Eitan Suez's Blog

February 2006 Archives

Proposed Annotations Enhancements

I think these should make for a nice extension to the existing Java 5 Annotation API:

1. From an Annotation, one should be able to navigate back to the programming element that it annotates.

   For example, a method annotation clearly marked with a Target of ElementType.METHOD cannot say getAnnotatedElement().getName(),

   There are two problems here. The first is the lack of the getAnnotatedElement() method The second is the fact that an AnnotatedElement is too primitive of an interface. You cannot actually invoke getName() on an annotated element. I feel that there should exist a basic ProgrammingElement implemented by or extended by all annotated elements.

2. The default value for an annotated element should not be restricted to a constant expression. Instead, the value should be a code block.

   For example, let's assume that I want to annotate methods to give them a caption. By default, the caption should be some kind of derivation from the method name it is bound to.

   That is,

   class MyClass
   {
     @MyMethodAt(caption="The X Method")
     public void method x()
     {
       // ..
     }
   }
   
   
   and
   
   
   @Retention(RetentionPolicy.RUNTIME)
   @Target(ElementType.METHOD)
   public @interface MyMethodAt
   {
     public String caption() 
        default
        {
          return getAnnotatedElement().name();  // see [1]
        }
   }
   

   As far as I know, this is currently not possible.

This work is licensed under a Creative Commons License.