Express-session返回'undefined'，即使我声明了session

Question

我已经在这个网站上工作了一段时间了，直到现在还没有遇到什么问题。

当用户登录时，一个会话cookie被初始化，这个cookie被称为user，并存储用户的电子邮件。当我在控制台上将cookie记录在登录post请求上时，就在我声明它之后，它显示数据，但是，当我更改路由(到任何其他) ex。主路由，cookie不是持久的，并且我的用户cookie更改为“未定义”。

Post请求，我使用firebase API进行身份验证：

// Login POST Route
router.post('/login', (req, res) => {
    // Firebase authentication service
    firebase_user.auth().signInWithEmailAndPassword(req.body.email, req.body.password).then(data => {
        // Cookie Init
        req.session.user = req.body.email;
        console.log(req.session.user); // In here, cookie shows desired value
    }).catch(err => {
        res.send({"error": err.message});
    });
});

主路由：

router.get('/home', (req, res) => {
    // Check if Session Cookie Exists
    if (req.session.user) {
        res.render('home.ejs');
    } else {
        res.redirect('/login');
        console.log(req.session.user); // This console log shows 'undefined' even tho there the cookie was initialized correctly
    }
});

中间件：

app.use(bodyParser.json());
app.use(morgan('combined'));
app.set('view engine', 'ejs');
app.use(express.static('./public'))
app.set('views', path.join(__dirname, 'views'));
app.use(bodyParser.urlencoded({ extended: true }));
app.use(cookieParser());
app.use(session({secret:"Testasl",resave:false,saveUninitialized:true,cookie:{secure:!true}}));

// Routes
app.use(routes);

下面是我如何将数据发送到login方法。我使用Axios和Vue：

var urlLog = 'http://localhost:3000/login';

new Vue({
    el: '#main',
    data: {
        email: '',
        password: '',
        showForm: true,
        showPreloader: false,
        errorMessage: '',
        errorShow: false

    },
    methods: {
        submitForm: function() {
            // Validates forms
            if (this.email!='' && this.password!=''){

                // Show Preloader
                this.showForm=false;
                this.showPreloader=true;

                // Ajax Post Request
                axios.post(urlLog, {
                    email: this.email,
                    password: this.password
                }).then(res => {
                    if (res.error){
                        // Shows form
                        this.showForm=true;
                        this.showPreloader=false;

                        // Shows Error
                        this.errorShow = true;
                        this.errorMessage = res.error;
                    } else {
                        // do nothing
                    }
                // Server Side error
                }).catch(err => {
                    console.log(err);
                });
            } else {
                this.errorShow = true;
                this.errorMessage = 'All fields are necessary...';   
            }
        }
    }
});

你知道为什么会这样吗？

*编辑*

更新:所以我一直在使用cookie，准确地说，是使用cookie解析器模块，我决定用它初始化cookie。并返回此错误消息：

Error: Can't set headers after they are sent.
    at validateHeader (_http_outgoing.js:491:11)
    at ServerResponse.setHeader (_http_outgoing.js:498:3)
    at ServerResponse.header (C:\Users\Thirsty-Robot\Desktop\Projects\Important\Robotics\Dashboard\node_modules\express\lib\response.js:767:10)
    at ServerResponse.append (C:\Users\Thirsty-Robot\Desktop\Projects\Important\Robotics\Dashboard\node_modules\express\lib\response.js:728:15)
    at ServerResponse.res.cookie (C:\Users\Thirsty-Robot\Desktop\Projects\Important\Robotics\Dashboard\node_modules\express\lib\response.js:853:8)
    at router.get (C:\Users\Thirsty-Robot\Desktop\Projects\Important\Robotics\Dashboard\bin\routes.js:74:9)
    at Layer.handle [as handle_request] (C:\Users\Thirsty-Robot\Desktop\Projects\Important\Robotics\Dashboard\node_modules\express\lib\router\layer.js:95:5)
    at next (C:\Users\Thirsty-Robot\Desktop\Projects\Important\Robotics\Dashboard\node_modules\express\lib\router\route.js:137:13)
    at Route.dispatch (C:\Users\Thirsty-Robot\Desktop\Projects\Important\Robotics\Dashboard\node_modules\express\lib\router\route.js:112:3)
    at Layer.handle [as handle_request] (C:\Users\Thirsty-Robot\Desktop\Projects\Important\Robotics\Dashboard\node_modules\express\lib\router\layer.js:95:5)

cookie是这样设置的：

// Login GET Route
router.get('/login', (req, res) => {
    res.render('log_in.ejs');
    res.cookie('idk', 'idksj');
    console.log(req.cookies);
});

Answer 1

正如您的错误所述，您不能在已经发送了头之后设置头。

在您的示例中，您将在结束响应后设置cookie标头：

// Login GET Route
router.get('/login', (req, res) => {
    res.render('log_in.ejs'); // completes the response
    res.cookie('idk', 'idksj'); // tries to set a cookie header
    console.log(req.cookies);
});

对于这种情况，您只需交换这两行代码就可以了：

// Login GET Route
router.get('/login', (req, res) => {
    res.cookie('idk', 'idksj');
    res.render('log_in.ejs');
    console.log(req.cookies);
});

尽管您可能只想在验证登录之后执行此操作(在此代码块中您实际上并没有执行此操作)