title: How to get <f:attribute> value inside <p:ajax listener> method?
body: <p>I have a checkbox component with a <code>&lt;f:attribute&gt;</code> and a <code>&lt;p:ajax listener&gt;</code>.</p>
  
  <pre><code>&lt;h:selectManyCheckbox ...&gt;
    &lt;p:ajax listener="#{locationHandler.setChangedSOI}" /&gt;
    &lt;f:attribute name="Dummy" value="test" /&gt;
    ...
  &lt;/h:selectManyCheckbox&gt;
  </code></pre>
  
  <p>I tried to get the <code>&lt;f:attribute&gt;</code> value of <code>test</code> inside the listener method as below:</p>
  
  <pre><code>public void setChangedSOI() throws Exception {
      FacesContext context = FacesContext.getCurrentInstance();
      Map&lt;String, String&gt; map = context.getExternalContext().getRequestParameterMap();
      String r1 = map.get("Dummy");
      System.out.println(r1);
  }
  </code></pre>
  
  <p>However, it printed <code>null</code>. How can I get it?</p>