Package com.google.auto.common

Class BasicAnnotationProcessor

  • All Implemented Interfaces:
    javax.annotation.processing.Processor
    public abstract class BasicAnnotationProcessor
extends javax.annotation.processing.AbstractProcessor
    An abstract Processor implementation that defers processing of Elements to later rounds if they cannot be processed.

    Subclasses put their processing logic in BasicAnnotationProcessor.Step implementations. The steps are passed to the processor by returning them in the steps() method, and can access the ProcessingEnvironment using AbstractProcessor.processingEnv.

    Any logic that needs to happen once per round can be specified by overriding postRound(RoundEnvironment).

    Ill-formed elements are deferred

    Any annotated element whose nearest enclosing type is not well-formed is deferred, and not passed to any Step. This helps processors to avoid many common pitfalls, such as ErrorType instances, ClassCastExceptions and badly coerced types.

    A non-package element is considered well-formed if its type, type parameters, parameters, default values, supertypes, annotations, and enclosed elements are. Package elements are treated similarly, except that their enclosed elements are not validated. See SuperficialValidation.validateElement(Element) for details.

    The primary disadvantage to this validation is that any element that forms a circular dependency with a type generated by another BasicAnnotationProcessor will never compile because the element will never be fully complete. All such compilations will fail with an error message on the offending type that describes the issue.

    Each Step can defer elements

    Each Step can defer elements by including them in the set returned by BasicAnnotationProcessor.Step.process(ImmutableSetMultimap); elements deferred by a step will be passed back to that step in a later round of processing.

    This feature is useful when one processor may depend on code generated by another, independent processor, in a way that isn't caught by the well-formedness check described above. For example, if an element A cannot be processed because processing it depends on the existence of some class B, then A should be deferred until a later round of processing, when B will have been generated by another processor.

    If A directly references B, then the well-formedness check will correctly defer processing of A until B has been generated.

    However, if A references B only indirectly (for example, from within a method body), then the well-formedness check will not defer processing A, but a processing step can reject A.

    • Constructor Detail

      • BasicAnnotationProcessor

        public BasicAnnotationProcessor()

    • Method Detail

      • init

        public final void init​(javax.annotation.processing.ProcessingEnvironment processingEnv)
        Specified by:
        init in interface javax.annotation.processing.Processor
        Overrides:
        init in class javax.annotation.processing.AbstractProcessor

      • postProcess

        @Deprecated
protected void postProcess()
        Deprecated.
        use postRound(RoundEnvironment) instead
        An optional hook for logic to be executed at the end of each round.

      • postRound

        protected void postRound​(javax.annotation.processing.RoundEnvironment roundEnv)
        An optional hook for logic to be executed at the end of each round.

      • getSupportedAnnotationTypes

        public final com.google.common.collect.ImmutableSet<java.lang.String> getSupportedAnnotationTypes()
        Returns the set of supported annotation types as collected from registered processing steps.
        Specified by:
        getSupportedAnnotationTypes in interface javax.annotation.processing.Processor
        Overrides:
        getSupportedAnnotationTypes in class javax.annotation.processing.AbstractProcessor

      • process

        public final boolean process​(java.util.Set<? extends javax.lang.model.element.TypeElement> annotations,
                             javax.annotation.processing.RoundEnvironment roundEnv)
        Specified by:
        process in interface javax.annotation.processing.Processor
        Specified by:
        process in class javax.annotation.processing.AbstractProcessor