Java 运行时相当于使用 javax Processor / google @AutoService 进行注释处理

Question

I have worked with annotation processing on RetentionPolicy.SOURCE level, using javax.annotation.processing.Processor/AbstractProcessor and com.google.auto.service.@AutoService before, that's when I first discovered the very helpful RoundEnvironment.getElementsAnnotatedWith() .

Now, in a completely unrelated project, I need the same functionality, but at runtime. In other words, I have the Annotation

@Target({ElementType.CONSTRUCTOR, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface Mapper {
    Class<?> forUID() default Object.class;
}

and I want to obtain every single element (of course it can only be constructors or methods) anntotated with @Mapper . Can I use RoundEnvironment at runtime? If yes, how do I obtain an instance of it? If no, is there a runtime equivalent to it? Thanks in advance.

Using:

• JDK 11 (openjdk11)
• Maven 3.6.3

Answer 1

Annotation processing is a compile time only tool, the retention on the annotation is just saying if the annotation will be available at runtime or just in source, for run time you can use reflection, but also you still can use annotation processor at compile time to generate a class that list all the types annotated with a specific annotation.