title: How to check if Request object contains a given parameter
body: <p>I have a REST endpoint /v1/abc.
  It is a POST method.
  In the request body i send an object Test which looks as below.</p>
  
  <pre><code>Class Test {
     Boolean flag = null;
     String name = null;
  }
  </code></pre>
  
  <p>I invoke the endpoint using swagger.</p>
  
  <p>In the request body, i set below.</p>
  
  <pre><code>{
   "name" : "hello"
  }
  </code></pre>
  
  <p>If you notice, I am not sending flag at all.
  In my API, i want to test if the request object has flag or not. If not present, i throw an exception.</p>
  
  <p>Can you tell me how to achieve this?</p>