<filter>
        <filter-name>checkLogin</filter-name>
        <filter-class>hospital.filters.LoginFilter</filter-class>  
        <init-param>
            <param-name>redirectURL</param-name>
            <param-value>/web/login.jsp</param-value>
        </init-param>
        <init-param>
            <param-name>checkSessionKey</param-name>
            <param-value>loginName</param-value>
        </init-param>

        <init-param>
            <param-name>notCheckURLList</param-name>
            <param-value>/web/LoginServlet;/web/login.jsp</param-value>
        </init-param>
    </filter>
     
    <filter-mapping>
        <filter-name>checkLogin</filter-name>
        <url-pattern>/web/*</url-pattern>
    </filter-mapping>

package hospital.filters;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class LoginFilter implements Filter{

    protected FilterConfig filterConfig = null;
    private String redirectURL = null;
    private List notCheckURLList = new ArrayList();
    private String sessionKey = null;
    
    public void destroy() {
        System.out.println("destroy");
        notCheckURLList.clear();
        
    }

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) 
        throws IOException, ServletException {
        System.out.println("doFilter");
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;
        HttpSession session = request.getSession();
        if (sessionKey == null) {
            filterChain.doFilter(request, response);
            return;
        }
        if ((!checkRequestURIIntNotFilterList(request))
                && session.getAttribute(sessionKey) == null) {
            response.sendRedirect(request.getContextPath() + redirectURL);
            return;
        }
        filterChain.doFilter(servletRequest, servletResponse);
        
    }

    public void init(FilterConfig arg0) throws ServletException {
        System.out.println("init");
        this.filterConfig = filterConfig;
        redirectURL = filterConfig.getInitParameter("redirectURL");
        sessionKey = filterConfig.getInitParameter("checkSessionKey");
        String notCheckURLListStr = filterConfig
                .getInitParameter("notCheckURLList");
        if (notCheckURLListStr != null) {
            StringTokenizer st = new StringTokenizer(notCheckURLListStr, ";&quo