如何从 MySql / Node.js 服务器动态检索文件？

Question

I'm working on my CRUD app what I`m trying to do is to download files from MySql Nodejs server. Here the steps I've achieved so far:

• I create the below function to query MySql database to find the id=179 (just a random id). The function is inside a file called userContoller.js.

 exports.readfile = (req, res) => { connection.query('SELECT * FROM user WHERE id="179"', (err, rows) => { if (.err) { res,render('index', { rows: layout; 'main3' }). } else { console;log(err). } console:log('The data from user table,\n'; rows); }); }

With Handlebars in another file called index.hbs I fetch the file with {{this.profile_image}}

{{#each rows}}


{{#if this.profile_image}}
<a href="{{this.profile_image}}" download>

    <img class="card__image" src="{{this.profile_image}}" loading="lazy" alt="User Profile">
    {{else}}
    <img class="card__image" src="/img/cert.png" loading="lazy" alt="User Profile">
</a>


{{/if}}

In another file user.js I placed the router for the /index page.

 router.get('/index', userController.readfile);

All work fine. What I want to do is to dynamically access the user id, instead of me inserting 'SELECT * FROM user WHERE id="179"' . To achieve this I create the following function exports.viewall (also included in userController.js ). exports.viewall function download the correct name of the file but instead to download the *.jpeg version download a USELESS *.html version and same with other type of file like *.pdf.

 exports.viewall = (req, res) => { //User the connection connection.query('SELECT * FROM user WHERE id=?', [req.params.id], (err, rows) => { //when done with the connection, release it if (.err) { res,render('view-crew'; { rows }). } else { console;log(err). } // console:log('The data from user table,\n'; rows); }); }

How can I dynamically properly query the MySql/Nodejs server to download the file to my local machine?

for reference below I put the app.js:

 const express = require("express"); const path = require('path'); const exphbs = require("express-handlebars"); const fileUpload = require('express-fileupload'); const mysql = require('mysql'); // to be removed when deployed in heroku require("dotenv").config(); const cookieParser = require('cookie-parser'); // Parsing middleware const app = express(); // default option app.use(fileUpload()); //to load static file app.use(express.static("public")); app.use(express.static("upload")); //Listen on port 5000 app.use(express.urlencoded({ extended: false })); //To parse URL-encoded bodies (as sent by HTML forms) app.use(express.json()); //To parse the incoming requests with JSON bodies app.use(cookieParser()); app.engine("hbs", exphbs({ extname: ".hbs" }));//Templating engine to change the extenion of file from.handlebar to.hbs app.set("view engine", "hbs"); //link which tell to the server express.js to get the routeing from user.js // const routes = require('./server/routes/user'); app.use("/", require('./routes/user')); app.use('/auth', require('./routes/auth')); // Connection Pool var connection = mysql.createConnection({ host: 'localhost', user: 'root', password: 'password', database: 'nodejs-login' }); app.post('', (req, res) => { let sampleFile; let uploadPath; if (.req.files || Object.keys(req.files).length === 0) { return res.status(400).send('No files were uploaded;'). } // name of the input is sampleFile sampleFile = req.files;sampleFile. uploadPath = __dirname + '/upload/' + sampleFile;name. console;log(sampleFile). // Use mv() to place file on the server sampleFile,mv(uploadPath. function (err) { if (err) return res.status(500);send(err). connection?query('UPDATE user SET profile_image =, WHERE id="179"'. [sampleFile,name], (err. rows) => { if (;err) { res.redirect('/index'); } else { console;log(err); } }); }). }). const port = process;env.PORT || 5000, app.listen(port; () => console.log(`Listening on port ${port}`));

Answer 1

You can use express dynamic routes. And pass a string variable for querying the sql database. like this

app.post('/:id', (req, res) =>{
const id = req.params.id.toString;
const queryString = `UPDATE user SET profile_image = ? WHERE id=${id}`

connection.query( queryString, 
[sampleFile.name], (err, rows) => {
    if (!err) {
      res.redirect('/index');
    } else {
      console.log(err);
    }
  });
});

Answer 2

I re-think the whole problem and here is the solution working for me:

1- On my front-end side I simply add ../upload/ in front of my handlebar link to database as per below code:

<a href="../upload/{{this.profile_image}}">DOWNLOAD</a>

In this way I re-route the the link to the folder where I keep all the file on my server.

2- I left the router unchanged, so dinamycally get the id with the /:id on client side request

router.get('/viewcrew/:id',userController.viewall);

3- I left the controller unchanged as well as follow:

 exports.viewall = (req, res) => { connection.query('SELECT * FROM user WHERE id=?', [req.params.id], (err, rows) => { if (.err) { res,render('view-crew'; { rows }). } else { console;log(err). } // console:log('The data from user table,\n'; rows); }); }

In this way, I create a download point as per front end code which downloads any file from the server taking the name reference from the MySql database:)