mailcontrollerservlet.java

21天学通java的示例程序源代码

package ezmail;

import javax.servlet.*;
import javax.servlet.http.*;

import java.io.*;
import java.util.*;

import ezmail.Constants;

/**
 *  This servlet is the web front component for the ezmail web app.  It expects the following parameter(s):
 *
 *  <ul>
 *    <li>action - the name of the action to perform</li>
 *  </ul>
 */
public class MailControllerServlet extends HttpServlet {

	private HashMap actionTable;
	private HashMap pageTable;

	/**
	 *  The method performs the following operations:
	 *
	 *  <ol>
	 *    <li>  Create the WebAction implementations and place in HashMap
	 */
	public void init() throws ServletException {

		try {
			log("in the init() method");

			//  Create the Action implementations and place in HashMap
			actionTable = new HashMap();
			actionTable.put(Constants.LOGIN_KEY, new LoginAction());
			actionTable.put(Constants.SEND_MESSAGE_KEY, new SendMessageAction());
			actionTable.put(Constants.VIEW_MESSAGE_LIST_KEY, new ViewMessageListAction());
			actionTable.put(Constants.VIEW_MESSAGE_DETAIL_KEY, new ViewMessageDetailAction());
			actionTable.put(Constants.LOGOUT_KEY, new LogoutAction());

			//  Setup the destination pages
			pageTable = new HashMap();
			pageTable.put(Constants.LOGIN_KEY, Constants.HOME_PAGE);
			pageTable.put(Constants.SEND_MESSAGE_KEY, Constants.SEND_MESSAGE_PAGE);
			pageTable.put(Constants.VIEW_MESSAGE_LIST_KEY, Constants.VIEW_MESSAGE_LIST_PAGE);
			pageTable.put(Constants.VIEW_MESSAGE_DETAIL_KEY, Constants.VIEW_MESSAGE_DETAIL_PAGE);
			pageTable.put(Constants.LOGOUT_KEY, Constants.LOGOUT_PAGE);
		}
		catch (Exception exc) {
			exc.printStackTrace();
			throw new ServletException(exc.getMessage());
		}
	}


	protected void process(HttpServletRequest request, HttpServletResponse response)
		throws ServletException, IOException {

		try {
			// retrieve the desired Action implementation
			String actionParam = request.getParameter(Constants.ACTION_PARAM);
			Action tempAction = (Action) actionTable.get(actionParam);

			// now let's perform the action!
			// note:  getServletContext() is inherited from javax.servlet.GenericServlet
			tempAction.perform(getServletContext(), request, response);

			// Dispatch/forward the request to destination page
			String destPage = (String) pageTable.get(actionParam);

			System.out.println("destPage = " + destPage);

			ServletContext context = getServletContext();
			RequestDispatcher dispatcher = context.getRequestDispatcher(destPage);
			dispatcher.forward(request, response);
		}
		catch (ActionException exc) {
			exc.printStackTrace();
			throw new ServletException(exc.getMessage());
		}
	}


	/**
	 *  Forwards requests to the process(...) method
	 */
    public void doGet (HttpServletRequest request, HttpServletResponse response)
	  throws ServletException, IOException {

		process(request, response);
    }

	/**
	 *  Forwards requests to the process(...) method
	 */
	public void doPost(HttpServletRequest request, HttpServletResponse response)
		throws ServletException, IOException {

		process(request, response);
	}


}