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hanweiwei

@hanweiweiJoined December 2024

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Java corehanweiwei.hashnode.dev9 posts Reason Behind URL Length Limitsreason-behind-url-length-limits.hashnode.dev1 post

hanweiwei.hashnode.devDec 11, 2025 · 6 min read

Enhancing Bean Validation Messages with Spring AOP: Injecting the Original Value

The Java Bean Validation API (JSR 380, often implemented by Hibernate Validator) provides a robust way to validate data. While the default mechanism for constraint violation messages is adequate, developers often face a common need: including the ori...

hanweiwei.hashnode.devJun 3, 2025 · 2 min read

Java Lambda 表达式

1. 背景 Java 8 引入了 Lambda 表达式和函数式接口，其基础技术是 invokedynamic 指令和 LambdaMetafactory 动态类生成机制。相比于传统的匿名内部类和反射，它具有更好的性能和编译器可分析性。（对于编译器跟JVM虚拟机来说，对于确定性的内容更容易优化，比如内联、分支预测、逃逸分析等等） 2. Lambda 是如何被实现的？ int num = 10; Runnable r = () -> System.out.println(num);//Lambda语...

hanweiwei.hashnode.devJun 3, 2025 · 2 min read

Java 泛型中的协变与设计原则冲突

协变逆变（Covariance and Contravariance: Conflict without a Cause）设： A 和 B 是类型（types）； f 是一个类型变换器（type constructor / type transformation），例如 f(T) = List<T>； ≤ 表示子类型关系（subtyping relation），即 A ≤ B 表示 A 是 B 的子类型（即 A <: B）。那么：协变（Covariant）：如果 A ≤ B，则...

hanweiwei.hashnode.devMay 30, 2025 · 3 min read

Analysis of Covariance in Java Generics and Conflicts with Design Principles

In Java's generic system, covariance refers to the ability to use a subtype generic where a supertype generic is expected, typically expressed through ? extends T. For example: List<? extends Number> numbers = new ArrayList<Integer>(); Covariance ma...

reason-behind-url-length-limits.hashnode.devMay 23, 2025 · 5 min read

Understanding the Reason Behind URL Length Limits

In web backend development, the idea of limiting URL length is often treated as an arbitrary constraint. However, this limit is deeply rooted in how HTTP requests are structured, how servers process them, and how to protect systems against certain ty...

hanweiwei

About

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hanweiwei's blogs

Enhancing Bean Validation Messages with Spring AOP: Injecting the Original Value

Java Lambda 表达式

Java 泛型中的协变与设计原则冲突

Analysis of Covariance in Java Generics and Conflicts with Design Principles

Understanding the Reason Behind URL Length Limits

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hanweiwei

About

Available for

hanweiwei's blogs

Enhancing Bean Validation Messages with Spring AOP: Injecting the Original Value

Java Lambda 表达式

Java 泛型中的协变与设计原则冲突

Analysis of Covariance in Java Generics and Conflicts with Design Principles

Understanding the Reason Behind URL Length Limits