Finding annotated annotations

Question

There is an annotation @MarkerAnnotation. It can be added directly to method. or to any other annotation, like

@MarkerAnnotation
@Interface CustomAnnotation {...}

and this @CustomAnnotation can also be added directly to methods. That's the standard way many frameworks let users add their own annotation (e.g. spring).

Now, given a class, I want to find all methods marked directly or indirectly with @MarkerAnnotation. For every method I also want to find the associated @MarkerAnnotation and/or @CustomAnnotation. Is there any tool that I can use or I have to do it manually?

john16384 · Accepted Answer · 2017-08-11 12:16:59Z

2

Spring has an AnnotationUtils class in their core project that does what you want. The javadoc for findAnnotation:

Find a single Annotation of annotationType on the supplied Method, traversing its super methods (i.e., from superclasses and interfaces) if the annotation is not directly present on the given method itself. Correctly handles bridge Methods generated by the compiler.

Meta-annotations will be searched if the annotation is not directly present on the method.

Annotations on methods are not inherited by default, so we need to handle this explicitly.

answered Aug 11, 2017 at 12:16

john16384

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Robin Green · Accepted Answer · 2013-11-23 11:50:12Z

0

For a generic approach, you should use the annotation processor facility of javac, which requires you to write an annotation processor which uses the APIs in packages javax.annotation.processing, and javax.lang.model and its subpackages. This code will run inside javac. (There is an older tool, apt, which is separate from javac, but apt is deprecated in Java 7.)

In particular, when you visit each Element, you can call getAnnotationMirrors on it. Then, for each of those annotations, call getAnnotationType().asElement() to get the Element for the annotation type. You may need to use recursion to find the indirect annotations, if there is more than one level of indirection possible.

answered Nov 23, 2013 at 11:50

Robin Green

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Comments

subash · Accepted Answer · 2013-11-23 12:02:47Z

for example like this...

public class Test{
         @MarkerAnnotation
         public void TestMethod1(){

         }

         @CustomAnnotation
         @MarkerAnnotation
         public void TestMethod2(){

         }

    }

you can parse like this..

public class AnnotationTest{

         public static void main(String[] args){
              Method[] methods = Test.class.getDeclaredMethods();
              for(Method method: methods){
                   Annotation[] annotations = method.getAnnotations();
               for(Annotation annotation: annotations){
                   if(annotation instanceof MarkerAnnotation)
                           System.out.println(method.getName() +" annotated with MarkerAnnotation");
                      if(annotation instanceof CustomAnnotation)
                           System.out.println(method.getName() +" annotated with CustomAnnotation");
                   }
              }
         }
    }

and if you want check CustomAnnotation have MarkerAnnotation, then do like this..

    if(CustomAnnotation.class.isAnnotation()){
        Annotation[] annotations = CustomAnnotation.class.getAnnotations();
        if(annotations[0] instanceof MarkerAnnotation){
            System.out.println("CustomAnnotation have MarkerAnnotation");
        }
    }

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