Before configuring messages, ensure that the exception collector servlet has been activated in the application by inserting it in the servlet pipeline and adding the following lines to the web.xml file:

<context-param>
  <param-name>exception-collecting-enabled</param-name>
  <param-value>true</param-value>
</context-param>

The exception collector servlet creates messages from DropletException and ServletException objects that occur in the request.