title: Static nested class as parameter in REST service
body: <p>I see this in some code , and I have a hunch it is not a good practice. What are your opinions ?</p>
  
  <pre><code>@RestController
  public class AddController {
      @RequestMapping(value="/Add", method = RequestMethod.POST) 
      public ActionResponse add(@Valid @RequestBody    AddRequest request) {
          // Method does as much as necessary
      }
      static class AddCRequest {              
          public String parameter1;
          public long parameter2;
          public long parameter3;
      }
  }
  }
  </code></pre>
  
  <p>Having the static nested class as a parameter of of the methdos of the service , is it good ? Static implies only one instance of the class ? How will it behave with concurrency ?
  A very good theorical-technical explanation would be appreciated.</p>