Java注释处理器，处理顺序

Question

I'm wondering if there is a way to process annotations from top down in a class, or at least in some deterministic order.

It doesn't seem like this is the case because the Processor class only provides:

boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv);

Where the RoundEnvironment allows you to access a Set of annotated elements, eg:

Set<? extends Element>  getElementsAnnotatedWith(TypeElement a)

Everything is in terms of unordered collections, and this makes the order of processing unpredictable. Is there anyway around this, besides trying to sort manually by element name or something?

Answer 1

As you have discovered, there is not a way to force processing of annotations in a specified order, using the current interfaces.

Here is a workaround. Suppose that you wish to process every declaration annotation, such as annotations on fields and methods. Don't register any callback for those declarations. Instead, invoke the annotation processor for every class. The annotation processor obtains the AST from javac, then walks it in the order you prefer. As an example, the Checker Framework uses this implementation strategy.

This workaround might not be sufficient for your needs, because it still processes each class in an arbitrary order -- for instance, one that depends on javac's staged compilation model.