node.js Error: req.flash() requires sessions

Question

一个简单的node.js project， 我刚刚学习node，希望大家可以帮忙看一下
500报错信息

Running BAPS Version: 3.2.4
GET / 500 5.262 ms - 1396
Error: req.flash() requires sessions
    at IncomingMessage._flash [as flash] (/Users/chrischen/Documents/BAPS/baps_rest/node_modules/connect-flash/lib/flash.js:60:41)
    at ServerResponse.res.render (/Users/chrischen/Documents/BAPS/baps_rest/node_modules/express-flash/lib/express-flash.js:28:35)
    at /Users/chrischen/Documents/BAPS/baps_rest/BAPS.js:239:7
    at Layer.handle_error (/Users/chrischen/Documents/BAPS/baps_rest/node_modules/express/lib/router/layer.js:71:5)
    at trim_prefix (/Users/chrischen/Documents/BAPS/baps_rest/node_modules/express/lib/router/index.js:315:13)
    at /Users/chrischen/Documents/BAPS/baps_rest/node_modules/express/lib/router/index.js:284:7
    at Function.process_params (/Users/chrischen/Documents/BAPS/baps_rest/node_modules/express/lib/router/index.js:335:12)
    at next (/Users/chrischen/Documents/BAPS/baps_rest/node_modules/express/lib/router/index.js:275:10)
    at Layer.handle_error (/Users/chrischen/Documents/BAPS/baps_rest/node_modules/express/lib/router/layer.js:67:12)
    at trim_prefix (/Users/chrischen/Documents/BAPS/baps_rest/node_modules/express/lib/router/index.js:315:13)

BAPS.js (app.js)

var cookieParser = require('cookie-parser');
var flash = require('express-flash');
var sess = require('express-session');
var MySQLStore = require('express-mysql-session')(sess);
var expressValidator = require('express-validator');
var passport = require('passport');
const https = require("https"),
  fs = require("fs");
var mysql = require('mysql');
var app = express();

app.use(flash());
app.use(cookieParser());
app.use(expressValidator());

var connection = require('./connection');

//Store sessions on database
var sessionStore = new MySQLStore({}, connection);

app.use(sess({
  name: 'BAPSSESSION',
  secret: 'BAPSISGREAT',
  secure: true,
  store: sessionStore,
  resave: true,
  saveUninitialized: true,
  cookie: {
    //TODO: CHANGE THIS BACK TO 1000000000!
    maxAge: 365 * 24 * 60 * 60 * 1000 //one year
  }
}));

//Passport config(authentication)
require('./routes/config/passport')(passport);
app.use(passport.initialize());
app.use(passport.session());


module.exports = app;

Answer 1

参考GPT和自己的思路：

根据报错信息，“req.flash() requires sessions”提示 req.flash() 方法需要使用 session，而在你的代码中，使用了 express-session 作为 session 中间件。但是，需要注意的是，要在 req.flash() 使用之前，先使用 session 中间件，否则会报错。

所以，你需要确保在使用 req.flash() 方法之前，已经正确使用了 sess 中间件。并且，为了防止这种错误的发生，建议在 app.js 中间件的使用中，将 session 中间件的设置放在最前面，以确保它先于其他中间件执行。