Rust for Java Programmers | Rust 面向 Java 程序员

Macros Primer
宏入门

What you’ll learn: Why Rust macros exist, how they differ from Java annotations or code generation, and which macros matter first.
本章将学习： Rust 宏为什么存在、它和 Java 注解或代码生成有什么差别，以及最先应该认识哪些宏。

Difficulty: 🟡 Intermediate
难度： 🟡 中级

Macros in Rust are syntax-level generation tools. They are much closer to language extension points than to Java annotations.
Rust 宏是语法级生成工具，它更接近语言扩展点，而不是 Java 注解那一路。

First Macros to Recognize
最先要认熟的宏

• println!
• vec!
• format!
• dbg!
• #[derive(...)]

Why Java Developers Should Care
Java 开发者为什么要关心

In Java, many conveniences come from frameworks, annotation processors, Lombok-style generation, or reflection. Rust often solves the same ergonomics problem earlier in the compilation pipeline through macros.
Java 里很多便利性来自框架、注解处理器、Lombok 式代码生成或者反射。Rust 则经常在更前面的编译阶段通过宏把这件事解决掉。

Practical Advice
实用建议

• learn to read macro invocations before learning to write macros
  先学会读宏，再学写宏。
• treat derive macros as the normal entry point
  把 derive 宏当成最自然的入口。
• use cargo expand when a macro stops making sense
  一旦宏看不懂，就用 cargo expand。

Macros are powerful, but most day-to-day Rust work only needs comfort with using them, not authoring them.
宏确实很强，但绝大多数日常 Rust 开发只需要会用，不需要一上来就自己写。