安全性高、在服务端、存储空间大
缺点：让服务器运行缓慢
const express=require('express');
const cookieParser=require('cookie-parser');
const cookieSession=require('cookie-session');
var server=express();
server.use(cookieParser());
server.use(cookieSession({
keys:['aaa','bbbb','cccc']
}));
server.use('/',function(req,res){
console.log(req.session);
res.send('ok');
});
server.listen(8080);
