JavaWeb核心技术中Session与Cookie浅析

// 上面提到过用户的请求会携带cookie  所以要从客户端获取到cookie

Cookie[] cookies = req.getCookies(); // --返回Cookie数组

// 创建cookie  两个参数  键name   --   值value

Cookie cookie = new Cookie( "LoginTimes" ,System.currentTimeMillis()+ "" );

// 获取键

cookie.getName()

// 获取值

cookie.getValue()

// 设置Cookie有效期  --> 24*60*60表示24小时*60分钟*60秒

cookie.setMaxAge( 24 * 60 * 60 );

// 响应给客户端一个Cookie(信件)

resp.addCookie(cookie);

// 参考下方的doGet方法体

{

         // -- 显示上次访问的时间

         req.setCharacterEncoding( "UTF-8" );

         resp.setCharacterEncoding( "UTF-8" );

  resp.setHeader( "contenttype" , "text/html;charset=UTF-8" );

System.out.println( "resp编码：" +resp.getCharacterEncoding());

         System.out.println( "req编码：" +req.getCharacterEncoding());

         PrintWriter out = resp.getWriter();

         // 从客户端获取Cookie

         Cookie[] cookies = req.getCookies(); // --返回Cookie数组

         // 判断该用户是否已经存在Cookie

         if (cookies!= null ){

             out.write( "LastTime Login Time:" );

             for (Cookie cookie : cookies) {

                 // 遍历找到访问时间的Cookie  getName获得cookie中的键

                 if (cookie.getName().equals( "LoginTimes" )){

                     // 获取LoginTimes-Cookie的值  -- value

                     long l = Long.parseLong(cookie.getValue());

                     Date date = new Date(l);

                     out.write(date.toLocaleString());

                 }

             }

         }

         // 记录本次访问的时间  --> 新建Cookie

         Cookie cookie = new Cookie( "LoginTimes" ,System.currentTimeMillis()+ "" );

// 设置Cookie有效期  --> 24*60*60表示24小时*60分钟*60秒

         cookie.setMaxAge( 24 * 60 * 60 );

         // 响应给客户端一个Cookie(信件)

         resp.addCookie(cookie);

     }

// setCharacterEncoding意思是在程序中将请求和响应均置为utf-8编码 但是可能浏览器会无法解析

         req.setCharacterEncoding( "UTF-8" );

         resp.setCharacterEncoding( "UTF-8" );

// 浏览器使用的编码集可能与UTF-8不同  所以此处设置浏览器采用UTF-8编码

         resp.setHeader( "content-type" , "text/html;charset=UTF-8" );

// 编码

URLEncoder.encode( "张三" , "utf-8" );

// 解码

URLDecoder.decode( "李四" , "utf-8" );

/*源码解析：以秒为单位指定cookie的最大期限；如果否定，则表示未存储cookie；如果为零，则删除cookie

*/

resp.setMaxAge( 0 );

// Session对象

HttpSession session = req.getSession();

// session创建时间

out.write( "创建时间：" +session.getCreationTime()+ "\n" );

// sessionID获取

out.write( "SessionID:" +session.getId()+ "\n" );

// session上次访问时间

out.write( "上次访问时间：" +session.getLastAccessedTime()+ "\n" );

// setAttribute设置键值属性  getAttribute根据键获取值

// getValue 根据键获取值-->从2.2开始呗getA他tribute替代

// removeAttribute(String name) 删除name键绑定的对象 如果不存在则不执行任何操作

// isNew() 判断该Session是否为新创建的

//注销Session 

session.invalidate();

//注销Session也会注销掉SessionID

// Servlet 1

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

         // 编码问题

         req.setCharacterEncoding( "UTF-8" );

         resp.setCharacterEncoding( "UTF-8" );

         resp.setHeader( "content-type" , "text/html;charset:utf-8" );

         // 流

         PrintWriter out = resp.getWriter();

         // Session

         // -- 1.获取Session对象

         HttpSession session = req.getSession();

         // -- 2.获取SessionID

         String id = session.getId();

         // -- 3.判断该ID是否存在

         if (session.isNew()) {

             out.write( "SessionID已存在：" +id);

         } else {

             out.write( "Session创建成功，ID：" +id);

         }

         out.write( "<h1>数据已写出，跳转checkData查看</h1>" );

         // -- 4.写出数据

         session.setAttribute( "name" , "张三" );

     }

// Servlet  2

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

         // 编码

         req.setCharacterEncoding( "UTF-8" );

         resp.setCharacterEncoding( "UTF-8" );

         resp.setHeader( "content-type" , "text/html;charset=UTF-8" );

         // 获取数据

         HttpSession session = req.getSession();

         String name = (String) session.getAttribute( "name" );

         // 写出数据

         resp.getWriter().write( "name:" +name);

     }