title: Spring Boot REST @RequestParam not being Validated
body: <p>I have tried a number of examples from the net and cannot get Spring to validate my query string parameter. It doesn't seem execute the REGEX / fail.</p>
  
  <pre><code>package my.controller;
  
  import org.springframework.beans.factory.annotation.Autowired;
  import org.springframework.web.bind.annotation.PathVariable;
  import org.springframework.web.bind.annotation.RequestMapping;
  import org.springframework.web.bind.annotation.RequestParam;
  import org.springframework.web.bind.annotation.RestController;
  
  import javax.validation.Valid;
  import javax.validation.constraints.Pattern;
  
  import static org.springframework.web.bind.annotation.RequestMethod.GET;
  
  @RestController
  public class MyController {
  
      private static final String VALIDATION_REGEX = "^[0-9]+(,[0-9]+)*$";
  
      @RequestMapping(value = "/my/{id}", method = GET)
      public myResonseObject getMyParams(@PathVariable("id") String id,
                                         @Valid @Pattern(regexp = VALIDATION_REGEX) 
                                         @RequestParam(value = "myparam", required = true) String myParam) {
           // Do Stuff!
      }
  
  }
  </code></pre>
  
  <p><strong>Current behaviour</strong></p>
  
  <pre><code>PASS - /my/1?myparam=1
  PASS - /my/1?myparam=1,2,3
  PASS - /my/1?myparam=
  PASS - /my/1?myparam=1,bob
  </code></pre>
  
  <p><strong>Desired behaviour</strong></p>
  
  <pre><code>PASS - /my/1?myparam=1
  PASS - /my/1?myparam=1,2,3
  FAIL - /my/1?myparam=
  FAIL - /my/1?myparam=1,bob
  </code></pre>
  
  <p>Thanks</p>