backfilter.java~3~

JBuilder 2006 +SQL Server2000 +JavaBean+JSP开发的宠物医院管理系统

package com.pet.util;

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

public class BackFilter extends HttpServlet implements Filter {
    private FilterConfig filterConfig;
    //Handle the passed-in FilterConfig
    public void init(FilterConfig filterConfig) throws ServletException {
        this.filterConfig = filterConfig;
    }

    //Process the request/response pair
    public void doFilter(ServletRequest request, ServletResponse response,
                         FilterChain filterChain) {
        HttpServletResponse sp = (HttpServletResponse) response;
       PrintWriter out = null;
       try {
           out = sp.getWriter();
       } catch (IOException ex) {
       }
       HttpServletRequest re = (HttpServletRequest) request;
       HttpSession session = re.getSession();
       try {
           if (session.getAttribute("name") != null) {
               out.println("<script type=\"text/javascript\" language=\"javascript\">alert(\"请输入用户名或密码！\");window.history.go(-1);</script>");
           }else{
               filterChain.doFilter(request, response);
           }

        } catch (ServletException sx) {
            filterConfig.getServletContext().log(sx.getMessage());
        } catch (IOException iox) {
            filterConfig.getServletContext().log(iox.getMessage());
        }
    }

    //Clean up resources
    public void destroy() {
    }
}