This article explains how to implement runtime switching of multiple service providers in a Spring‑based backend by configuring the active implementation in a central store and using the spring‑smart‑di library's AutowiredProxySPI to inject the appropriate bean automatically.
This article explains why overusing Spring's @Autowired can lead to hidden dependencies, tight coupling, NullPointerExceptions, and testing difficulties, and demonstrates how constructor injection provides clearer, safer, and more test‑friendly dependency management.
This article explains critical pitfalls and best‑practice guidelines for employing Spring Event in Java backend applications, covering graceful shutdown requirements, event loss during startup, suitable business scenarios, reliability enhancements, retry mechanisms, idempotency, and the relationship between Spring Event and message queues.
This article explains how to automatically embed userId and orderId into log statements by defining log placeholders, storing these values in MDC via ThreadLocal, and using a custom @UserLog annotation together with Spring AOP to inject the data before method execution, complete with configuration and test examples.
This article explains how Spring AOP creates proxies using JDK dynamic proxies or CGLIB, outlines the limitations of each approach, and shows multiple ways—including XML, YAML, and annotations—to force CGLIB usage and resolve self‑invocation issues in Spring Boot applications.
An extensible asynchronous processing SDK is presented, leveraging Spring transaction events, Kafka queues, XXL‑Job scheduling, and a non‑intrusive architecture to ensure high performance, data safety, and eventual consistency while simplifying integration across Java backend services.
This article explains how to build a scalable, maintainable permission control framework in Java by defining custom annotations, designing relational database tables, and using Spring AOP to intercept method calls for organization‑level, personal, limit, and special‑role checks, while providing implementation details and best‑practice recommendations.
This article explains how to leverage Spring's TransactionSynchronizationManager to detect active transactions and register synchronization callbacks so that Kafka messages are sent asynchronously only after a transaction successfully commits, ensuring data consistency without impacting the main business flow.
This article provides a comprehensive overview of Spring's built‑in utility classes—including assertion, string, collection, object, file/resource, web, reflection, AOP, path‑matching, and ID generation helpers—illustrating their usage with code examples and highlighting how they improve development efficiency and code quality.
This article presents a detailed overview of Spring's utility classes—including Assert, ObjectUtils, StringUtils, CollectionUtils, FileCopyUtils, ResourceUtils, StreamUtils, ReflectionUtils, and AOP helpers—provides code examples for each, and also contains promotional information about ChatGPT services and a developer community.
A deep dive into Spring Event's delayed listener registration reveals how messages can be lost during the brief window between Kafka consumer initialization and EventListener setup, explaining the root cause, illustrating the startup order, and recommending safer alternatives for reliable message handling.
This article explains the Chain of Responsibility design pattern, demonstrates its application in a product creation workflow with concrete Java code, shows how to configure and assemble handlers dynamically using Spring, and discusses the pattern's advantages, drawbacks, and testing scenarios.
This article explains how to replace repetitive try‑catch blocks in Java backend development with a unified exception handling approach using Spring's @ControllerAdvice, custom Assert utilities, and enum‑based error codes, providing cleaner code, consistent error responses, and easy internationalization.
This article explains why Spring transactions may fail, demonstrates simple examples with and without the @Transactional annotation, details the annotation’s definition and attributes, and provides a step‑by‑step source‑code analysis of transaction creation, commit, rollback, and cleanup in Spring 4.3.12.
This article explains why API debouncing is crucial for backend Java services, outlines which endpoints need protection, describes how to identify duplicate requests, and provides step‑by‑step implementations using Redis shared‑cache and Redisson distributed locks with concrete code examples and test results.
This article explains Spring's three dependency injection methods—constructor‑based, setter‑based, and field‑based—illustrates each with code examples, discusses why field injection is discouraged, and recommends using constructor injection for required dependencies and setter injection for optional ones.
This article provides a detailed tutorial on the Activiti 7 workflow engine, covering workflow concepts, BPMN modeling, environment configuration, Maven dependencies, database schema creation, deployment methods, process instance management, task handling, and historical data querying, with complete code examples for Java developers.
This article explains how Spring 3.0's pure annotation mode simplifies bean configuration, demonstrates using @Component, @Scope, @Autowired, @Qualifier, @Value, and @PropertySource for dependency injection and property loading, and shows step‑by‑step integration of MyBatis with Spring, including required dependencies and configuration classes.
Fast‑Retry is a high‑performance Java framework that enables asynchronous, multi‑task retries with both programmatic and annotation‑based APIs, dramatically improving throughput for large‑scale retry scenarios compared to traditional synchronous retry libraries.
The article explains how to leverage Spring's TransactionSynchronizationManager to detect active transactions and register synchronization callbacks that asynchronously send Kafka messages after a transaction commits, ensuring reliable fund‑flow archiving in payment systems while avoiding thread‑switch issues.
Spring WebClient, the reactive replacement for the deprecated RestTemplate in Spring 5+, offers non‑blocking I/O, functional style, streaming support, and improved error handling; this article explains its benefits, demonstrates synchronous and asynchronous request patterns, timeout configuration, and comprehensive error processing with code examples.
This article explains how to use Spring's TransactionSynchronizationManager to detect active transactions and register synchronization callbacks that asynchronously send Kafka messages only after a transaction commits, illustrated with a payment‑system case and complete Java code examples.
This article explains why RestTemplate is deprecated in Spring Framework 5+, outlines the advantages of the reactive WebClient such as non‑blocking I/O, functional style, streaming and improved error handling, and provides complete Java code examples for creating, configuring, and using WebClient synchronously and asynchronously, including timeout and error management.
This article explains how to enable cross‑node WebSocket communication in a distributed Spring application by using a message queue (Redis or Kafka) to broadcast messages, tracking user connections with Redis, and providing a complete step‑by‑step implementation with code samples and configuration details.
This article demonstrates how Lombok annotations such as @RequiredArgsConstructor, @Delegate, @Cleanup, @Singular, and @Builder can be combined with Spring components to reduce boilerplate, automatically inject dependencies, manage resources, and build immutable objects, providing practical code examples and usage guidelines.
This article outlines how to correctly create, monitor, and configure Java ThreadPoolExecutor instances, explains why using the Executors factory can cause OOM, recommends separate named pools per business, provides formulas for sizing CPU‑bound and I/O‑bound workloads, and highlights real‑world pitfalls and dynamic‑configuration solutions.
This article explains why traditional programmatic HTTP clients cause duplicated, hard‑to‑maintain code in enterprise projects, introduces the UniHttp declarative framework with its annotations, shows a quick‑start guide, details lifecycle hooks for custom processing, and demonstrates an enterprise‑level weather‑service integration example.
This article presents fourteen practical Java Spring development best‑practice tips—including using @ConfigurationProperties, Lombok's @RequiredArgsConstructor, modularizing code, throwing exceptions instead of returning error codes, minimizing unnecessary database calls, avoiding null returns, reducing if‑else chains, and leveraging IDE features—to help developers write cleaner, more maintainable backend code.
This article explains how to leverage Spring's TransactionSynchronizationManager to detect active transactions, register synchronization callbacks, and asynchronously send Kafka messages only after a transaction successfully commits, providing a practical example and detailed code snippets for building a reusable Spring Boot starter library.
This article demonstrates how to build a hot‑pluggable AOP solution in Spring by dynamically adding and removing Advice, Advisor, and related components through custom endpoints, event listeners, and Spring’s bean factory APIs, enabling users to control logging at runtime.
An in‑depth guide reveals thirteen common pitfalls that cause Spring’s @Transactional annotation to malfunction—ranging from unnecessary usage and proxy limitations to propagation misconfigurations and exception handling—plus practical demos and solutions to ensure reliable transaction rollbacks in Java backend development.
This article explains how to handle time‑consuming Spring endpoints by using asynchronous streaming tools—ResponseBodyEmitter, SseEmitter, and StreamingResponseBody—detailing their use cases, code examples, and how they improve system responsiveness without blocking servlet threads.
This article, written by a senior architect, reviews Spring’s built‑in utility classes—including assertions, object and collection helpers, file/IO operations, and reflection/AOP tools—providing code snippets and usage notes to help developers replace redundant custom utilities and improve backend Java code quality.
This article analyzes the performance differences between native Java reflection and Spring Framework's ReflectionUtils by running benchmark tests, examining source code caching mechanisms, and explaining why ReflectionUtils can be faster for repeated method and field access in backend applications.
This article explains how to use Spring's TransactionSynchronizationManager to detect active transactions, register synchronization callbacks, and asynchronously publish payment‑log messages to Kafka without affecting the main business flow, complete with practical code snippets and pitfalls to avoid.
This article explains how Spring’s ResponseBodyEmitter, SseEmitter, and StreamingResponseBody can be used to build asynchronous streaming endpoints that continuously push data to clients, avoid servlet thread blocking, and prevent request‑timeout problems, with complete code examples and usage guidelines.
This article walks through a systematic investigation of a slow‑starting Dubbo service built on Spring 3.2, using JProfile to pinpoint costly class‑loading checks, disabling unnecessary annotation processing, and resolving thread‑waiting issues caused by RabbitMQ and other components, ultimately reducing deployment time by about 40%.
The article explains how to simplify Spring MVC controller code by introducing a unified response wrapper, handling String return types with ResponseBodyAdvice, adjusting HttpMessageConverter order, applying JSR‑303 validation for @RequestParam, @PathVariable and @RequestBody, creating custom validation annotations, and implementing global exception handling for consistent API responses.
This article explains Java's built‑in Service Provider Interface (SPI) mechanism, demonstrates how to implement and test SPI with sample code, analyzes its internal workings and limitations, and then shows how Spring extends SPI using spring.factories with comparable examples and source‑code insights.
This article dissects the exact moment a Spring @Transactional method commits relative to a surrounding lock, explains why committing after unlock can cause overselling, and provides source‑level debugging techniques to verify transaction start, commit, and rollback behavior in MySQL under high concurrency.
This article explains how to implement runtime switching of multiple service providers, such as SMS vendors, in a Spring-based backend using the spring‑smart‑di library, @EnvironmentProxySPI, and @AutowiredProxySPI annotations, with configuration stored in Nacos, databases, or environment variables.
This article explains how to design and implement a fixed-size FIFO export queue in a Java backend using Spring components and EasyExcel, covering business requirements, class definitions, code examples, testing results, and considerations for further enhancements such as Redis queues and high‑concurrency scenarios.
This article explains how to automatically include userId and orderId in log messages by storing them in MDC, defining a custom @UserLog annotation, and using Spring AOP to inject the values at runtime, eliminating manual log parameter handling.
This article explains the State design pattern, demonstrates its Java implementation with example code, introduces Spring State Machine concepts, and provides a complete step‑by‑step guide to building and testing an order status workflow using Spring State Machine, including configuration, listeners, services, and a controller.
The article describes a Java‑based FIFO export queue that limits concurrent MySQL export operations, outlines the related classes (ExportQueue, AbstractExport, ExportImpl, and a test controller), provides full source code, and presents test results showing how the queue manages up to ten simultaneous export requests.
This article walks through the eight critical phases of a Spring bean's lifecycle—from instantiation and property population to initialization, post‑processor hooks, usage, and destruction—detailing how Spring creates, configures, enhances, and finally disposes of beans, with code snippets and diagrams for clarity.
The article recounts a production incident where Spring Event caused bean‑lookup failures during service shutdown, explains the three‑step usage of Spring Event with code examples, and presents three mitigation strategies—abandoning Spring Event, handling exceptions with MQ retries, and implementing graceful shutdown—ultimately opting to drop Spring Event.
This article explains the concept of request debouncing, identifies which API endpoints need it, and demonstrates two distributed lock solutions—shared Redis cache and Redisson—by providing complete Java code examples, configuration steps, and test results to prevent duplicate submissions in backend services.
Fast‑Retry is a high‑performance, multi‑task asynchronous retry framework for Java that dramatically outperforms traditional synchronous retry libraries like Spring‑Retry and Guava‑Retry, especially when handling millions of tasks, by leveraging non‑blocking execution, customizable strategies, and seamless Spring integration.
This article explains how to create a custom annotation and MyBatis‑Plus interceptor to enforce data‑permission filtering based on user roles, provides both basic and advanced implementations with complete Java code examples, and shows how to integrate the interceptor into the MyBatis‑Plus plugin configuration.
This article explains the Inversion of Control principle, defines what an IOC container is, compares Spring’s BeanFactory and ApplicationContext, and walks through the three-stage startup process—including loading configurations, registering bean definitions, and instantiating beans with automatic dependency injection.
This article demonstrates how to automatically embed userId and orderId into Java log statements by defining log placeholders, storing these values in ThreadLocal and MDC, and using a custom @UserLog annotation together with Spring AOP to inject the context without manual code changes.
This article presents a comprehensive collection of frequently used Spring framework utility classes—including Assert, ObjectUtils, StringUtils, CollectionUtils, FileCopyUtils, ResourceUtils, ReflectionUtils, and AopUtils—explaining their purpose, typical use cases, and providing code snippets for each method to help developers avoid redundant implementations.
This article explains the most common reasons why Spring @Transactional annotations may become ineffective or fail to roll back, covering access‑modifier issues, final methods, internal calls, self‑injection, multithreading, unsupported table engines, mis‑configured propagation, exception handling, nested transactions, large‑transaction problems, and the advantages of programmatic transaction management.
This article demonstrates how to leverage Spring's TransactionSynchronizationManager to detect active transactions and register synchronization callbacks that asynchronously publish payment ledger messages to Kafka after transaction commit, while providing a starter-style library for easy integration.
This article explains the callback pattern in Java, compares synchronous and asynchronous callbacks, shows how to implement them with interfaces, anonymous classes, and Lambda expressions, and demonstrates practical uses in Spring bean factories and data‑processing pipelines.
This article explains how to enable cross‑server WebSocket communication in a distributed Spring application by using a message queue such as Redis or Kafka, detailing two architectural approaches, concrete code examples, configuration files, and a sample client page.
The article explains how to solve interleaved multi‑thread logs in micro‑services by adding a X‑App‑Trace‑Id header, extracting it in a TraceIdFilter, storing it in SLF4J MDC, propagating it through Feign, adapting it for child threads, and finally integrating SkyWalking to print both application and SkyWalking trace IDs in Logback.
This article explains how to correctly manage transactions across multiple threads in a Spring application by using manual SqlSession control, providing utility methods for list partitioning, thread‑pool configuration, and example code that demonstrates both failing and successful transaction scenarios.
Spring offers multiple HTTP clients—RestTemplate, WebClient, and the newer RestClient—each with distinct features, performance characteristics, and suitability for different scenarios, and this guide compares their core capabilities, advantages, drawbacks, and best-use cases to help developers select the optimal client for their projects.
This article explains why Spring transactions can become ineffective or fail to roll back, covering issues such as wrong method visibility, final methods, internal calls, missing Spring bean registration, multithreading, unsupported table engines, misconfigured propagation, exception handling, and offers practical solutions for each case.
This article explains how to let users upload a JAR containing a custom implementation of a predefined Java interface, then hot‑deploy the JAR by loading it with a URLClassLoader and dynamically registering or deregistering Spring beans using reflection or annotation modes.
This article presents fourteen practical Java backend optimization techniques—including configuration‑file management, Lombok’s @RequiredArgsConstructor, modular code design, exception handling, reducing DB queries, avoiding null returns, minimizing if‑else, slimming controllers, IDE shortcuts, source‑code reading, design patterns, and efficient collections—each illustrated with clear code examples.
This article provides an in‑depth technical analysis of Spring StateMachine's internal architecture, covering its class hierarchy, lifecycle start/stop mechanisms, pseudo‑state types, trigger processing, event dispatching, and persistence strategies, all illustrated with concrete code examples.
This article systematically catalogs every Spring and Spring Boot extension interface—from ApplicationContextInitializer to DisposableBean—illustrates their invocation order with a diagram, explains practical use‑cases, and provides concrete code samples for each hook, enabling developers to tap into the bean lifecycle for custom initialization, monitoring, and cleanup.
Recent disclosures revealed critical Spring DoS flaws (CVE‑2024‑38809 and CVE‑2024‑38808) exploitable via oversized If‑Match/If‑None‑Match headers and malicious SpEL expressions, plus a Nacos 2.4.1 vulnerability allowing arbitrary file read/write through port 7848, mitigated by upgrading to the patched Spring and Nacos releases or restricting the vulnerable ports.
This article explains how to replace repetitive try‑catch blocks in Java backend code with a unified exception handling mechanism based on Spring's @ControllerAdvice, custom Assert utilities, and error‑code enums, resulting in cleaner, more maintainable services and controllers.
This article reviews the most popular Java frameworks for 2024, explaining their purpose, key features, and how they help developers build scalable, secure, and efficient web applications across various industries.
This article provides a concise yet comprehensive guide to the most common SpringBoot annotations—including @SpringBootApplication, @EnableAutoConfiguration, @ComponentScan, @Service, @Repository, @Component, @RestController, @Bean, @ResponseBody, and @Autowired—explaining their purpose, composition, and practical code examples for building robust Java backend applications.
This article analyses thirteen common mistakes that cause Spring's @Transactional annotation to be ineffective or not roll back, covering unnecessary usage, private/final/static methods, self‑invocation, wrong propagation settings, async threads, unmanaged beans, exception handling and more, with concrete code demos and solutions.
The guide equips candidates for backend interviews by covering essential networking (HTTP/HTTPS, TLS handshake, status codes, headers, OCSP, session resumption, CSRF), RPC frameworks, Java class-loading and JVM memory/GC, OS process/thread scheduling, Spring bean lifecycle, Redis caching pitfalls, and MySQL indexing and query optimization.
This course provides an in‑depth exploration of the technical challenges faced by Java architects, covering Spring bean lifecycle, AOP, transaction mechanisms, SpringBoot auto‑configuration, JVM memory models, MySQL indexing, Redis caching, microservice patterns, distributed locks, and performance optimization techniques across 99 video modules.
This article introduces eight common Java asynchronous implementation techniques—including raw threads, Future, CompletableFuture, Spring @Async, ApplicationEvent, message queues, third‑party utilities like Hutool ThreadUtil and Guava ListenableFuture—explaining their usage, code examples, advantages, and drawbacks for improving performance in scenarios such as sending SMS or emails.
This article explains how to implement interface debounce in Java backend services, covering the concept, identifying suitable APIs, generating unique keys, and applying distributed locking mechanisms with Redis and Redisson, including code examples and practical testing results.
This article explains how to design a clean, unified API response format for backend services by defining a standard JSON wrapper, categorizing status codes, adding descriptive messages, and using custom @ResponseResult annotations together with interceptors and controller advice to automatically wrap and handle responses in a Spring‑based application.
On his first day the new Java backend developer discovered duplicated internal and external configuration files causing NullPointerExceptions, hard‑coded role strings, mixed System.out and logger calls, missing manager review leading to DB mismatches, arbitrary production database edits, and Maven pom‑type dependency errors, prompting a shift to unified application.yml settings, JVM‑specified config locations, consistent logging, and stricter coding standards.
This article explains how Lombok's @RequiredArgsConstructor can replace repetitive @Autowired field injections in Spring services by generating a constructor for final fields, demonstrates the underlying annotation‑processing mechanism, and provides practical code examples for applying this technique in backend Java projects.
This article explains how to leverage Spring's TransactionSynchronizationManager to detect active transactions, register synchronization callbacks, and asynchronously send Kafka messages after transaction commit, providing a starter library design for Java backend services that need reliable transaction‑aware messaging.
This article explains how to use the Strategy pattern combined with a simple factory in a Spring‑based Java backend, showing interface definition, multiple arithmetic strategy implementations, a factory that registers them in a map, a service that selects a strategy at runtime, and a REST controller for testing.
This article explains how Spring's @Async annotation interacts with circular dependencies, why it triggers BeanCurrentlyInCreationException, and provides multiple strategies—including adjusting dependencies, using @Lazy, or tweaking bean factory settings—to solve the problem.
The article explains why adopting a message‑queue improves microservice decoupling and responsibility boundaries, then details the design of a pluggable Base‑MQ component—including @MQEventListener, MQEvent base class, configuration, and MQClient interface—followed by concrete implementations for RocketMQ, Kafka, Redis and RabbitMQ, an example event flow, and guidance for extending the framework.
This article analyzes recent critical security flaws in Spring Framework (CVE‑2024‑38808 and CVE‑2024‑38809) and Nacos Jraft port, explains their impact, provides version‑specific mitigation steps, code snippets for Spring Boot fixes, and offers additional hardening recommendations for developers and operators.
This article clarifies how Inversion of Control (IoC) serves as a design pattern that hands control to an external container, while Dependency Injection (DI) is a concrete IoC implementation that automatically supplies required objects, detailing their definitions, purposes, implementations, and typical usage scenarios.
This article explains critical pitfalls, proper shutdown handling, event loss during startup, suitable business scenarios, reliability guarantees, and best‑practice patterns for employing Spring Event in high‑traffic backend systems, providing concrete code examples and operational recommendations.
This article explains the design, advantages, and implementation details of a generic asynchronous processing SDK that leverages Spring transactional events, Kafka messaging, XXL‑Job scheduling, and a non‑intrusive architecture to ensure data consistency, fault tolerance, and easy integration across services.
The article explains that Spring no longer recommends @Autowired field injection, describes constructor‑based, setter‑based, and field‑based dependency injection types, illustrates each with code examples, and outlines the drawbacks of field injection such as immutability issues, SRP violations, and tight coupling to the container.
This article explains how using Spring's @Transactional annotation together with explicit locks can cause unexpected concurrency issues, demonstrates the problem with sample code, analyzes why the lock becomes ineffective, and presents solutions such as separating transactional methods, using programmatic transactions, or locking the entire transaction.
Fast‑Retry is a high‑performance Java library that enables asynchronous, multi‑task retry with customizable logic, offering a scalable alternative to synchronous retry frameworks like Spring‑Retry and Guava‑Retry for handling massive workloads such as millions of user identity queries.
The article explains why Spring discourages field injection, compares constructor, setter, and field injection types, provides Java code examples, and outlines the drawbacks of field injection such as immutability issues, SRP violations, container coupling, and hidden dependencies.
This article explains how to quickly test MyBatis SQL statements by bypassing the Spring container, using a minimal MyBatis configuration, adding support for PageHelper pagination and MyBatis‑Plus plugins, and provides code examples and a plugin recommendation for efficient backend development.
This article describes a Java‑based asynchronous processing SDK that leverages Spring AOP, transactional event listeners, Kafka, XXL‑Job, and MySQL to provide non‑intrusive, reliable, and eventually consistent background execution of business methods while preserving transaction integrity and offering configurable retry and compensation strategies.
This article presents fourteen actionable techniques for improving Java backend code quality, including using configuration files, Lombok's @RequiredArgsConstructor, modular design, exception handling, reducing unnecessary database calls, avoiding null returns, simplifying if‑else logic, minimizing controller logic, leveraging IDE features, reading source code, applying design patterns, embracing new knowledge, mastering fundamentals, and efficiently checking element existence, supplemented with concrete code examples.
This article explains how to refactor Spring MVC controller layers by introducing a unified response wrapper, handling String conversion issues with ResponseBodyAdvice, applying JSR‑303 validation for request parameters, creating custom validation annotations, and implementing custom exceptions with a global exception handler to produce clean, maintainable backend code.
This article explains how to build a clean, maintainable Controller layer in Spring by separating responsibilities, unifying response structures, applying global response wrapping, leveraging JSR‑303 validation for parameters, creating custom validation rules, and handling exceptions uniformly, all illustrated with practical Java code examples.
This article explains how Spring 3.0's pure annotation development simplifies bean configuration, demonstrates defining beans with @Component, managing bean scopes, performing various injection techniques, reading properties files, and integrating MyBatis, providing complete code examples and best‑practice tips for backend Java developers.
This tutorial explains how Spring's pure annotation mode replaces XML bean definitions, covers component scanning, bean scopes, dependency injection techniques, property loading, and demonstrates seamless integration with MyBatis for streamlined backend development.
This article explains how Spring’s pure annotation development replaces XML bean definitions, covers component scanning, bean scopes, derived annotations, various injection methods, property file loading, and demonstrates seamless Spring‑MyBatis integration, showing step‑by‑step code examples that simplify backend configuration.
This article explores the subtle timing of Spring transaction start and commit relative to lock/unlock, demonstrates how improper ordering can cause over‑selling in high‑concurrency scenarios, and provides debugging techniques and practical solutions to ensure atomicity and correct rollback behavior.
This article explains how to prevent duplicate API submissions by applying debounce principles and implementing distributed locks using Redis and Redisson in a Java Spring backend, providing detailed code examples, key generation strategies, and practical testing results.
This guide walks through Spring Cloud Gateway features—including marking exchanges as routed, enabling route metrics, configuring metadata, accessing Reactor Netty logs, troubleshooting with debug logging, disabling automatic route refresh, ordering global filters, using Actuator sub‑paths, and rewriting request parameters—complete with code snippets and configuration examples.
