public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {

System.out.println("start----doFilter--FirstFilter");

//chain.doFilter(request, response);

HttpServletRequest req =(HttpServletRequest) request;

HttpServletResponse response2 =(HttpServletResponse) response;

//重定向

// response2.sendRedirect(req.getContextPath()+"/index.jsp");

//转发

req.getRequestDispatcher("index.jsp").forward(request, response);

// req.getRequestDispatcher("main.jsp").include(request, response);

System.out.println("end------doFilter--FirstFilter");

}

配置文件：

<welcome-file-list>

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

  </welcome-file-list>

  <filter>

      <filter-name>Filter</filter-name>

       <filter-class>FirstFilter.firstFilter</filter-class>

         </filter>

  <!--

  <filter-mapping>

   <filter-name>Filter</filter-name>

   <url-pattern>/index.jsp</url-pattern>

    <dispatcher>REQUEST</dispatcher>  

  </filter-mapping>

  -->

   <filter-mapping>

   <filter-name>Filter</filter-name>

   <url-pattern>/index.jsp</url-pattern>

    <dispatcher>FORWARD</dispatcher>  

  </filter-mapping>

</web-app>

控制台执行了init()  但是执行index.jsp并没有打印dofilter方法