title: WARNING: Form token does not match the session token null
body: <p>What is the reason for this warning?</p>
  
  <pre><code>WARNING: Form token PR78LAIFZJQRTL66GGAJDT61511L6YHN does not match the session token null
  </code></pre>
  
  <p><strong>JSP:</strong></p>
  
  <pre><code>&lt;s:form method="post" action="test"&gt;
       &lt;s:token&gt;&lt;/s:token&gt;
       Email:&lt;input name="email" /&gt;
  &lt;/s:form&gt;
  </code></pre>
  
  <p><strong>Struts.xml:</strong></p>
  
  <pre><code>&lt;action name="test" class="test.RegisterAction"&gt;
      &lt;interceptor-ref name="defaultStack" /&gt;
      &lt;interceptor-ref name="token" /&gt; 
      &lt;result name="invalid.token"&gt;/error.jsp&lt;/result&gt; 
      &lt;result&gt;/user/success.jsp&lt;/result&gt;
      &lt;result name="error"&gt;/error.jsp&lt;/result&gt;
  &lt;/action&gt;
  </code></pre>