import java.io.IOException;

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;

public class GrantFilter implements Filter {
    
    public void destroy() {
        System.out.println("GrantFilter Filter destroy...");

}

public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest) request;
        HttpServletResponse resp = (HttpServletResponse) response;
        String conString = "";
        conString = req.getHeader("REFERER");//获取父url--如果不是直接输入的话就是先前的访问过来的页面，要是用户输入了，这个父url是不存在的
        if("".equals(conString) || null==conString){ //判断如果上一个目录为空的话，说明是用户直接输入url访问的
         String servletPath = req.getServletPath();//当前请求url，去掉几个可以直接访问的页面
         if(servletPath.contains("index.jsp") || servletPath.contains("login.jsp")){ //跳过index.jsp和登陆Login.jsp
          chain.doFilter(request, response);
         } else {
          resp.sendRedirect("login.jsp");//跳回首页
         }
        } else {
         chain.doFilter(request, response);
        }
        
    }

public void init(FilterConfig config) throws ServletException {
        /*web.xml中Filter的配置参数*/
    }

}