node.js - Cannot read property 'end' of undefined - MySQL , NodeJS

Question

I want to show you my error with NodeJS and MySQL. Error is at line 45 of app.js

Cannot read property 'end' of undefined
at ServerResponse.<anonymous> (/usr/my_server/app.js:45:24)

It happen when I call a request from 'addReferFriend.js' file. I link here the two files that I am using.

app.js:

var express = require('express');
var path = require('path');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var mysql= require('mysql2');
var http = require('http');
var app = express();

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

app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'ejs');

app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));


app.use(async function(req, res, next) {
  try {
    if( req.dbConnection ) {
      // ensure that req.dbConnection was not set already by another middleware
      throw new Error('req.dbConnection was already set')
    }

    let connection = mysql.createConnection({
            host: 'xx',
        user: 'xx',
        password: 'xx',
        database: 'xx'
    });

    res.on("finish", function() {
      // end the connection after the resonponse was send
      req.dbConnection.end()
    });

    // wait for the connection and assign it to the request
    req.dbConnection = await connection.connect();
    next();
  } catch(err) {
    next(err);
  }
});

app.use('/api/addReferFriend', addReferFriend);

// catch 404 and forward to error handler
app.use(function(req, res, next) {
  var err = new Error('Not Found');
  err.status = 404;
  next(err);
});

module.exports = app;
var server = http.createServer(app);
server.listen(3955);

addReferFriend.js:

var express = require('express');
var router = express.Router();

/* GET users listing. */
router.post('/', function(req, res, next) {
  var uid = req.body.uid;
  var friendReferCode = req.body.friendReferCode;

  var sqlCheckIfExist = "SELECT my_refer FROM hub_user WHERE my_refer = '" + friendReferCode + "'";
  var sqlCodeCheckSameAsMine = "SELECT my_refer FROM hub_user WHERE uid = '" + uid + "'";

  function checkIfUserCodeExist() {
    return req.dbConnection.query(sqlCheckIfExist)
      .then(([rows, fields]) => {
        if (rows == 0) {
          console.log("Non esiste!")

          return res.send(JSON.stringify({
            "status": 500,
            "response": "codeNotExist"
          }));
        }
        console.log("Esiste!")
        return checkIfCodeIsSameAsMine(connection)
      })
  }

  function checkIfCodeIsSameAsMine() {
    return req.dbConnection.query(sqlCodeCheckSameAsMine)
      .then(([rows, fields]) => {
        if (rows == friendReferCode) {
          console.log("Codice uguale!")
          return res.send(JSON.stringify({
            "status": 500,
            "response": "sameCodeAsMine"
          }));
        }
        console.log("Codice non uguale!")
      })
  }

  checkIfUserCodeExist()
   .catch(next)
});
module.exports = router;

I have no idea how fix this type of problem. It happen when I call the checkIfUserCodeExist() and it doesn't join into the function and it gives directly the error. I can't print any of console.log because it break.

Hope that somebody can help me with this issue. Thanks in advance for the help, Michele.

Answer 1

it seems to be req.dbConnection.end() the problem... the object dbConnection is undefined.

is it possible that the connection is closed first for some reason? so the point to closing connection is not correct?