无法设置未定义的属性“名称”

Question

所以我是 express（和整个后端）的新手，公平地说，我不知道如何使用 sessions（我首先使用 cookie，但后来我听说 sessions 是更好地维护用户的状态）所以我安装了express-session 并且确实像这篇文章一样：

https://stackoverflow.com/a/37608202/5737650

我将会话保存在变量中（sess），然后我用来获取信息，但问题是 sess 似乎只是 cookie 对象，而不是我需要保存的其他信息用户的输入给了我这个错误：

Cannot set property "name" of undefined

这是我的代码，它的工作是注册用户，将数据保存到数据库，然后当它进入登录页面时，它会检查他的输入是否存在于数据库中，如果不存在，那么它会给我一个 @ 987654329@，如果存在，那么它会将数据保存到会话中，以便我以后可以保持其状态，但是当我输入正确的输入时，它会给我上述错误：

// Importing modules/packages
let connection = require("./Connection.js");
let bodyParser = require("body-parser");
var cookieParser = require("cookie-parser");
let express = require("express");
let app = express();
var session = require("express-session");
app.use(cookieParser());
app.use(
  session({
    secret: "1E3ESS3DSS4DS4",
    saveUninitialized: true,
    resave: false,
    cookie: {
      path: "/",
      maxAge: 1000 * 60 * 60,
      httpOnly: true
    },
    user: {
      name: "",
      password: "",
      status: ""
    }
  })
);
let urlencodedParser = bodyParser.urlencoded({ extended: false });

// Server and routing
app.listen(3000, function() {});
app.set("view engine", "ejs");
app.get("/Signup", (req, res) => {
  res.render("Register");
});
app.get("/", function(req, res) {
  res.redirect("Login");
});
app.get("/Login", function(req, res) {
  res.render("Login");
});

// Database's Connection
connection.connect(err => {
  if (err) {
    throw "ERROR! " + err;
  }
});

// Requesting and Receiving Data from body parser
app.post("/Signup", urlencodedParser, function(req, res) {
  res.render("Register");
  connection.query(
    `insert into users (Username, User_Password, Email_Address) values ("${
      req.body.Username
    }", ${req.body.Password}, "${req.body.Email}")`,
    function(err) {
      if (err) throw "An error has happened while excuting the query " + err;
      console.log("Query got excuted successfully!");
    }
  );
});

app.post("/Login", urlencodedParser, (req, res) => {
  let sess = req.session;
  console.log(sess);
  connection.query(
    `SELECT Username FROM users WHERE User_Password = ? AND Username = ?`,
    [req.body.Password, req.body.Username],
    function(err, results) {
      if (results.length === 0) {
        console.log(
          "Sorry, this username/password doesn't exist in our database."
        );
      } else {
        console.log("Logined successfully!");
        sess.user.name = req.body.Username;
        sess.user.password = req.body.Password;
        sess.user.status = "online";
      }
      res.render("Login");
    }
  );
});

我如何解决这个问题并获得我想要的结果（保持其状态记录在整个网站上）？

Answer 1

代码中有几个错误。

1. 最初，会话对象不会有user 对象。因此sess.user 将是undefined。所以第一个错误Cannot set property "name" of undefined 是有道理的。您可能希望先将 sess.user 初始化为空对象。

2. 有了POST的请求，你需要调用req.session上的.save()来保存它。阅读更多关于它的信息here

这是我在我的机器上尝试过的代码：

app.post("/Login", (req, res) => {
    let sess = req.session;
    res.send(sess);
    sess.user = {};
    sess.user.name = req.body.Username;
    sess.user.password = req.body.Password;
    sess.user.status = "online";
    req.session.save();
});

你可以这样做：

app.post("/Login", urlencodedParser, (req, res) => {
    let sess = req.session;
    console.log(sess);
    connection.query(
        `SELECT Username FROM users WHERE User_Password = ? AND Username = ?`,
        [req.body.Password, req.body.Username],
        function(err, results) {
            if (results.length === 0) {
                console.log(
                    "Sorry, this username/password doesn't exist in our database."
                );
            } else {
                console.log("Logined successfully!");
                sess.user = {
                    name: req.body.Username,
                    password: req.body.Password,
                    status: "online"
                };
            }
            req.session.save();
            res.render("Login");
        }
    );
});