reduce these runtime errors.
This article provides a step‑by‑step tutorial on Apollo's configuration center, covering its core concepts, four‑dimensional model, client design, Spring Boot integration, testing of dynamic updates, and deployment via Docker and Kubernetes for cloud‑native applications.
This article explains how to use a custom CommonContext with conditional logging and lambda‑based delayed evaluation to quickly trace issues in high‑concurrency Java back‑end systems without degrading performance, and demonstrates the performance improvements through before‑and‑after measurements.
This article explains how Java developers can use thread pools and Apache Commons Pool2's GenericObjectPool to create a reusable process pool, covering the underlying concepts, required interfaces, Maven dependencies, configuration options, and practical code examples to improve performance.
