res.download 仅在一条快速路线中未设置正确的标头

Question

I have a main express route that once navigated to, should prompt a download of the specified file in res.download:

app.get('/download/:fileid', (req, res) => {
    var connection = mysql.createConnection({
        host     : 'localhost',
        user     : 'root',
        password : '',
        database : 'filesystem'
      });

    connection.connect(() => {
        console.log("Connection to database established");

    });
    connection.query(`SELECT * from files where fileid = '${req.params.fileid}'`, (error, results, fields) => {
        if (error) throw error;
        else if(results.length === 0){
            console.log("empty");
        }
        else{
            res.download(`./uploads/PFSk5x7bg.png`, 'PFSk5x7bg.png', (err) => {
                console.log(err);
            })
        }
    });

    connection.end();
})

However, when accessed, it simply displays the image on the webpage, and when I check the response headers, the content disposition header is missing. I have tried manually setting it with res.setheader, but still does not work.

I tried making another route just for testing:

app.get('/test', (req, res) => {
    res.download(`./uploads/PFSk5x7bg.png`, 'PFSk5x7bg.png', (err) => {
        console.log(err);
    })
})

and it works.... the content disposition header is there, the browser actually downloads the file.

Is anyone able to understand what I am doing wrong with my /download route?

***UPDATE: I changed the name of the /download/:fileid route to /test/:fileid and it worked. I then changed it BACK to /download/:fileid and it now works... does anyone have any idea what could of caused this?

Answer 1

You have a few errors there, which can screw your debugging.

1. You have misplaced your connection.end() statement which will be called immediately after connection.query() . You should move it inside of connection.query 's callback.

2. Using relative paths instead of abolute ones. Try changing './uploads/PFSk5x7bg.png' to __dirname + '/uploads/PFSk5x7bg.png'

3. Not using res.end() in the request where necessary may confuse browser's representation of response of your software.

    if (error) { res.end(); throw error; }else if(results.length === 0){ res.end(); console.log("empty"); } else{ res.download(`./uploads/PFSk5x7bg.png`, 'PFSk5x7bg.png', (err) => { console.log(err); }) }