title: Exception handling in primefaces not working
body: <p>I am facing  an issue with p:ajaxExceptionHandler.  The p:ajaxExceptionHandler code does not seem to get invoked at all.. I have the configuration in web.xml as per primefaces documentation. Basically When an exception occurs, I want to show a pop up on the same page that is not happening</p>
  
  <p>In the console I see the error, </p>
  
  <pre><code>&lt;Jul 27, 2015 2:33:22 PM EDT&gt; &lt;Error&gt; &lt;javax.faces.event&gt; &lt;BEA-000000&gt; &lt;Received
   'java.lang.NullPointerException' when invoking action listener '#{BeanName.methodName()}' for component 'delete'&gt;
  &lt;Jul 27, 2015 2:33:22 PM EDT&gt; &lt;Error&gt; &lt;javax.faces.event&gt; &lt;BEA-000000&gt; &lt;java.lan
  g.NullPointerException: Exception
  </code></pre>
  
  <p>I dont want to be redirected to a different page, but just tried adding an entry in web.xml to check if that works but still I get the same error. </p>
  
  <p>My requirement is to show a pop dialog conditionally. In the backing bean I have a checkPopup method which will throw an exception if some condition is not met which is when I want to show the pop up. Please help me if I am missing something. Thanks!</p>
  
  <h2>MyCode</h2>
  
  <pre><code>&lt;p:commandButton id="delete" value="Save and Proceed" styleClass="deleteBtn" type="submit"  icon="ui-icon-disk" actionListener="#{BeanName.checkPopUp()}"
                              update=":cbForm:topPanel check" ajax="true" &gt;
              &lt;/p:commandButton&gt;
              &lt;p:ajaxExceptionHandler type="java.lang.NullPointerException" update="check" onexception="PF('confirmDlg').show()" /&gt; 
                      &lt;p:confirmDialog rendered="#{BeanName.methodName()}" id="check" header="confirmation" widgetVar="confirmDlg" global="true"  severity="info" closable="false"&gt;
                          &lt;f:facet name="message"&gt;
                          &lt;h:outputText value="#BeanName.BeanName.dialogMsg}"/&gt;
                          &lt;/f:facet&gt;
                          &lt;p:commandButton value="#{resbndl.btnOK}" type="submit" process="@this" action="#{BeanName.methodName()}" styleClass="ui-confirmdialog-yes" icon="ui-icon-check" onstart="PF('confirmDlg').hide()" update=":cForm:tView:check"/&gt;
                          &lt;p:commandButton value="#{resbndl.btnCancel}" type="submit" process="@this" action="#{BeanName.methodName()}" update=":cForm:tView:fieldName"  styleClass="ui-confirmdialog-no" icon="ui-icon-close" /&gt;
                      &lt;/p:confirmDialog&gt;  
  </code></pre>
  
  <p>checkPopUp code</p>
  
  <pre><code>public String checkPopUp (){
          if (value == null)
              throw new java.lang.NullPointerException("Exception");
          return validate(2);
      }
  </code></pre>