01_8_session

1. session总结

1.1服务器的一块内存(存key-value)

1.2和客户端窗口对应(子窗口)(独一无二)

1.3客户端和服务器有对应的SessionID

1.4客户端服务器端发送SessionID的时候两种方式

1. cookie(内存cookie)
2. rewrite URL

1.5浏览器禁掉cookie，就不能使用session（使用cookie实现session）

1.6如果想安全的使用session(不论客户端是否禁止cookie)，只能使用URL重写(大大增加编程负担)，很多网站要求客户端打开cookie

2.例子

2.1ShowSession.java

public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { response.setContentType("text/html; charset=utf-8");PrintWriter out = response.getWriter();String title = "Session Tracking Example";HttpSession session = request.getSession(true);String heading;Integer accessCount = (Integer) session.getAttribute("accessCount");System.out.println(accessCount);if (accessCount == null) {accessCount = new Integer(0);heading = "Welcom, Newcomer";System.out.println(accessCount);} else {heading = "Welcome Back";accessCount = new Integer(accessCount.intValue() + 1);}session.setAttribute("accessCount", accessCount);/*Integer access = (Integer) session.getAttribute("accessCount");System.out.println(access);*/out.println("");out.println("");out.println("  ");out.println("  ");out.print("
" + heading + "
");out.print("
Information on Your Session:
");out.println("
     
      
       
        
Info Type
        
Value
       
       
        
Creation Time
        
" + new Date(session.getCreationTime())+ "
       
       
        
Time of Last Access
        
" + new Date(session.getLastAccessedTime()) + "
       
       
        
Number of Previous Accesses
        
" + accessCount+ "
       
      
     
");out.println("  ");out.println("");out.flush();out.close();}

 

 

2.2SessionInfoServlet.java

public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { response.setContentType("text/html; charset=utf-8");PrintWriter out = response.getWriter();HttpSession session = request.getSession(true); out.println("");out.println("");out.println("  ");out.println("  ");out.print("
Session Information
");out.print("New Session:" + session.isNew());out.println("
Session ID:" + session.getId());out.println("
Session Creation Time:" + new Date(session.getCreationTime()));out.println("
Session Last Accessed Time:" + new Date(session.getLastAccessedTime()));out.println("
Request Information
");out.println("Session ID from Request:" + request.getRequestedSessionId());out.println("
Session ID Via Cookie:" + request.isRequestedSessionIdFromCookie());out.println("
Session ID Via rewritten URL:" + request.isRequestedSessionIdFromURL());out.println("
Valid Sesion ID:" + request.isRequestedSessionIdValid());out.println("  ");out.println("");out.flush();out.close();}

 

 

2.3URLSession.java

public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { response.setContentType("text/html; charset=utf-8");PrintWriter out = response.getWriter();HttpSession session = request.getSession(true);out.println("");out.println("");out.println("  ");out.println("  ");out.print("session id:" + session.getId() + "
");out.print("from url:" + request.isRequestedSessionIdFromUrl() + "
");out.print("from cookie:" + request.isRequestedSessionIdFromCookie() + "
");out.println(" test 
");out.println(" test 
");out.println("  ");out.println("");out.flush();out.close();}