title: Java 8 Optional<?> validation unwrapper in Spring
body: <p>In my Spring Boot project when using the following validation rules in my DTO</p>
  
  <pre><code>@Length(max = 70)
  @UnwrapValidatedValue
  private Optional&lt;String&gt; vendorName;
  </code></pre>
  
  <p>I am getting the following exception</p>
  
  <pre><code>javax.validation.ValidationException: HV000182: No validation value unwrapper is registered for type java.util.Optional&lt;java.lang.String&gt;
  </code></pre>
  
  <p>I can't just find anywhere how to register custom validation value unwrapper in Spring</p>