title: Bean Validation for exact string match
body: <ol>
  <li>I want to validate a string for exact match in bean validation. Should I use <code>@Pattern</code> or is there a different method to do so?</li>
  <li>If <code>@Pattern</code> is the way to go, what is the <code>regex</code>?</li>
  <li>Can I use two  <code>@Pattern</code> annotation for two different groups on a same field?</li>
  </ol>