public abstract class BasicAnnotationProcessor extends AbstractProcessor
Processor
implementation that defers processing of Element
s to later
rounds if they cannot be processed.
Subclasses put their processing logic in BasicAnnotationProcessor.ProcessingStep
implementations. The
steps are passed to the processor by returning them in the initSteps()
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)
.
ProcessingStep
. This helps processors to avoid many common pitfalls, such as
ErrorType
instances, ClassCastException
s 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.
ProcessingStep
can defer elementsEach ProcessingStep
can defer elements by including them in the set returned by
BasicAnnotationProcessor.ProcessingStep.process(SetMultimap)
; 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
.
Modifier and Type | Class and Description |
---|---|
static interface |
BasicAnnotationProcessor.ProcessingStep
The unit of processing logic that runs under the guarantee that all elements are complete and
well-formed.
|
processingEnv
Constructor and Description |
---|
BasicAnnotationProcessor() |
Modifier and Type | Method and Description |
---|---|
com.google.common.collect.ImmutableSet<String> |
getSupportedAnnotationTypes()
Returns the set of supported annotation types as a collected from registered
processing steps.
|
void |
init(ProcessingEnvironment processingEnv) |
protected abstract Iterable<? extends BasicAnnotationProcessor.ProcessingStep> |
initSteps()
Creates processing steps for this processor.
|
protected void |
postProcess()
Deprecated.
use
postRound(RoundEnvironment) instead |
protected void |
postRound(RoundEnvironment roundEnv)
An optional hook for logic to be executed at the end of each round.
|
boolean |
process(Set<? extends TypeElement> annotations,
RoundEnvironment roundEnv) |
getCompletions, getSupportedOptions, getSupportedSourceVersion, isInitialized
public final void init(ProcessingEnvironment processingEnv)
init
in interface Processor
init
in class AbstractProcessor
protected abstract Iterable<? extends BasicAnnotationProcessor.ProcessingStep> initSteps()
AbstractProcessor.processingEnv
is guaranteed to be set when this method is invoked.@Deprecated protected void postProcess()
postRound(RoundEnvironment)
insteadprotected void postRound(RoundEnvironment roundEnv)
public final com.google.common.collect.ImmutableSet<String> getSupportedAnnotationTypes()
getSupportedAnnotationTypes
in interface Processor
getSupportedAnnotationTypes
in class AbstractProcessor
public final boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv)
process
in interface Processor
process
in class AbstractProcessor
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