title: Required message in SelectManyCheckbox componente
body: <p>I'm using JSF 2.1 with RichFaces 4 and I have a form with a <code>selectManyCheckbox</code> which I want it to have at least one item selected before processing the form.</p>
  
  <p>I put to true the attribute <code>required</code> but no message appears when I click the submit button without selecting at least one checkbox.</p>
  
  <p>How can I do that?</p>
  
  <p>Cheers</p>
  
  <p><strong>UPDATE</strong></p>
  
  <pre><code>                &lt;a4j:outputPanel id="cargaDependencias"&gt;
                      &lt;h:selectManyCheckbox layout="pageDirection" required="true" 
                                            requiredMessage="Seleccione al menos una dependencia"
                                            disabled="#{administrationBean.loadAllDependencies}"
                                            value="#{administrationBean.selectedDependencies}"&gt;
                          &lt;f:selectItems value="#{administrationBean.loadSelectDependencies}"/&gt;
                      &lt;/h:selectManyCheckbox&gt;
                  &lt;/a4j:outputPanel&gt;
                  &lt;br/&gt;&lt;br/&gt;
  
                  &lt;a4j:commandButton value="Actualizar Cubo"
                                     action="#{administrationBean.doUpdateInformationCube}"/&gt;
  </code></pre>