logcheck.java

jsp超市管理系统系统,是用经典的MVC设计模式开发的非常适合初学者学习。

package com.myservlet;

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class LogCheck extends HttpServlet implements Filter{

	/**
	 * @author skyec.LiPeng
	 * 过滤器，过滤未登陆用户
	 */
	private static final long serialVersionUID = -4371549093291827375L;

	
	public void init(FilterConfig filterConfig) throws ServletException{ }
	
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException 
	{	
  
		//PrintWriter out = response.getWriter();
		response.setContentType("text/html;charset=gbk");
		
		HttpServletRequest req = (HttpServletRequest) request;
		HttpServletResponse res = (HttpServletResponse) response;
		HttpSession session = req.getSession(true);


		//从session里取得用户名信息，为了检查session里有无用户信息
		String logid = (String)session.getAttribute("logid");
		
		
		//如果session里没有得到用户信息,就跳转到登陆页面
		if (logid == null || "".equals(logid)){		
			
			res.sendRedirect("../login/login.jsp");		
			//out.print("未登陆。");
		}
		
		
		//否则，已经登陆,继续此次请求
		else{	
			
			chain.doFilter(request,response);		
		}
		
	}
	
	public void destroy(){ }


}