过滤器权限校验

package com.web.study;

import java.io.IOException;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.Filter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class PermissionFilter implements Filter {

	public PermissionFilter() {

	}

	private FilterConfig filterConfig;

	public void init(FilterConfig filterConfig) throws ServletException {

	}

	public void doFilter(ServletRequest req, ServletResponse res, FilterChain filterChain) throws IOException,ServletException {

		HttpServletRequest request = (HttpServletRequest)req;
		HttpServletResponse response = (HttpServletResponse)res;

		String servletPath = request.getServletPath();
		HttpSession session = request.getSession();
		String flag = (String)session.getAttribute("flag");

		if (servletPath.equals("/Jsp/logon.jsp")||servletPath.equals("/Jsp/index.jsp")||servletPath.equals("/LoginServlet")) {
			filterChain.doFilter(req, res);
		}
		else {
			if(flag!=null&&flag.equals("login_success")){
				filterChain.doFilter(req, res);
			}
			else if (flag!=null && flag.equals("login_error")) {
				request.setAttribute("return_uri", servletPath);
				RequestDispatcher rd = request.getRequestDispatcher("/Jsp/login.jsp");
				rd.forward(request, response);
			}
			else {
				request.setAttribute("return_uri", servletPath);
			    RequestDispatcher rd = request.getRequestDispatcher("/Jsp/login.jsp");
			    rd.forward(request, response);
			}

		}

	}

	public void destroy() {

	}
}