[]servlet中2个service方法有何区别

[求助]servlet中2个service方法有何区别？
1.protected void service(HttpServletRequest req,HttpServletResponse resp)throws ServletException,
IOException
2.public void service(ServletRequest req,HervletResponse res)throws ServletException,IOException

------解决方案--------------------------------------------------------
HttpServlet继承自GenericServlet,HttpServletRequest和HttpServletResponse分别继承自ServletRequest, ServletResponse.简单的说,就是第一个方法是HttpServlet的,第二个方法是GenericServlet的,HttpServlet因为继承了GenericServlet,所以继承了这个service方法.