如何让我的 Node.js MySQL 连接作为承诺工作？

Posted 2023-02-24

【中文标题】如何让我的 Node.js MySQL 连接作为承诺工作？

【英文标题】：How can I make my Node.js MySQL connection as a promise work?

【发布时间】：2020-07-10 16:25:09

【问题描述】：

刚开始接触node.js，js知识有点生疏。

我从回调开始，然后我发现了 Promise。这种语法更像是我的大脑工作，所以我用 Promise 重写了我的代码。 但现在我的 mysql 连接不起作用。它甚至无法到达（我认为...） 我已经在文件 userDB 中记录了“test”这个词，它起作用了。但随后在 mySql 文件中，console.log "test2" 不起作用。

谢谢大家！ 克里斯

这是我的 server.js（节点启动的文件）：

/* 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`)
)

这是我的路由器文件 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

这是我的用户数据库文件：

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))
    )

这是我的用户中间件（这是中间件吗？）：

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,
        )

最后但并非最不重要的是我的 mySql.js 文件：

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;

【参考方案1】：

您的 mySql.js 文件中有一个简单的错字：

线

var mySql = require('mysql');

应该替换为

var mysql = require('mysql');

除了查询代码在我的机器上运行正常：

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;

【讨论】：

太好了，很高兴为您提供帮助。我相信你在回调上使用 Promises 是正确的，当你说“这种语法更像我的大脑工作”时，你说得很好:)。另请查看 async / await 语法，这又更具可读性。见developer.mozilla.org/en-US/docs/Web/javascript/Reference/…。