ex6_70.txt

j2ee core design patterns

Example 6.70 	Controller Servlet with Command and Controller Strategy
public class Controller extends HttpServlet {
	/** Processes requests for both HTTP  
	 * <code>GET</code> and <code>POST</code> methods.
	 * @param request servlet request
	 * @param response servlet response
	 */
	protected void processRequest(HttpServletRequest request,
			HttpServletResponse response)
			throws ServletException, java.io.IOException {
		String next;

		try {
			// create Context Object
			RequestContext requestContext =
				new RequestContext(request, response);

			// invoke request-processing components to
			// handle incoming request
			ApplicationController applicationController = 
				new ApplicationControllerImpl();
			ResponseContext responseContext =
				applicationController.handleRequest(requestContext);

			// invoke response-processing components to
			// handle response logic          
			applicationController.handleResponse(requestContext,
				responseContext);
		}
		catch (Exception e) {
			LogManager.logMessage( 
				"FrontController(CommandStrategy)",
				e.getMessage() );

			/** ApplicationResources provides a simple API 
			  * for retrieving constants and other 
			  * preconfigured values **/
			next = ApplicationResources.getInstance().getErrorPage(e);
		}

		dispatch(request, response, next);

	}

	/** Handles the HTTP <code>GET</code> method.
	 * @param request servlet request
	 * @param response servlet response
	 */
	protected void doGet(HttpServletRequest request, 
			HttpServletResponse response)
			throws ServletException, java.io.IOException {
		processRequest(request, response);
	}

	/** Handles the HTTP <code>POST</code> method.
	 * @param request servlet request
	 * @param response servlet response
	 */
	protected void doPost(HttpServletRequest request, 
			HttpServletResponse response)
			throws ServletException, java.io.IOException {
		processRequest(request, response);
	}

	/** Returns a short description of the servlet. */
	public String getServletInfo() {
		return getSignature();
	}

	/** dispatcher method */
	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);
	}

	public void init(ServletConfig config) throws ServletException {
		super.init(config);
	}

	public void destroy() { }

	private String getSignature() {
		return "ServiceToWorker-Controller";
	}
}