How can I make my Node.js MySQL connection as a promise work?

Christopher Smith :

I have just started to work with node.js and my js knowledge is a bit rusty.

I started with callbacks and then I found out about promises. This syntax was more like my brain works, so I rewrote my code with promises. But now my MySql connection does not work. It can't even get reached (I think...) I have logged the word "test" in the file userDB, that worked. But then in the mySql file the console.log "test2" didn't work.

Thanks to you all! Chris

Here is my server.js (the file that node starts):

/* REQUIRE */
const oAuth2Server = require('node-oauth2-server');
const express = require('express');
const bodyParser = require('body-parser');
const oAuthModel = require('./endpoints/auth/authModel');
const util = require('util');
const dbCon = require('./subsystem/mySql')

/* CONST */
const port = 3000;
const debug = true;
const app = express();

/* INIT */
app.oauth = oAuth2Server({
    model: oAuthModel,
    grants: ['password'],
    debug: debug
})

/* ROUTER */
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));
app.use(app.oauth.errorHandler());


const authRoutes = require('./router/auth')(express.Router(), app, dbCon)
app.use('/auth', authRoutes);

app.all('*', (req, res) => {
    res.status(404).send({message: "This service was not found"});
});




/* Start Server */
app.listen(port, () => {
    console.log(`listening on port ${port}`)
})

Here is my router file auth.js:

module.exports =  (router, expressApp, dbCon) => {
    const userDB = require('../endpoints/user/userDB')(dbCon)
    const authMiddleware = require('../endpoints/auth/authMiddleware')
    const userMiddleware = require('../endpoints/user/userMiddleware')(userDB)

    router.post('/registerUser', userMiddleware.registerUser)

    //router.post('/login', expressApp.oauth.grant(), authMiddleware.login)
    router.post('/login', expressApp.oauth.grant())
    return router
}

Here is my userDB file:

let mySqlConnection;

module.exports = injectedMySqlConnection => {

    mySqlConnection = injectedMySqlConnection

    return {

        registerUserInDB: registerUserInDB,
        getUserFromCrentials: getUserFromCrentials,
        doesUserExist: doesUserExist,
        getUserByUsername: getUserByUsername
    }
}

const registerUserInDB = (username, password) => {
    return new Promise((resolve,reject) => {
        //execute the query to register the user
        mySqlConnection.query(`INSERT INTO users (username, user_password) VALUES ('${username}', SHA('${password}'))`)
        .then(data => {resolve(true)})
        .catch(error => {reject(error)})
    })
}

const getUserFromCrentials = (username, password) => {
    return new Promise((resolve,reject) => {
        //create query using the data in the req.body to register the user in the db
        const getUserQuery = `SELECT * FROM users WHERE username = '${username}' AND user_password = SHA('${password}')`

        console.log('getUserFromCrentials query is: ', getUserQuery);

        //execute the query to get the user
        mySqlConnection.query(getUserQuery)
        .then(data => {resolve(data)})
        .catch(error => {reject(error)})
    })
}

const doesUserExist = username => {
    return new Promise((resolve,reject) => {
        console.log('test');
        //execute the query to check if the user exists
        mySqlConnection.query(`SELECT * FROM users WHERE username = '${username}'`)
        .then(data => {resolve(data.results !== null ? data.results.length == 1 ? true : false : false)})
        .catch(error => {reject(error)})
    })
}

const getUserByUsername = username => {
    return new Promise((resolve,reject) => {
        //execute the query to check if the user exists
        mySqlConnection.query(`SELECT id, username FROM users WHERE username = '${username}'`)
        .then(data => {resolve(data)})
        .catch(error => {reject(error)})
    })
}

Here is my userMiddleware (is this middleware?):

let userDb;

module.exports = injectedUserDb => {
    userDb = injectedUserDb
    return {
        registerUser: registerUser
    }
}

function registerUser(req, res){

    console.log(`authRoutesMethods: registerUser: req.body is:`, req.body);

    //query db to see if the user exists already
    userDb.doesUserExist(req.body.username)
    .then(data => {
        if(data)
        {
            sendResponse(res, "User already exists", 200)
            return
        }
        else
        {   
            //register the user in the db
            userDb.registerUserInDB(req.body.username, req.body.password)
            .then(data => {
                userDb.getUserByUsername(req.body.username)
                .then(data => {sendResponse(res,  data.results, "")})
                .catch(error => {sendResponse(res, "Failed to register user", error)})

            })
            .catch(error => {sendResponse(res, "Failed to register user", error)})
        }
    })
    .catch(err => {
        sendResponse(res, "User already exists", 200)
        return
    })
}


function sendResponse(res, message, error) {

    res
        .status(error !== null ? error !== null ? 400 : 200 : 400)
        .json({
            'message': message,
            'error': error,
        })
}

And last but not least my mySql.js file:

var mySql = require('mysql');

const query = sql => {
    return new Promise( ( resolve, reject ) => {
        let connection = mysql.createConnection({
            host: 'localhost',
            user: 'root',
            password: '',
            database: 'oauth2test'
        });
        console.log('test2');
        connection.query( sql, ( err, rows ) => {
            if ( err )
            {
                connection.end();
                reject( err );
            }
            else
            {
                connection.end();
                resolve( rows );
            }
        });
    });
}

module.exports.query = query;

Terry Lennox :

You have a simple typo in your mySql.js file:

The line

var mySql = require('mysql');

should be replaced with

var mysql = require('mysql');

Other than that the query code works ok on my machine:

var mysql = require('mysql');

const query = sql => {
    return new Promise( ( resolve, reject ) => {
        let connection = mysql.createConnection({
            host: 'localhost',
            user: 'root',
            password: '',
            database: 'oauth2test'
        });
        console.log('test2');
        connection.query( sql, ( err, rows ) => {
            if ( err )
            {
                connection.end();
                reject( err );
            }
            else
            {
                connection.end();
                resolve( rows );
            }
        });
    });
}

module.exports.query = query;

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