frontcontroller.java

一个简单的EJB实例.用DB2连接.JSP页面.很好用.供大家学习

package com.xyz.servlet;

import java.io.IOException;
import java.util.Enumeration;
import java.util.HashSet;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.xyz.command.CmdDisplayLocation;
import com.xyz.command.CmdError;
import com.xyz.command.CmdHome;
import com.xyz.command.CmdRecordPurchases1;
import com.xyz.command.CmdRecordPurchases2;
import com.xyz.command.ICommand;

/**
 * @version 	1.0
 * @author Lou Mauget
 */
public class FrontController extends HttpServlet implements ICommand {

	/**
	* @see com.xyz.command.ICommand#String (HttpServletRequest, HttpServletResponse)
	*/
	public String execute(
		HttpServletRequest request,
		HttpServletResponse response)
		throws ServletException, IOException {
		return "";
	}

	/**
	* @see javax.servlet.http.HttpServlet#void (javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
	*/
	public void doGet(HttpServletRequest req, HttpServletResponse resp)
		throws ServletException, IOException {

		doPost(req, resp);
	}

	/**
	 * @see javax.servlet.http.HttpServlet#void (javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
	 */
	public void doPost(HttpServletRequest req, HttpServletResponse resp)
		throws ServletException, IOException {

		Enumeration enum = req.getParameterNames();
		HashSet set = new HashSet();
		while (enum.hasMoreElements())
			set.add(enum.nextElement());

		ICommand cmd = mapCommand(set);
		String target = cmd.execute(req, resp);
		req.getRequestDispatcher(target).forward(req, resp);

	}

	/**
	 * Returns an ICommand object corresponding to the passed
	 * command string in the set. Returns an error 
	 * ICommand object if the string is null or unidentifiable
	 * @param set java.util.HashSet
	 */
	protected ICommand mapCommand(HashSet set) {

		ICommand result = null;

		if (set == null)
			result = new CmdError();
		else if (set.contains("CmdHome"))
			result = new CmdHome();
		else if (set.contains("CmdRecordPurchases1"))
			result = new CmdRecordPurchases1();
		else if (set.contains("CmdRecordPurchases2"))
			result = new CmdRecordPurchases2();
		else if (set.contains("CmdDisplayLocation"))
			result = new CmdDisplayLocation();
		else
			result = new CmdError();

		return result;
	}

}