express手工实现session原理

 var express = require('express');
 var cookieParser = require('cookie-parser');
 var bodyParser = require('body-parser');
 var app = express();
 app.use(bodyParser.json());
 app.use(bodyParser.urlencoded({ extended: false }));
 app.use(cookieParser())

 var sessions = {  };
 var key = ' session_id ';
 var EXPIRES = 20 * 60 * 1000;
 var generate = function(){
   var session = {};
   session.id = (new Date().getTime() + Math.random());
   session.cookie = {
     expire : new Date().getTime() + EXPIRES
   }
   sessions[session.id] = session;
   return session;
 }

 app.use("/",function(req, res,next){

   var id = req.cookies.id;
   if(!id){
     console.log("无ID");
     req.session = generate();
     console.log(req.session);
   }else{
     console.log("有ID");
     var session = sessions[id];
       if(session){
         console.log("有session");
         req.session = session;
       }else{
         req.session = generate();
       }
   }
   res.setHeader('Set-Cookie',['id='+req.session.id,'aaa="bbbb"','path=/', 'max-age=360000','expires='+req.session.cookie.expire]);
   next()

 });
 app.get("/",function(req,res){
   if(!req.session.isvist){
     req.session.isvist = true;
     res.send("第一次登陆")
   }else{
     console.log(sessions)
     res.send("再次登陆")
   }
 })

 app.listen(8080);

修正后：将app.use(“/”)改为app.use("*")

var express = require('express');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var app = express();
var user = require('./modules/user');
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));
app.use(cookieParser());

console.log(user);
var sessions = {  };
var key = ' session_id ';
var EXPIRES = 20 * 60 * 1000;
var generate = function(){
  var session = {};
  session.id = (new Date().getTime() + Math.random());
  session.cookie = {
    expire : new Date().getTime() + EXPIRES
  }
  sessions[session.id] = session;
  return session;
}

//通过中间件实现在每一个路由中都生成session
app.use("*",function(req, res,next){
  req.aa = "aaaaa";
  var id = req.cookies.id;
  if(!id){
    console.log("无ID");
    req.session = generate();
    console.log(req.session);
  }else{
    console.log("有ID");
    var session = sessions[id];
      if(session){
        console.log("有session");
        req.session = session;
      }else{
        req.session = generate();
      }
  }
  res.setHeader('Set-Cookie',['id='+req.session.id,'aaa="bbbb"','path=/', 'max-age=360000','expires='+req.session.cookie.expire]);
  next()

});
app.get("/",function(req,res){
  if(!req.session.isvist){
    req.session.isvist = true;
    res.send("第一次登陆")
  }else{
    console.log(sessions)
    res.send("再次登陆")
  }
})
app.get('/a',function(req,res){

})

app.listen(8080);

基本逻辑就是，用户进入路由先判断cookie中有没有ID；

没有Id的话生成一个新的session；

有ID的话根据ID去内存或数据库查找session

若没有session生成一个新的session；

若有session查看其过期时间，若过期生成新的session

若没有过期，更新其时间；

最后将session赋值给req.session；

这样在其他路由里就可以访问session了，并且req.session可以挂载任何属性，比方说用户登录后将用户信息挂载到req.session上