老師的代碼中沒有執行?chain.doFilter(request, response);那是怎么放行的？

@Override

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()+"/mian.jsp");

//轉發

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

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

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

}