ex6_16.txt

j2ee core design patterns

Example 6.16 Command and Controller Strategy 
/** This processRequest method is invoked from both 
* the servlet doGet and doPost methods **/
protected void processRequest(HttpServletRequest request,
    HttpServletResponse response) throws ServletException,
    java.io.IOException {

  String resultPage;
  try {
    RequestHelper helper = new RequestHelper(request);

    /** the getCommand() method internally uses a 
      * factory to retrieve command objects as follows:
      * Command command = CommandFactory.create(
      * request.getParameter(op));
     **/
    Command command =  helper.getCommand();
    // delegate request to a command object helper
    resultPage = command.execute(request, response);
  } catch (Exception e) {
    LogManager.logMessage("FrontController", e.getMessage());
    resultPage = ApplicationResources.getInstance().getErrorPage(e);
  }
  dispatch(request, response, resultPage);
}