title: Where should I put @Transactional annotation: at an interface definition or at an implementing class?
body: <p>The question from the title in code:</p>
  
  <pre><code>@Transactional (readonly = true)
  public interface FooService {
     void doSmth ();
  }
  
  
  public class FooServiceImpl implements FooService {
     ...
  }
  </code></pre>
  
  <p>vs</p>
  
  <pre><code>public interface FooService {
     void doSmth ();
  }
  
  @Transactional (readonly = true)
  public class FooServiceImpl implements FooService {
     ...
  }
  </code></pre>