Understanding Java Annotations and Annotation Processing

Annotations in Java are like magic markers. They started as just metadata (`@Override`), but with frameworks like Spring and Lombok, they have become powerful tools for code generation. I was curious how Lombok generates getters and setters at compile time without runtime reflection. It uses the Annotation Processing Tool (APT). I tried writing my own annotation processor to generate builder classes for my domain objects. It was tough, but it taught me a lot about the Java compiler internals. You have to work with the abstract syntax tree (AST). Annotations are a way to shift boilerplate code generation from the developer to the compiler. Just be careful not to overuse them. Too many custom annotations can make the code hard to understand for newcomers who don’t know the magic happening under the hood.