title: WARN: Parameter didn't match accepted pattern in Struts 2
body: <p>I'm using Struts2.3.28. When I submit a form which uses the <a href="https://struts.apache.org/tag-developers/submit-tag.html" rel="nofollow noreferrer"><code>submit</code> tag</a> with the <code>method</code> attribute, I'm getting this warning:</p>
  <pre><code>WARN  com.opensymphony.xwork2.interceptor.ParametersInterceptor 
       warn- Parameter [method:save] didn't match accepted 
       pattern [[\w+((\.\w+)|(\[\d+\])|(\(\d+\))|
       (\['(\w|[\u4e00-\u9fa5])+'\])|(\('(\w|[\u4e00-\u9fa5])+'\)))*]]!
  </code></pre>
  <p>I have <code>struts.enable.DynamicMethodInvocation</code> set to <code>true</code>.</p>
  <p>I think this <code>acceptParamNames</code> property for the <a href="https://struts.apache.org/core-developers/parameters-interceptor.html" rel="nofollow noreferrer">Parameters Interceptor</a> (sort of a whitelist, it seems) was added in some recent version... The docs only says (basically)</p>
  <blockquote>
  <p>&quot;don't touch this&quot;
  .</p>
  </blockquote>
  <p>Great! So, what am I supposed to do if I still want to use the <code>method</code> attribute of <code>submit</code> tag?</p>
  <p><strong>Further:</strong> it's not clear for me the implications of this warning. If the pattern does not match neither the whitelist <code>acceptParamNames</code> nor the blacklist <code>excludeParams</code> (ah, the consistency), what is supposed to happen?</p>