로그 인 여 부 를 판단 하 는 차단기 CheckLoginFilter

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.util.List;
import java.util.ArrayList;
import java.util.StringTokenizer;
import java.io.IOException;

/**    
 *               ，     ，                
 *         
 * checkSessionKey       Session             
 * redirectURL        ，          ，URL    ContextPath     
 * notCheckURLList      URL  ，     ，   URL      ContextPath    
 */
public class CheckLoginFilter implements Filter {
	protected FilterConfig filterConfig = null;

	private String redirectURL = null;

	private List notCheckURLList = new ArrayList();

	private String sessionKey = null;

	public void doFilter(ServletRequest servletRequest,
			ServletResponse servletResponse, FilterChain filterChain)
			throws IOException, ServletException {
		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 destroy() {
		notCheckURLList.clear();
	}

	private boolean checkRequestURIIntNotFilterList(HttpServletRequest request) {
		String uri = request.getServletPath()
				+ (request.getPathInfo() == null ? "" : request.getPathInfo());
		return notCheckURLList.contains(uri);
	}

	public void init(FilterConfig filterConfig) throws ServletException {
		this.filterConfig = filterConfig;
		redirectURL = filterConfig.getInitParameter("redirectURL");
		sessionKey = filterConfig.getInitParameter("checkSessionKey");

		String notCheckURLListStr = filterConfig
				.getInitParameter("notCheckURLList");

		if (notCheckURLListStr != null) {
			StringTokenizer st = new StringTokenizer(notCheckURLListStr, ";");
			notCheckURLList.clear();
			while (st.hasMoreTokens()) {
				notCheckURLList.add(st.nextToken());
			}
		}
	}
}