code: public String encodePartialActionURL(String url) {
          if (defaultExternalContext != null) {
              return defaultExternalContext.encodePartialActionURL(url);
          }
          throw new UnsupportedOperationException();
      }
docs: <p class="changed_added_2_0"><span class="changed_modified_2_2">Return</span>
  the input URL, after performing
  any rewriting needed to ensure that it can be used in a partial page
  submission (ajax request) to correctly identify an addressable action
  in the current application.</p>
  
  <p class="changed_added_2_2">See {@link #encodeActionURL(java.lang.String)}
  for the required specification of how to encode the {@link javax.faces.lifecycle.ClientWindow}.
  </p>
  
  <div class="changed_added_2_0">
  
  <p><p>
  
  <p><em>Servlet:</em>Returns the same encoded URL as the
  {@link #encodeActionURL(String url)} method.</p>
  
  <p><em>Portlet:</em>Returns an encoded URL that, upon HTTP POST, will
  invoke the RESOURCE_PHASE of the portlet lifecycle.</p>
  
  </div>
  
  @param url The input URL to be encoded
  
  @throws NullPointerException if <code>url</code>
  is <code>null</code>
  
  @since 2.0