<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">

  <display-name>netctoss</display-name>

  <welcome-file-list>

    <welcome-file>index.html</welcome-file>

    <welcome-file>index.htm</welcome-file>

    <welcome-file>index.jsp</welcome-file>

    <welcome-file>default.html</welcome-file>

    <welcome-file>default.htm</welcome-file>

    <welcome-file>default.jsp</welcome-file>

  </welcome-file-list>

  <servlet>

    <servlet-name>main</servlet-name>

    <servlet-class>web.MainServlet</servlet-class>

  </servlet>

  <servlet-mapping>

    <servlet-name>main</servlet-name>

    <url-pattern>*.do</url-pattern>

  </servlet-mapping>

   <!-- 声明发生哪种异常时转发到哪个错误的页面 -->

  <!--  注意，此处错误的页面的路径应该写绝对路径，而tomcat会主动帮我们加上项目名，

          所以此处的绝对就不要再写项目名，避免重复 -->

  <!-- 1.按照异常类型声明 -->

 <!--  <error-page>

              <exception-type>java.lang.Exception</exception-type>

              <location>/WEB-INF/error.jsp</location>

         </error-page> -->

  <!-- 2.按照异常的编号声明 -->

  <error-page>

    <error-code>404</error-code>

    <location>/WEB-INF/error.jsp</location>

  </error-page>

  <error-page>

    <error-code>405</error-code>

    <location>/WEB-INF/error.jsp</location>

  </error-page>

  <error-page>

    <error-code>500</error-code>

    <location>/WEB-INF/error.jsp</location>

  </error-page>

  <!-- 登录检查过滤器 -->

  <filter>

    <filter-name>login</filter-name>

    <filter-class>web.LoginFilter</filter-class>

  </filter>

  <filter-mapping>

    <filter-name>login</filter-name>

    <url-pattern>*.do</url-pattern>

  </filter-mapping>

</web-app>

package web;

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;

import javax.servlet.http.HttpSession;

public class LoginFilter implements Filter {

    public void destroy() {

    }

    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)

            throws IOException, ServletException {

        /*

         * 1.Filter由tomcat自动调用，tomcat会在接收到请求后，调用Servlet前调用Filter。

         * 2.tomcat在调用Filter前就会创建好request和response。

         * 3.tomcat实例化的是接口的实现类：

         *   RequestFacade implements HttpServletRequest

         *   HttpServletRequest extends ServletRequest

         */

        HttpServletRequest request=(HttpServletRequest) req;

        HttpServletResponse response=(HttpServletResponse) res;

        //排除掉3个不需要检查的路径，即发现是这3个路径，直接让请求继续执行

        String[] paths=new String[]{"/toLogin.do","/login.do","/createImg.do"};

        String p=request.getServletPath();//获取当前路径

        for(String path : paths){

            if(p.equals(path)){

                chain.doFilter(request, response);

                return;

            }

        }

        //从session获取账号

        HttpSession session=request.getSession();

        String adminCode=(String)session.getAttribute("adminCode");

        //根据账号判断用户是否登录

        if(adminCode ==null){

            //没登录，重定向到登录页

            response.sendRedirect("/netctoss/toLogin.do");

        }else{

            //已登录，请求继续执行

            chain.doFilter(request, response);

        }

    }

    public void init(FilterConfig cfg) throws ServletException {

    }

}