This article explains how to use the MyBatis @MapKey annotation to map query results into a Java Map, provides a concrete code example, and delves into the internal processing steps—including MapperProxy, MapperMethod, MethodSignature, and DefaultMapResultHandler—that enable this functionality.
This article explains why a Java method that returns a value inside a try block still yields the original value when a finally block modifies the variable, using bytecode inspection, protection mechanisms, and JVM exception‑table behavior to reveal the underlying execution order and performance implications.
A Java rule‑engine experiences occasional 1‑2 second Young GC pauses after warm‑up, caused by dynamic promotion thresholds that trigger massive object promotion, and the article explains the root cause, demonstrates log analysis, and provides JVM tuning steps to eliminate the long pauses.
This article explains how to redesign a Java data model so that a single sessionId is stored at the outer level while multiple sceneId/sceneName pairs are nested inside a sceneList, and shows the required MyBatis mapper, XML mapping, service, and controller implementations.
This article introduces MyBatis‑Flex, a lightweight and high‑performance MyBatis enhancement framework, outlines its key features, compares it with similar tools, presents benchmark results, lists supported databases, and provides a step‑by‑step quick‑start tutorial with complete code examples for Spring Boot integration.
This guide explains how Spring Boot 3.2 leverages the OpenJDK CRaC project to create and restore JVM checkpoints, dramatically reducing application startup time through automatic and manual checkpoint techniques, complete with required dependencies, installation steps, and performance results.
This article explains how to mask sensitive fields in Java logs, demonstrates the pitfalls of shallow‑copying nested Maps during masking, and shows a robust solution using Guava's Maps.transformEntries to perform lazy, view‑based deep transformation without mutating the original data structures.
This article walks through a Java junior's code review, showing step‑by‑step how simple null‑checks evolve into constant definitions, static methods, enums, Optional usage, and finally strategy‑pattern implementations, illustrating both useful refactoring and the risk of over‑design.
This article explains how to deploy and use Alibaba Canal to capture MySQL binlog changes, configure MySQL and Canal, and write Java code that listens to row‑level events for synchronizing data to other systems such as Redis or Elasticsearch.
This article examines how MySQL's JDBC driver manages ResultSet resource release, the internal close mechanisms, and the concurrency limitations of Statement objects, illustrated with code excerpts and a Groovy virtual‑thread demo that reveals runtime exceptions when ResultSets are accessed after implicit closure.
This article analyzes a Spring MVC issue where a batch template download failed due to missing configuration, explores how @ResponseBody interacts with manual stream writes, presents code examples, debugging insights, and offers best‑practice recommendations for reliable file‑download endpoints.
This article provides a step‑by‑step guide on integrating Spring Batch with Spring Boot, covering business scenarios, database setup, Maven dependencies, configuration of JobRepository, JobLauncher, Job, Step, ItemReader, ItemProcessor, ItemWriter, listeners, validators, execution via REST endpoints, troubleshooting with Druid and switching to HikariCP, and demonstrates processing CSV and database data in large batches.
This article explains why retry mechanisms are essential for distributed Java applications and walks through eight practical implementations—including loop, recursion, Apache HttpClient, Spring Retry, Resilience4j, custom utilities, asynchronous thread‑pool retries, and message‑queue based retries—plus best‑practice guidelines to avoid common pitfalls.
RediSearch, a low‑memory Redis module, offers comparable full‑text search capabilities to Elasticsearch, with faster indexing and query performance on modest hardware; this article explains its features, compares benchmarks, shows Docker installation, and provides Java/Jedis code examples for creating, querying, and managing indexes.
This article presents Qunar Travel's "system slimming" project, describing how observability techniques, a two‑stage strategy, and automated tooling were used to identify and remove unused services and code, achieving a 50% reduction in code size, a 26% cut in services, and measurable improvements in reliability and release efficiency.
This article explains the concept of idempotency, outlines common strategies, and provides a complete Spring Boot implementation that uses Redis, a custom @AutoIdempotent annotation, token generation, and a web interceptor to ensure each API request affects the database only once.
This article provides a comprehensive guide to KafkaConsumer, covering message delivery semantics (at‑most‑once, at‑least‑once, exactly‑once), practical exactly‑once implementations, consumer rebalance triggers and strategies, partition assignment algorithms, thread‑safety considerations, and detailed Java code examples of the consumer workflow.
This tutorial walks through advanced Spring Cloud Function features—including handling HTTP request parameters, function mapping and filtering rules, functional bean definitions, visualization via Actuator, and package scanning—providing code examples and configuration tips for Spring Boot 2.7.15 projects.
This article explains why Java processes in Kubernetes pods often encounter OOMKilled despite correct JVM heap settings, analyzes the discrepancy between JVM‑reported memory and container metrics, and provides practical steps such as adjusting MaxRAMPercentage and pod memory limits to stabilize memory usage.
This article walks through the complete process of adding Dataway to a Spring Boot application, covering Maven dependencies, configuration properties, database schema creation, data source setup, Hasor module integration, enabling Hasor in Spring, and finally creating and testing API endpoints using both SQL and DataQL, all illustrated with concrete code snippets and log output.
The paper presents a centralized online batch‑processing framework for large‑scale promotion systems, where applications integrate via an SDK, a task‑center schedules and dispatches sub‑tasks through RocketMQ to Dubbo‑enabled containers, employing MapReduce‑style splitting, Guava rate‑limiting, heartbeat health checks, and has successfully handled over 1.3 million tasks during Double‑11.
This article examines common Java jar obfuscation tools, identifies their limitations for protecting both proprietary code and third‑party dependencies, and proposes a lightweight Maven‑based encryption combined with a runtime agent that decrypts classes on demand while keeping performance impact under five percent.
This article explains the underlying principles and step‑by‑step configuration for integrating Spring Boot with MyBatis to manage multiple data sources, covering BeanFactory, FactoryBean, SqlSessionFactoryBean setup, datasource properties, mapper scanning, and sample controller code for accessing distinct databases.
An in‑depth analysis reveals how the JDK’s DiscardPolicy rejection strategy can cause invokeAll to block indefinitely, exposing a subtle thread‑pool bug, the official response, and practical code examples demonstrating the issue and ways to avoid it.
Spring 6 offers four powerful ways to perform remote HTTP calls—WebClient, RestTemplate, HTTP Interface, and RestClient—each with distinct APIs, configuration options, and usage patterns, and this guide walks through their setup, method signatures, request handling, and error management for Java developers.
This article provides a comprehensive overview of the Caffeine local cache library, covering its fundamentals, configuration options, loading strategies, eviction policies, statistics, and detailed steps for integrating Caffeine with Spring Boot using annotations and custom cache managers.
This guide explains why thread pools are essential in Java, walks through factors such as CPU cores, I/O latency, and workload characteristics, and provides formulas and concrete code examples for calculating the ideal pool size for both CPU‑bound and I/O‑bound tasks.
A seasoned Java engineer shares his journey transitioning to Rust, highlighting Rust’s advantages for CLI tools, superior resource utilization, easier concurrency and async programming, while also acknowledging Java’s strengths in rapid feature delivery, mature ecosystem, and ease of learning, and discussing practical migration considerations.
This article presents more than ten practical techniques for writing faster, cleaner Java for‑loops, covering basic size caching, reverse iteration, iterator usage, enhanced for‑loops, nested loop reduction, exception handling placement, and method‑call minimization to improve overall program performance.
This article explains various web message‑push techniques—including short and long polling, iframe streaming, Server‑Sent Events, MQTT, and WebSocket—provides detailed Java and JavaScript code samples, compares their trade‑offs, and shows how to integrate them in a Spring Boot application.
This article introduces the PowerJob distributed task framework, explains why it was chosen, details its architecture and high‑availability design, demonstrates various job types—including standalone, broadcast, map, and map‑reduce—with Java code examples, and covers scheduling options such as CRON, fixed‑rate, and fixed‑delay execution.
This article explains the Spring MVC return‑value handling mechanism, demonstrates how to implement a custom HandlerMethodReturnValueHandler, register it correctly in a WebMvcConfigurer, and troubleshoot why the default processor may override custom handlers.
Graceful Response is a Spring Boot component that unifies response wrapping, global exception handling, and custom error codes, helping developers reduce boilerplate, improve readability, and accelerate API development while supporting validation and customizable response styles.
The article reviews a Scala meetup where experts compare Java and Scala, highlighting Scala's stronger expressiveness, type inference, pattern matching, safety, and concurrency features, and discusses real‑world adoption, developer experiences, and a recruitment opportunity for a Scala‑focused big‑data team.
This article walks developers through Sermant’s architecture, explaining its plugin mechanism, class isolation, and how to build practical plugins with basic capabilities, unified dynamic configuration, and unified logging, while showcasing real‑world examples and tips for efficient development.
This article explains how positioning a try‑catch block either inside or outside a Java for loop changes exception handling behavior, performance impact, and when to choose each approach based on business requirements.
This article demonstrates how to enable and use Coordinated Restore at Checkpoint (CRaC) in Spring Boot 3.2 with the Spring Petclinic example, covering required dependencies, JVM setup, automatic and manual checkpoint creation, performance measurements, and best‑practice considerations for backend developers.
Switching a Java Netty gateway from GZIP to ZSTD compression using zstd‑jni doubled GC time and introduced heap and Netty off‑heap memory leaks, which were resolved by employing the library’s direct off‑heap API with a NoFinalizer compressor, promptly releasing ByteBufs, avoiding finalize(), and adopting jemalloc to reduce fragmentation.
Using Jackson's ObjectMapper for JSON parsing, this article benchmarks three approaches—creating a new mapper per call, sharing a global singleton, and using ThreadLocal—revealing that a single shared ObjectMapper can achieve up to ten times higher throughput, while ThreadLocal offers only modest gains.
A Java backend developer investigates why an enum‑based status field becomes an empty string during database insertion, tracing the issue through code inspection, Arthas watches, and ultimately discovering a mis‑implemented enum setter caused by a third‑party library.
This article explains Spring's control flow pointcuts, compares them with AspectJ cflow pointcuts, walks through a complete Java example with nested service classes, shows how to configure a ControlFlowPointcut and proxy, and discusses performance implications and usage scenarios.
This article compiles a comprehensive list of IntelliJ IDEA shortcuts, configuration tweaks, and useful plugins—including history navigation, memory settings, Eclipse keymap, code inspection, bookmark management, Maven helpers, and multi‑port debugging—to boost Java developers' productivity and streamline their workflow.
This article reviews Oracle's Java 21 LTS release, outlines its new JEP features, compares it with Java 17, shares upgrade experiences including pom updates and runtime fixes, and evaluates generational ZGC and virtual threads with performance tests and code examples.
Java’s traditional synchronous blocking model wastes thread resources during I/O, leading to scalability limits, while asynchronous, reactive, and especially Java 21’s virtual threads offer non‑blocking execution paths that improve performance and simplify development without complex reactive pipelines.
This tutorial demonstrates how to create a universal CSV/Excel export utility in Java that can handle objects of any class by using reflection to generate headers and rows, leveraging Apache POI and Spring Boot for seamless file generation.
This article provides a comprehensive overview of the lightweight XXL‑RPC framework, covering fundamental RPC concepts, the framework's architecture built on Spring and Netty, detailed provider and consumer implementations, various call types, and the service registry‑discovery mechanism, concluding with practical insights for developers.
This article introduces the Lock4j distributed lock library for Java, outlines its key features and supported backends, provides step‑by‑step Maven dependency setup, Redis configuration, annotation details, and demonstrates both basic and advanced usage patterns including custom executors and lock‑failure strategies.
This tutorial shows how to build a lightweight request‑tracing solution in SpringBoot 3.2 using SLF4J, MDC, custom filters, logback configuration, and a global ResponseBodyAdvice to log and return trace IDs for improved debugging and observability.
Microsoft reports over 2.5 million Java developers using VS Code and outlines a new roadmap, while this guide walks you through installing the JDK, adding the Java extension pack, and creating Java projects in VS Code with troubleshooting tips.
This article provides a comprehensive guide to MyBatis dynamic SQL tags—including foreach, if, where, choose, trim, set, and selectKey—showing how to build flexible queries, handle collections, and avoid common pitfalls with clear code examples and best‑practice explanations.
The article describes a Groovy scripting issue where calling StringBuilder.setLength(0) triggers a NoSuchMethodError, explains Groovy's automatic property generation, demonstrates debugging steps, metaprogramming attempts, and the final workaround that resolves the error.
Learn how to dramatically reduce startup time in large Spring applications by using spring-context-indexer to generate component indexes at compile time, configure Maven or Gradle dependencies, create manual or IDE‑generated index files, support custom annotations, and disable indexing when needed.
Facing uncontrolled log proliferation, the author shares a real-world case of log governance that reduces costs and boosts efficiency by categorizing logs, simplifying formats, consolidating tools, introducing a three‑layer log architecture, and applying stack‑trace reversal techniques with concrete code examples.
This article explains how to implement unified exception handling in Spring Boot applications using @ControllerAdvice, custom Assert utilities, and enum-based error codes, demonstrating code examples, response structures, and best practices for reducing try-catch clutter, improving readability, and handling various HTTP and business exceptions consistently.
This article describes a practical approach to achieve environment‑based data isolation in Java services by adding an env field to tables, using a MyBatis interceptor to rewrite SQL, and defining custom annotations with AOP to control the isolation logic, while sharing code snippets and lessons learned.
The article presents a collection of typical Java backend coding mistakes—ranging from misused ternary operators and poor parameter validation to logging pitfalls, dead code, improper exception handling, AOP self‑invocation issues, Redis resilience problems, and Excel file upload bugs—along with concrete examples, images, and corrected code snippets to help developers avoid and fix them.
This article explains how Spring Boot packages applications as executable Fat JARs, embeds a web server, uses a special launcher, and defines a main class so the JAR can be run with a simple java -jar command, eliminating the need for separate deployment servers.
This article explains how to design and refactor a Java rule engine that supports short‑circuit AND/OR logic, demonstrates the abstraction of rules, shows concrete implementations, and provides a chainable service for executing combined rule sets with example code.
Java 21 introduces critical bug fixes, correcting the precision of Double.toString() and Float.toString() outputs and fixing the erroneous value comparison in IdentityHashMap’s remove(key, value) and replace(key, value, newValue) methods, ensuring expected behavior across versions.
This guide explains how to use Spring's ResponseBodyAdvice to create a unified response wrapper for RESTful APIs, improving consistency, readability, and extensibility while handling common pitfalls such as String return type errors.
This article surveys the most popular Java language enhancements introduced from Java 8 through Java 20—including var type inference, switch expressions, text blocks, records, pattern‑matching instanceof, sealed classes, and improved NullPointerExceptions—providing concise explanations and visual examples to help developers decide which features to adopt during migration.
This article analyzes the problem of scattered try‑catch blocks in Java services, explains why per‑controller exception methods are cumbersome, and presents a unified exception handling solution using @ControllerAdvice, custom Assert utilities, enum‑based error codes, and environment‑aware response formatting, all illustrated with concrete code examples and test results.
This article presents a Java-based rule engine design that separates rule definitions, data transfer objects, and execution logic, demonstrating AND/OR composition, abstract rule templates, concrete implementations, and a fluent API for building and executing complex rule chains.
This tutorial demonstrates how to employ the open‑source Java diagnostic tool Arthas to quickly locate and analyze a high‑CPU problem in a running JVM by leveraging commands such as dashboard, thread, jad, watch, and ognl, complete with code examples and step‑by‑step instructions.
This tutorial introduces Spring Cloud Function, explains its core concepts and benefits for serverless development, and walks through a complete example—including configuration, code snippets, HTTP endpoints, function composition, custom routing, and deployment—so readers can quickly build and test function‑based applications.
This article walks you through the fundamentals of hash tables, explains bucket arrays and hash functions, discusses collision resolution strategies, and provides a complete Java implementation of a simple HashMap called ThirdHashMap with code, tests, and performance notes.
This article explains how HotSpot's C1 and C2 JIT compiler threads work, why they can consume excessive CPU, and provides practical JVM tuning options—including tiered compilation, code‑cache sizing, and compiler‑thread adjustments—to mitigate performance issues.
This article presents a concise tutorial on building a flash‑sale (Seckill) system with SpringBoot, MySQL, Redis, RabbitMQ and a basic HTML/JQuery front‑end, covering architecture, key features, code snippets, over‑selling prevention, rate limiting, and deployment screenshots.
This article walks through a production incident where a Redis Cluster pipeline caused Dubbo threads to block and eventually deadlock, detailing the root‑cause analysis, code inspection, and verification steps using jstack, jmap, and MAT to confirm the deadlock and propose fixes.
This article explains how to achieve automatic request idempotency in Spring Boot applications by using Redis for token storage, custom @AutoIdempotent annotation, and a web interceptor that validates tokens, providing code examples, configuration steps, and testing procedures.
This guide explains RabbitMQ fundamentals—including brokers, virtual hosts, connections, channels, exchanges, queues, producers, and consumers—covers common messaging patterns, provides step‑by‑step Java code for creating connections, declaring exchanges and queues, publishing and consuming messages, handling acknowledgments and confirmations, and shows how to integrate RabbitMQ with Spring Boot.
This tutorial explains how to extend Spring MVC's HandlerMapping by implementing a custom RequestCondition that matches requests based on an x-token header and a custom @AKF annotation, covering code implementation, configuration, testing, and the underlying request‑matching mechanism.
This article examines several drawbacks of the Spring framework—including performance overhead from reflection and proxies, complex configuration, steep learning curve, over‑reliance on the Spring ecosystem, hidden “magic” features, version compatibility challenges, and misuse of dependency injection—illustrated with Java code examples.
This article explains the recent correction in Alibaba's developer manual that replaces the ambiguous "expansion count" of HashMap with the precise "resize count", details the conditions under which HashMap triggers resize during the first put operation, and shows why storing 1024 elements in JDK 1.8 results in eight resize calls.
This guide explains Spring’s @Import annotation, covering three import strategies—direct class array, ImportSelector, and ImportBeanDefinitionRegistrar—through detailed code examples, usage scenarios, and important version notes, helping developers improve configuration management, code maintainability, and readability in backend Java applications.
This article demonstrates how to build a real‑time equipment monitoring application by using WebSocket for server‑client communication, a Vue.js front‑end to display device status, and a SpringBoot back‑end that broadcasts alerts when abnormal devices are reported.
This article explains how to use Apache Commons GenericObjectPool to implement a reusable process pool in Java, covering the underlying concepts, required dependencies, custom factory implementation, pool configuration, and example code for borrowing and returning pooled objects.
This article introduces the Hutool Java utility library, outlines its extensive modules such as SecureUtil, HtmlUtil, and CronUtil, provides practical code examples, and explains how it can streamline development, improve security, and simplify scheduled tasks for backend projects.
This article introduces Resilience4j, a lightweight fault‑tolerance library for Spring Boot, explaining its core decorators—CircuitBreaker, TimeLimiter, Bulkhead, and RateLimiter—along with configuration examples, annotation usage, fallback handling, and practical test code to improve system stability and resilience.
This article examines Java string concatenation performance, comparing the '+' operator and StringBuilder in both simple and loop scenarios, presenting JUnit benchmark results, bytecode analysis, and concluding that '+' is sufficient for single concatenations while StringBuilder excels in loops.
Learn how to leverage MyBatis-Plus's built-in CRUD capabilities, create custom SQL methods like SelectByErp, integrate them via a custom SqlInjector, and modify existing operations such as AlwaysUpdateSomeColumnById and UpdateById for sharding scenarios, enabling reusable and efficient data access across your backend.
This article presents a comprehensive set of techniques—including lazy initialization, deferred database connections, selective auto‑configuration, logging level tuning, JVM parameter tweaks, dependency pruning, bean optimization, JIT settings, class‑path scanning reduction, and DevTools restart—to significantly shorten Spring Boot application startup time, each illustrated with clear code examples.
This article walks through the step‑by‑step evolution from raw JDBC to the MyBatis framework, explaining why JDBC should be wrapped, how MyBatis improves connection handling, SQL management, dynamic statements, result mapping, caching, and overall architecture with concrete code examples.
This article evaluates the startup speed, memory consumption, and request‑handling performance of a simple Spring Boot "Hello World" service when run on the traditional JVM compared with a GraalVM‑compiled native binary, using a MacBook M1 and Bombardier for load testing.
This tutorial demonstrates how to prompt Tencent Hunyuan’s large‑model API to generate a Spring Boot project configured for MySQL, create a user table, and implement full JPA‑based CRUD layers—including entity, repository, service, and REST controller—while addressing common null‑field errors and testing the endpoints.
This guide walks through Spring Cloud OpenFeign's core concepts, enabling steps, custom configurations, timeout handling, logging, retry mechanisms, interceptors, fallback strategies, caching, inheritance, compression, and reactive alternatives, providing developers with a comprehensive reference for building robust microservice clients.
The article details a step‑by‑step investigation and optimization of a Java backend service that initially delivered only 50 requests per second under load, covering profiling, slow‑SQL fixes, thread‑pool tuning, JVM memory adjustments, and Spring bean creation overhead to approach the target 500 req/s.
This article explains why using Java's BigDecimal for monetary values ensures precise, immutable, and correctly rounded calculations, compares it with float, double, long, and int, and provides best‑practice code examples for constructing, computing, and formatting financial numbers.
This article provides a comprehensive, step‑by‑step overview of MyBatis’s architecture—including its three‑layer design, configuration parsing, proxy generation, and SQL execution process—while highlighting key features such as SQL mapping, dynamic SQL, parameter and result mapping, transaction management, connection‑pool integration, and second‑level caching.
This guide explains how to create a Spring Boot custom HTTP message converter and argument resolver, register them, and use a @Pack annotation to parse a simple 'name:张三,age:20' request body into a Users object, enhancing backend flexibility.
This article explains why the synchronized keyword cannot lock local variables in Java, demonstrates the behavior with multithreaded code examples, and shows that only class member variables can be effectively synchronized to control concurrent access.
This article introduces multiple Java approaches for sending HTTP GET and POST requests, covering the built‑in HttpURLConnection class, Apache HttpClient, Square's OkHttp, and Spring's RestTemplate, with step‑by‑step explanations and complete code examples for each method.
This article provides a comprehensive overview and comparative analysis of popular Java expression engines—including AviatorScript, MVEL, OGNL, SpEL, QLExpress, JEXL, JUEL, and Janino—covering their features, community support, size, performance benchmarks, security settings, usage cases, and syntax differences to guide developers in selecting the most suitable engine for their projects.
This article provides a thorough overview of Java interview topics, covering core language fundamentals, collection frameworks, concurrency mechanisms, Spring Boot transaction handling, database indexing strategies, and network protocol comparisons, all presented in clear English with code examples and diagrams.
This article explains the CQRS architectural pattern, its benefits and challenges, and provides a step‑by‑step guide to implementing CQRS, event sourcing, and asynchronous communication with Spring Boot, Axon, and Apache Kafka in microservice environments.
This article introduces Hutool, a comprehensive Java utility library that consolidates common functions such as file handling, encryption, HTTP, and scheduling into easy-to-use modules, showcases key components like SecureUtil, HtmlUtil, and CronUtil with code examples, and highlights its benefits for reducing development effort.
A ToB system that seemed able to handle 500 requests per second stalled at 50 req/s due to hidden lock contention in prototype‑scoped Spring beans, slow SQL updates, excessive logging, and thread‑pool misconfiguration, prompting a step‑by‑step performance investigation and multiple optimizations.
This article explains the Bridge design pattern, a structural pattern that separates abstraction from implementation to avoid class explosion, provides detailed Java code examples, UML diagrams, advantages, disadvantages, and typical scenarios for applying the pattern in software development.
This article evaluates the execution time and bytecode differences of simple and looped string concatenation in Java, comparing the '+' operator with explicit StringBuilder usage, and concludes that '+' is fine for single concatenations while StringBuilder dramatically outperforms '+' in iterative scenarios.
This article provides a comprehensive guide to designing and implementing a unified exception handling framework in Spring Boot, covering the use of @ControllerAdvice, custom assertion interfaces, enum‑based error codes, standardized response structures, and practical testing scenarios to improve code readability and robustness.
