title: Where do consumers for custom built annotations go in my source code?
body: <p>I noticed on some tutorials online that code for custom annotations made with the @interface keyword usually does not have any logic. After looking around I found that consumers query the item with that annotation. Here is the link I was looking at:
  <a href="http://www.objectpartners.com/2010/08/06/how-do-annotations-work/" rel="nofollow">http://www.objectpartners.com/2010/08/06/how-do-annotations-work/</a></p>
  
  <p>There is code here to find annotations and act based on what is found. My question is if I made an annotation that prevents using the letter a in the field where would my consumer go? My annotation @interface would just be empty. Where does the consumer go to have this done on compile time, for example?</p>
  
  <p>My understanding of annotations is obviously limited, so hopefully I am asking a clear question.</p>
  
  <p>Thanks!</p>