更改注释方法的返回类型

Question

given the following custom annotation

 @Retention(RetentionPolicy.RUNTIME)
 @Target(ElementType.FIELD)
 public @interface TGT {
  String age();
}

and somewhere in a class code it is used for a field as :

  @TGT(age="someValue")
  private String someID;

Is it possible to change the return value of someID's method age() from "someValue": to so something else or in other words other String value?So when someone gets someID's annotation via reflection and then invokes the age() method of the annotation to get different value?

Answer 1

Yes, it is possible but not with pure reflection. If you want to change the object without replacing it by another object you'll have to use a bytecode manipulation lib like ASM (see how it is done in Lombok ). But this way would be very complex.

In case if you are allowed to replace an abject by a proxy it would even be possible with pure reflection + aspects engine (se how Spring does it with help of CGLIB ).