long before = System.currentTimeMillis()；    ..........     long after = System.currentTimeMillis()； //规定了doFilter()负责拦截用户请求的过滤范围。

 

HttpServletRequest hrequest = (HttpServletRequest) request ;  //HttpServletRequest接口是ServletRequest子接口。这句话的意思是将请求强制转换为HttpServletRequest型再赋给HttpServletRequest 请求对象hrequest

 

System.out.println("Filter 已经拦截到用户的请求的地址: "  + hrequest.getServletPath());  //通过getServletPath()函数输出截获到用户的请求的地址。