Find Method Arguments of annotated Method using Java Annotation Processor?

Question

I have the following annotation:

@Target(ElementType.METHOD)
public @interface MyAnn {
}

and a method annotated with @MyAnn:

  @MyAnn
  Object myMehtod(Object x) {
  ...
  }

Using a Java annotation processor I get the annotated element as:

Element annotatedElement // = myMehtod

How do I get the return type of this method?
How do I get the arguments of this method?
How do I get the name of the arguments of this method?

Simon Warta · Accepted Answer · 2015-10-11 12:21:05Z

8

Here is my solution:

ExecutableType executableType = (ExecutableType)annotatedElement.asType();
List<? extends TypeMirror> parameters = executableType.getParameterTypes();
TypeMirror param1 = parameters.get(0);
DeclaredType declaredType = (DeclaredType)param1;
List<? extends AnnotationMirror> anns = ((TypeElement)declaredType.asElement()).getAnnotationMirrors( );

edited Oct 11, 2015 at 12:21

Simon Warta

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answered Jul 7, 2015 at 9:28

Sven Bauer

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3 Comments

Samuel Over a year ago

ExecutableType executableType = (ExecutableType)annotatedElement.asType(); is causing me compiler errors. Types are not compatible.

Mooing Duck Over a year ago

@Samuel That means the thing with the annotation is not a method. Perhaps you've accidentally annotated the return type instead? That would explain the problems you encountered.

Asad-ullah Khan Over a year ago

you are supposed to cast the element, not the type: (ExecutableElement)annotatedElement

Ahmad Bawaneh · Accepted Answer · 2019-01-18 17:47:37Z

5

ExecutableElement method = ...

You can get the return type of the method with

TypeMirror returnType = mehod.asType()

You can get the arguments of the method with

List<? extends VariableElement> parameters = method.getParameters();

You can get the name of the parameter with

parameters.forEach(p -> {
            String name = p.getSimpleName().toString();
            TypeMirror type = p.asType();
   });

answered Jan 18, 2019 at 17:47

Ahmad Bawaneh

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2 Comments

Clément Honoré Over a year ago

Hi, I always get "arg0" as name for my parameter. What am I missing ?

Andrei Kazarov Over a year ago

One has to add -parameters option to javac when compiling the classes to get parameters names added to metadata for reflection.

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