code: public void setResponseHeader(String name, String value) {
  
          if (defaultExternalContext != null) {
              defaultExternalContext.setResponseHeader(name, value);
          } else {
              throw new UnsupportedOperationException();
          }
  
      }
docs: <p class="changed_added_2_0">Set the response header with the given name and value.</p>
  
  <p><em>Servlet:</em>This must be performed by calling the
  <code>javax.servlet.http.HttpServletResponse</code> <code>setHeader</code>
  method.</p>
  
  <p>The default implementation throws
  <code>UnsupportedOperationException</code> and is provided for
  the sole purpose of not breaking existing applications that
  extend this class.</p>
  
  @param name The name of the response header.
  @param value The value of the response header.
  
  @since 2.0