Disable "Request processed successfully" Message

1. Add this in portlet.xml

<init-param>
    <name>add-process-action-success-action < /name>
    <value>false
< /init-param>

2. If you want to change for a particular action rather than for all actions.

public void addBook(ActionRequest actionRequest,
                                  ActionResponse actionResponse)
                                throws IOException, PortletException {

   ...............
   .................

    String successMsg = "Book added Successfully!";

    SessionMessages.add(actionRequest, "request_processed", successMsg);
}