title: Spring form checkbox tag: why generate a hidden element?
body: <p>I am using Spring MVC for a web application. On a form, I have</p>
  
  <pre><code>&lt;form:checkbox path="agreeTerms" id="agreeTerms"/&gt;
  </code></pre>
  
  <p>When the page is rendered, the following HTML is generated</p>
  
  <pre><code>&lt;input id="agreeTerms" type="checkbox" value="true" name="agreeTerms"&gt;
  &lt;input type="hidden" value="on" name="_agreeTerms"&gt;
  </code></pre>
  
  <p>Does anyone know the purpose of the hidden tag? What would happen if the hidden input tag is removed?</p>
  
  <p>Thanks!</p>