コアJ2EEパターン - Front Controllerパターン

public class SampleController extends HttpServlet {
  protected void processRequest(HttpServletRequest
    request, HttpServletResponse response)
    throws ServletException, java.io.IOException {

    String page = null;
    try {
      //process authority
      processAuthority(request, response);
      //manage session
      processSession(request, response);

      // Use a helper object to gather parameter
      // specific information.
      RequestHelper helper = new
         RequestHelper(request);

      Command cmdHelper= helper.getCommand();

      // Command helper perform custom operation
      page = cmdHelper.execute(request, response);

    }
    catch (Exception e) {
      LogManager.logMessage("Error Message HERE");
      page = resource.getErrorPage(e);
    }
    // dispatch control to view
    dispatch(request, response, page);
  }

  protected void doGet(HttpServletRequest request,
    HttpServletResponse response)
    throws ServletException, java.io.IOException {
      processRequest(request, response);
  }

  protected void doPost(HttpServletRequest request,
    HttpServletResponse response)
    throws ServletException, java.io.IOException {
        processRequest(request, response);
  }

  protected boolean processAuthority(HttpServletRequest request,
    HttpServletResponse response) {
      ... //authority control code here
  }

  protected void processSession(HttpServletRequest request,
    HttpServletResponse response) {
      ... //session management code here
  }

  protected void dispatch(HttpServletRequest request,
    HttpServletResponse response,
    String page)
  throws  javax.servlet.ServletException,
    java.io.IOException {
    RequestDispatcher dispatcher =
      getServletContext().getRequestDispatcher(page);
    dispatcher.forward(request, response);
  }
}