This article presents a detailed Java learning roadmap covering fundamentals, core language features, the Spring framework, microservices, databases, DevOps tools, project experiences, and soft skills, guiding beginners to become proficient backend developers.
This article introduces mock testing for Spring MVC controllers, explains why mocks are useful, describes the main MockMvc components, shows required Maven dependencies, and provides complete example test cases for both view‑returning and JSON‑returning endpoints using JUnit and MockMvc.
This article explains the concept of streaming queries in MyBatis, describes the Cursor interface and its methods, demonstrates common pitfalls that cause cursor closure errors, and provides three practical solutions—using SqlSessionFactory, TransactionTemplate, or @Transactional—to keep the database connection open during iteration.
This article introduces the most commonly used Spring framework annotations—including core, MVC/REST, Boot, stereotype, data access, scheduling, and testing annotations—explains their purposes, usage scenarios, and provides Java code examples illustrating how to apply them in typical Spring applications.
A seasoned backend tech manager shares his journey from .NET to Java, exposing common interview traps—from misleading resumes and weak fundamentals to fierce market competition—and offers practical advice to help developers navigate career transitions successfully.
This article explains how to design a consistent JSON response structure for Spring-based micro‑service APIs, introduces a Result wrapper class, demonstrates annotation‑driven response handling, and shows controller, interceptor, and advice implementations to produce clean, maintainable backend responses.
This article examines whether Service and DAO layers in Java Spring projects should always have interfaces, discusses the arguments for and against using interfaces, and proposes practical structuring and dependency‑injection techniques to decide when interfaces are truly necessary.
This article provides a detailed tutorial on integrating Kafka with Spring using Spring‑Kafka, covering simple setup, embedded Kafka testing, topic creation, message sending and receiving, transaction support, listener configurations, manual acknowledgment, error handling, retry and dead‑letter queues, and related code examples.
This article provides a comprehensive guide to the Spring framework, covering its core modules, the concepts of Inversion of Control and Aspect‑Oriented Programming, various container implementations, proxy mechanisms, bean lifecycle, design patterns, MVC architecture, Spring Boot, Spring Cloud, and common annotations for Java backend development.
This article explains how Spring resolves circular dependencies for singleton beans using a three‑level cache, contrasts it with prototype limitations, provides a minimal container implementation that mimics the mechanism, and draws an analogy to the classic two‑sum algorithm to illustrate the core caching principle.
This article demonstrates how to create a Spring AOP request‑logging aspect that captures request parameters, response data, execution time, and error information, while also handling high‑concurrency scenarios and integrating traceId support for easier log tracing.
This article examines the drawbacks of lengthy if‑else statements in Java payment services, explains how they violate the Open/Closed and Single Responsibility principles, and presents multiple refactoring techniques—including custom annotations, dynamic bean naming, template methods, strategy‑factory, and chain‑of‑responsibility patterns—to produce cleaner, more maintainable backend code.
An in‑depth look at the latest Java Top‑200 project rankings reveals Spring’s ecosystem as the de‑facto standard, while contrasting tools such as Gradle versus Maven, Kafka versus Pulsar, Spring Security versus Shiro, and many others, highlighting performance, adoption and community strength across the backend landscape.
This article examines whether Service and DAO layers in Spring projects truly require interfaces, debunks common justifications, explores alternative project structures for single and multiple implementations, and offers practical guidelines on when to use or omit interfaces.
The author reflects on returning to Java after three years, arguing that despite the rise of containers and micro‑services, Java’s performance, threading model, and mature ecosystem keep it relevant, while criticizing Spring’s complexity and advocating a simple, KISS‑driven approach.
This guide explains the concepts, implementation steps, configuration examples, and key differences between Servlet Filters and Spring MVC Interceptors, helping developers choose the right tool for request preprocessing, logging, and access control in Java web applications.
This article explains what a circular dependency is in Spring, outlines the conditions under which Spring can resolve such cycles, and details the three‑level cache mechanism that enables bean creation, property injection, and AOP proxy handling to break the loop.
This article examines whether a Service layer in a Spring‑based backend project truly requires an interface, debunks common justifications, proposes practical development workflows, and outlines the advantages and drawbacks of using or omitting interfaces in various architectural scenarios.
This article explains the functional differences, recommended usage scenarios, and IDE warnings for Spring's @Autowired and @Resource annotations, showing how constructor, setter, and field injection affect code quality, testability, and framework portability.
This article explains the concept of streaming queries, introduces MyBatis's Cursor interface, demonstrates how to use it in Spring MVC controllers, and provides three concrete solutions—using SqlSessionFactory, TransactionTemplate, and @Transactional—to keep the database connection open and avoid cursor‑closed errors.
This article explains why Spring beans are not inherently thread‑safe, compares the singleton and prototype scopes, shows how stateless beans can be safe, demonstrates the impact of static fields and injected beans, and provides practical code examples and recommendations for achieving thread safety in Spring applications.
This article explores nine core design patterns implemented in Spring—simple factory, factory method, singleton, adapter, decorator, proxy, observer, strategy, and template method—detailing their implementation mechanisms, underlying principles, code examples, and practical significance for building loosely coupled, extensible Java applications.
This article examines whether a Service layer in a Spring‑based application truly requires an interface, analyzes common arguments for and against using interfaces, explores project structuring options, and offers practical recommendations based on real‑world development experience.
This article explains Spring Retry's architecture, how @EnableRetry, @Retryable, @Backoff and @Recover work together, details the available retry and back‑off policies, and walks through the core implementation using RetryTemplate and interceptors to provide flexible, AOP‑based retry handling in Java backend applications.
This article explains the fundamentals of Aspect‑Oriented Programming (AOP) in Spring, describes its core concepts and terminology, and provides step‑by‑step code examples for creating pointcuts, advices, and custom annotations, while also detailing the use of common AOP annotations such as @Pointcut, @Around, @Before, @After, @AfterReturning and @AfterThrowing.
This article shares practical techniques for handling large transactions in Spring-based backend systems, covering why @Transactional can cause issues, how to use programmatic transactions, move queries outside transactions, avoid remote calls, limit data volume, execute non‑transactional operations, and leverage asynchronous processing.
This article explains the concept of streaming queries in MyBatis, introduces the Cursor interface, demonstrates common pitfalls with connection closure, and provides three practical solutions—using SqlSessionFactory, TransactionTemplate, or @Transactional—to safely retrieve large result sets without exhausting memory.
This article explains how to configure Spring transaction isolation levels and propagation behaviors, illustrates the effects of dirty read, non‑repeatable read, and phantom read with examples, and provides practical code solutions for handling rollback of failed sub‑tasks and self‑invocation issues.
This article explains the real JDBC transaction methods, clarifies common misconceptions about transaction states in MyBatis, details the MyBatis Transaction and TransactionFactory interfaces, and explores special scenarios such as auto‑commit false, missing commit or close, with concrete code examples.
This article compares Spring and Spring Boot, explaining their fundamental concepts, Maven dependencies, MVC and security configurations, template engine setup, startup mechanisms, and packaging options, while providing practical code examples to help Java developers choose and migrate between the two frameworks.
This article explains the limits of annotation inheritance in Java, demonstrates why subclass methods cannot automatically inherit parent annotations, and shows how to use @Inherited, Spring's AnnotatedElementUtils, and find/get semantics to retrieve inherited annotations effectively.
The article explains how long‑running database transactions can exhaust connection pools, block threads, and cause widespread service failures, then offers practical strategies—including keeping transactions short, removing RPC calls, enhancing monitoring, and reviewing code—to detect and prevent these high‑risk issues.
This article provides a comprehensive overview of the Spring framework, explaining its IoC and AOP core, architectural layers, key advantages such as decoupling and declarative transactions, bean scopes, lifecycle settings, and practical object‑creation methods for Java backend development.
This article explains the AOP mechanism behind Spring's @Transactional, why only unchecked exceptions trigger automatic rollbacks, illustrates common pitfalls with code examples, and provides practical fixes such as using rollbackFor or manually marking the transaction for rollback.
This article explains how to create and use custom Java annotations together with Spring AOP to implement unified logging, method‑level parameter validation, and other cross‑cutting concerns, providing practical code examples and best‑practice recommendations for backend developers.
This article explains why Spring AOP advice does not trigger when a method calls itself via this, demonstrates how to reproduce the problem, and provides a solution using AopContext.currentProxy() together with proper proxy configuration to ensure the aspect executes correctly.
This article explains MyBatis-Plus's key features, shows how to add Maven dependencies, demonstrates the built‑in batch‑insert API, and provides step‑by‑step code to extend MyBatis‑Plus with a custom mapper and service for fast MySQL batch inserts.
This page continuously gathers and organizes over 200 Java backend interview Q&A articles, covering topics such as Spring, Redis, MySQL, concurrency, design patterns, and system design, providing a valuable resource for candidates to review before interviews.
This article demonstrates how to create a Spring AOP request‑logging aspect that captures request details, execution time, and errors, optimizes log output for high‑concurrency environments, and integrates trace‑ID tracking for easier debugging across distributed services.
This article explains how to create and use custom Java annotations in Spring for field validation, permission checks, and caching, including the definition of annotation types, associated validator and interceptor classes, and practical usage examples with code snippets.
Spring provides two IoC containers—BeanFactory and ApplicationContext—each with distinct loading strategies, features, and registration behaviors; this article demonstrates their differences through practical code examples, highlighting lazy versus eager loading, automatic post‑processor registration, and why ApplicationContext is generally preferred for enterprise applications.
By profiling the idle‑local Java backend, the author cut build, deployment, and startup times by over 30 seconds per cycle through asynchronous Spring bean initialization, selective dependency pruning, layered Docker image construction, and streamlined shutdown, demonstrating a comprehensive, reusable optimization strategy for faster releases.
This article examines whether every Service and DAO class in a Spring‑based backend should implement an interface, evaluates the common arguments for using interfaces, explains why they often do not hold up, and proposes practical structuring and development approaches for projects that may or may not need multiple implementations.
This article explains how ThreadLocal works internally, demonstrates its typical use in a Spring single‑sign‑on interceptor, analyzes the source code of ThreadLocal and ThreadLocalMap, and reveals the conditions under which ThreadLocal can cause memory leaks, offering practical guidance to avoid them.
This article explores why unit testing is essential, how to conquer the psychological obstacles that prevent developers from writing tests, and provides practical methodologies such as TDD, BDD, the test pyramid, and the Fixture‑Scenario‑Case pattern with concrete Java examples.
The article introduces Zheng, a full‑stack J2EE enterprise solution built on Spring, SpringMVC and Mybatis, detailing its modular microservice architecture, technology stack, module functions, environment setup, deployment tools, and provides links to the source repository and demo screenshots.
This article explains Java exception categories, distinguishing checked from unchecked exceptions, and shows how Spring's @Transactional annotation controls transaction rollbacks, including configurations for rolling back on checked exceptions, preventing rollback on unchecked ones, and best practices for applying @Transactional in backend services.
This article shares a developer's job‑search journey and detailed interview recap, covering project experience, Java collections, HashMap vs Hashtable, synchronized and volatile, singleton patterns, thread‑pool types, Spring Boot AOP, and Redis caching concepts, illustrated with diagrams.
Grails 4.0.5 has been released, introducing new features such as enhanced REST API configuration, plugin.groovy loading, performance optimizations, and updates to Micronaut, Spring, SpringBoot, and GORM Datastore, along with improved documentation and resolved issues.
This article explains the concept of read‑write splitting for databases, compares client‑side and proxy implementations, discusses data lag and forced routing techniques, and provides code examples and custom load‑balancing algorithms using Sharding‑JDBC and Spring.
This tutorial walks through the complete process of configuring a sandbox Alipay environment, setting up keys and URLs, defining the required database schema, and integrating Alipay payment flow into an SSM‑based Java backend with detailed code examples and troubleshooting tips.
This article explains the fundamental differences between Spring and Spring Boot, covering their core concepts, configuration methods, MVC setup, template engine integration, security configuration, bootstrapping mechanisms, and packaging/deployment options, with detailed code examples for each aspect.
This article explains how to create a consistent JSON response structure for Java backend APIs, covering status‑code conventions, a Result wrapper class, static helper methods, a custom @ResponseResult annotation, response‑body advice, and tips for simplifying controller code and handling exceptions.
This article provides a comprehensive, step‑by‑step guide to using programmatic transactions in Spring, covering both PlatformTransactionManager and TransactionTemplate approaches, complete with Maven configuration, SQL setup, test code, and best‑practice usage patterns.
This article compares Spring's programmatic and declarative transaction management, explains how each works with code examples, outlines the benefits and limitations of declarative transactions—including granularity and failure scenarios—and argues why developers should consider programmatic transactions for clearer control and fewer hidden bugs.
This article explains how Spring's @Enable annotations are driven by @Import, walks through the entry points in spring.handlers, details the processing flow of ConfigurationClassPostProcessor, distinguishes full and lightweight configuration modes, and describes the CGLIB enhancement that ensures proper @Bean method semantics.
This article provides a comprehensive overview of the most commonly used Spring Framework annotations, including core, stereotype, Spring Boot, MVC/REST, data access, scheduling, and testing annotations, with explanations and code examples illustrating their usage in Java backend development.
This article explains the Dependency Inversion Principle, shows why traditional layered architectures suffer from maintenance and reuse problems, provides concrete Java and web examples, and demonstrates how refactoring to abstract interfaces resolves these issues for more flexible, decoupled software design.
This article introduces Spring as a lightweight IoC and AOP container, explains Spring MVC as its web framework, describes Spring Boot's convention‑over‑configuration approach to simplify setup, and outlines how Spring Cloud builds on Spring Boot to provide micro‑service governance.
This page provides a comprehensive collection of links to over a hundred interview‑focused articles covering Java, Spring, Redis, MySQL, concurrency, design patterns, and other backend development topics, organized by issue number for easy reference.
This tutorial walks through the complete process of configuring a sandbox Alipay environment, setting up keys and URLs, defining the database schema, implementing DAO and service layers, and integrating Alipay payment flow into a Java SSM project with detailed code examples and screenshots.
This article walks through the Spring Framework container startup process, explaining how the AnnotationConfigApplicationContext constructor prepares the environment, registers readers and scanners, initializes the BeanFactory, sets up condition evaluators and post‑processors, and outlines the default filters used for component scanning.
This article explains how to define custom Java annotations for field, method, and class validation, demonstrates the required @Target and @Retention settings, shows how to implement a ConstraintValidator, and provides practical Spring examples for permission checks and caching using interceptors and aspects.
This article explains the core ideas of Java reflection, demonstrates how to obtain Class objects, create instances, access fields and methods, and discusses common use cases such as Spring IoC, factory patterns, and JDBC driver loading, while also covering its advantages, drawbacks, and best‑practice tips.
This article explains how Spring WebFlux, built on the Reactor project, provides a reactive, non‑blocking alternative to traditional Servlet‑based Spring MVC, detailing its advantages, limitations, and the considerations developers must evaluate before adopting it.
This article explains the three common factory design patterns—simple factory, factory method, and abstract factory—illustrates their Java implementations with product and factory classes, demonstrates client usage, and shows how Spring's dependency injection can replace manual factory instantiation, providing a comprehensive guide for developers.
This article explains the core interfaces of the Spring Framework, such as BeanDefinition, BeanFactory, ApplicationContext, and BeanPostProcessor, and walks through the bean creation process—including refresh, preInstantiateSingletons, getBean, and the three‑level singleton caches—providing detailed code examples and insights into how Spring resolves circular dependencies.
Learn how Spring stores bean metadata, the structure of BeanDefinition, naming conventions, alias configuration, and various bean instantiation methods—including constructors, static and instance factory methods—while also discovering how to determine a bean's runtime type using BeanFactory.getType.
This article introduces the open‑source Spring framework for Java, explains the core concepts of Inversion of Control (IOC) and Aspect‑Oriented Programming (AOP), and walks through creating a Spring Boot web project with MVC layers, annotations, and a runnable example.
This article explains how to use Spring's event‑driven mechanism to decouple business operations such as saving a product and sending notifications, showing step‑by‑step code for custom events, publishing, asynchronous listeners, and custom thread‑pool configuration to improve resilience and maintainability.
This article explains the essential design principles of a TCC (Try‑Confirm‑Cancel) distributed transaction framework, covering the necessity of RM local transactions, integration with Spring's TransactionManager, fault‑recovery mechanisms, idempotency guarantees, and handling of parallel Try/Confirm/Cancel operations.
This article explains the concept of AOP, its typical use cases, the underlying mechanisms of Spring AOP (JDK dynamic proxy and CGLIB), the relationship with AspectJ, and provides a complete XML‑free code example that demonstrates aspects, pointcuts, join points and advice.
This article explains the Template Method design pattern, illustrating its structure with Java code examples—including an abstract Drinks class, concrete Tea and Coffee subclasses, hook methods, and real‑world usages in JDK sorting and Spring's application context—while highlighting advantages, drawbacks, and typical scenarios.
This article explains the concept of circular dependencies in Spring, reviews related fundamentals, demonstrates how Spring's three-level cache resolves singleton circular references, discusses limitations with prototype and constructor injection, and provides code examples and detailed source analysis for developers.
This article explains how Spring's @Transactional annotation works, common pitfalls such as using it on private methods, and the correct ways to configure propagation, isolation, and bean injection to ensure proper transaction rollback and non‑rollback behavior.
SpringBoot supports internationalization out of the box; by creating a messages.properties file under resources, configuring the basename in application.yml, and using a MessageUtils wrapper that retrieves MessageSource via SpringUtils, developers can fetch localized messages with a single method call.
This article explains how to accelerate service response by integrating Redis as a key‑value cache with Spring Cache, covering the three‑step implementation, required Maven dependencies, XML configuration, property settings, a custom Cache implementation class, and common Spring Cache annotations.
This article provides a comprehensive guide to Spring Validation, covering basic usage, dependency setup, requestBody and requestParam validation, group and nested validation, collection checks, custom constraints, programmatic validation, fail‑fast configuration, and the underlying implementation mechanisms within Spring MVC and Hibernate Validator.
This article dives deep into Spring's transaction infrastructure, explaining how @EnableTransactionManagement activates transaction support, detailing the roles of key configuration classes, core interceptors, transaction attribute resolution, propagation behaviors, and the commit‑and‑rollback processes that power reliable data operations in Spring and Spring Boot applications.
This article presents a Java FTP utility class designed for Spring applications, detailing its implementation as a bean, configuration via properties, and methods for uploading, downloading, and deleting files on an FTP server, along with common troubleshooting tips and usage examples.
This article provides a thorough tutorial on Spring Validation, covering basic usage with requestBody and requestParam, dependency setup, group, nested, collection and custom validations, programmatic validation, fail‑fast mode, differences between @Valid and @Validated, as well as the underlying implementation mechanisms in Spring MVC and method‑level AOP validation.
This article explains how to design and implement custom Java annotations for field validation, permission checks, and caching, covering annotation definitions, target and retention policies, validator classes, interceptor and aspect implementations, and practical usage examples within Spring MVC.
This article explores Spring’s @Async annotation in depth, detailing its basic usage, underlying proxy creation, pointcut logic, and asynchronous execution, while highlighting common issues such as circular dependencies and inefficient default thread pools, and providing practical solutions like lazy injection and custom executors.
This article explains Spring's bean scopes, compares singleton and prototype beans regarding thread safety, demonstrates the issue with shared state through code examples, and provides practical solutions such as using prototype scope or ThreadLocal to avoid concurrency problems.
This article explains several ways to implement scheduled tasks in Java, covering the simple Timer class, the more robust ScheduledExecutorService, Spring's @Scheduled annotation, and distributed solutions using Redis ZSet and key‑space notifications, with code examples and practical considerations.
Spring MVC controllers are singleton by default, which can cause thread‑unsafe behavior when using non‑static member variables; this article demonstrates the issue with example endpoints, shows how prototype scope resolves it, and outlines best practices such as avoiding stateful fields or using ThreadLocal.
This page provides a comprehensive list of over 150 Java interview question articles, covering topics such as collections, concurrency, JVM, databases, Redis, Spring, and system design, organized by issue numbers for easy reference.
This article explains Spring's circular dependency problem, the conditions under which it can be resolved, and how Spring's three‑level cache—combined with AOP proxy handling—enables beans to reference each other without causing creation failures, providing a comprehensive answer for interview scenarios.
This article explains why Spring MVC controllers are singleton by default, demonstrates the thread‑safety issues caused by shared instance variables, shows how to test the behavior with sample code, and presents solutions such as using prototype scope, avoiding member variables, or employing ThreadLocal.
This article explains the differences between Spring's @Validated and the standard @Valid annotations, covering grouping support, where each can be applied, and how to enable nested validation for complex objects in controller parameters.
This article explains Java exception classifications, how Spring's @Transactional handles checked and unchecked exceptions, and provides practical configurations to control transaction rollbacks, while offering best‑practice notes on annotation placement and method design.
This guide explains Java exception classification, the default rollback behavior of Spring's @Transactional annotation, and how to configure rollback for checked and unchecked exceptions while offering best‑practice recommendations for transactional method design.
This article analyzes a severe overselling incident caused by an unsafe Redis distributed lock during a high‑traffic flash‑sale, explains the root causes, and presents safer lock and atomic stock‑decrement solutions with improved Java code examples.
This article explains the differences between Apache BeanUtils and Spring BeanUtils for copying Java objects, covering shallow vs deep copy concepts, performance drawbacks of Apache's implementation, usage examples, and recommendations for alternative tools like CGLIB BeanCopier and Orika.
A Java Spring service method misused map.contains and REQUIRES_NEW transaction propagation, leading to unreleased DB connections and a CannotCreateTransactionException, and the article walks through the bug, its root causes, and concrete fixes including correct key checks and timeout settings.
The article explains why Spring MVC controllers are singleton by default, demonstrates the resulting thread‑unsafe behavior with example code, shows how applying @Scope("prototype") makes them prototype scoped, and provides best‑practice recommendations and a summary of Spring bean scopes.
This article provides a comprehensive explanation of Spring's @EnableAsync and @Async annotations, covering their purpose, usage steps, handling of return values, custom thread‑pool configuration, exception handling, thread‑pool isolation, and the underlying AOP mechanism, supplemented with complete code examples.
The article examines a Spring‑related Twitter poll, Google Trends, and Stack Overflow statistics to compare MyBatis, Hibernate, and JPA, then argues that MyBatis’ simplicity and flexibility make it better suited for today’s fast‑paced backend development.
This article explains the internal workflow of Spring's annotation processing, detailing how @Component and its specializations like @Service are discovered through XML namespace handlers, classpath scanning, metadata readers, and meta‑annotation handling, complete with code excerpts and step‑by‑step analysis.
This article explains how to copy properties between Java objects, clarifies shallow and deep copy concepts, compares Apache BeanUtils and Spring BeanUtils with code examples, and advises on performance and best‑practice choices for backend development.
