title: How to submit null value of p:selectOneMenu?
body: <p>I have file <code>submission.xhtml</code> with code snippet:</p>
  
  <pre><code>&lt;p:outputLabel for="cbFilterPlanYear" value="Choose time period"/&gt;
  
  &lt;p:outputPanel&gt;
      &lt;p:selectOneMenu id="cbFilterPlanMonth" value="#{SubmissionController.miFilterMonth}" style="width: 50%"&gt;
          &lt;f:selectItem itemLabel="#{null}" itemValue="#{null}" /&gt;
          &lt;f:selectItems value="#{SubmissionController.mlistMonth}" var="month" itemValue="#{month}" itemLabel="#{month}" /&gt;
          &lt;p:ajax event="change" update="@this" /&gt;
      &lt;/p:selectOneMenu&gt;
  
      &lt;p:selectOneMenu id="cbFilterPlanYear" value="#{SubmissionController.miFilterYear}" style="width: 50%"&gt;
          &lt;f:selectItem itemLabel="#{null}" itemValue="#{null}" /&gt;
          &lt;f:selectItems value="#{SubmissionController.mlistYear}" var="year" itemValue="#{year}" itemLabel="#{year}" /&gt;
          &lt;p:ajax event="change" update="@this" /&gt;
      &lt;/p:selectOneMenu&gt;
  &lt;/p:outputPanel&gt;
  </code></pre>
  
  <p>These line of code for search criteria(s), for filter data. <strong>I can't submit NULL value</strong> (As you know, it also don't set specific criteria to search query). Help me submit null value from <code>p:selectOneMenu</code>.</p>
  
  <p><a href="https://i.stack.imgur.com/44Ysb.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/44Ysb.png" alt="enter image description here"></a></p>