Create custom annotation in Java and use it when a method is called

Question

What I want to do is to create a custom annotation to use it on a Service, and each time a method is called from there first execute something. For example:

@CustomAnnotation
public Class MyService{

   public void myMethod(){
      //do something
   }
}

And when myMethod is called, do something before its code is executed, and then do what it has to do. Is there any way to do that? I need to do it with annotations, using interfaces or inheritance for that is useless because is for each method, not just one.

I know how to scan a package to get the classes annotated, but I don't know how to check it at runtime when the app is running.

Thank you!

Answer 1

It seems that what you need may be achieved by using AOP (aspect oriented programming).

Ive posted the code example here . It executes some code before the annotated methods and doesn't execute for others.

AOP allows you to do that without intervention in code of method-containing classes, you may alter methods behavior without altering methods themselves and their invocation code. You may even skip method execution using this technique (using @Around advice). It is useful if you need security checks before allowing method execution, for example.