HttpSession:会话跟踪

public void doPost(HttpServletRequest request, HttpServletResponse response)    throws ServletException, IOException

{

　 response.setContentType("text/html"); 

 //创建一个HttpSession   HttpSession session=request.getSession();

//回话的使用：session.setAbttribute(String name,Object value);保存一个对象

//session.getAbttribute(String name);取出保存对象，注意：返回类型是Object

　Object counter=session.getAttribute("COUNT");

　int count=0;

if(counter==null){

　count=1;

　session.setAttribute("COUNT",new Integer(1));

}else{

//intValue()将Integer类型转换成int类型

　count=((Integer)counter).intValue();

　count++;

　session.setAttribute("COUNT", new Integer(count));

   }

PrintWriter out=response.getWriter();

   out.print("欢迎你第"+count+"次访问");

   out.flush();

   out.close();

  }