title: Validation nested models in spring boot
body: <p>I have a problem with validation of nested models, look:   </p>
  
  <pre><code>class A{
     @NotNull
     Integer i;
     B b;
  }
  class B{
     @NotNull
     Integer j;
  }
  </code></pre>
  
  <p>In spring controller:<br>
  <code>@Valid @RequestBody...</code></p>
  
  <p>It properly validate <code>i</code>, but not validate <code>j</code>.   How to force Spring to validate arbitraly deep ?   </p>
  
  <p>And second thing:<br>
  Is it possible to do following validation:   Object of class 'A' is proper only and only if exactly one of <code>i</code> an <code>j</code> is <code>null</code>.   </p>
  
  <pre><code>class A{
     Integer i;
     Integer j;
  }
  </code></pre>