Express - Return binary data from webservice

Question

I try to return some binary data with Express. In the example, it's a PDF but theorically, this can be any sort of file.

But focus on the pdf for the moment. I wrote this code :

app.get('*', function (req, res) {
    getBinaryData(req.url,
        function (answer) {
            res.type('pdf');
            res.end(new Buffer(answer, 'binary'));
        },
        function (error) {
            res.setHeader('Content-Type', 'text/plain');
            return res.end(error);
        }
    );
});

Based on what I saw here : https://github.com/strongloop/express/issues/1555

But, i get a pdf file with the right number of pages, right title.... but all the pages are blank

I'm sure concern the return of getBinaryData(), because this function asked an external Web Service and when I asked directly this service, I got the right document.

Thank you in advance for your answers

cause I don't have the file : I get this binary content from another WebService. Eventually, I can create a temp file and use sendFile... — Varkal, May 13 '15 at 12:12

Michael Shopsin · Answer 1 · 2019-07-18T15:46:40.790

56

Here is my slightly cleaned up version of how to return binary files with Express. I assume that the data is in an object that can be declared as binary and has a length:

exports.download = function (data, filename, mimetype, res) {
    res.writeHead(200, {
        'Content-Type': mimetype,
        'Content-disposition': 'attachment;filename=' + filename,
        'Content-Length': data.length
    });
    res.end(Buffer.from(data, 'binary'));
};

edited Jul 18 '19 at 15:46

answered Jun 03 '15 at 15:56

Michael Shopsin

2,055
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Slight typo. It should be: `res.end(new Buffer(data), 'binary')` – Aneil Mallavarapu Dec 14 '17 at 14:00
1

keep in mind that new Buffer() is deprecated and it have security issues. – Idan Dagan Feb 18 '18 at 17:11
@IdanDagan: what could we use instead of `new Buffer()`? – realtebo Jan 04 '19 at 17:54
2

@realtebo you can use Buffer.from() - see Node.js docs for more examples. – Idan Dagan Jan 05 '19 at 14:23
3

`new Buffer()` is deprecated, use `Buffer.from()` instead. – Seybsen Jul 18 '19 at 09:16
1

why use Buffer.from when data is binary, isn't that reserved for strings? wouldn't you have to use Buffer.alloc? – Prav Jan 29 '20 at 19:34
What is the significance of using `.end()` instead of `.send()` with these examples? – NamedArray Aug 05 '21 at 19:37
@NamedArray `.end()` makes sure the connection is closed after the file is sent. `.send()` leaves the connection open using up a TCP socket. – Michael Shopsin Aug 09 '21 at 14:09

score 34 · Accepted Answer · edited Jan 01 '17 at 07:32

34

I found a more simple solution :

request(req.url).pipe(res);

This pipes the original response from distant Web Service directly to my response! I got the correct file regardless of the file type.

edited Jan 01 '17 at 07:32

Ahmad Baktash Hayeri

5,802
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answered May 13 '15 at 14:49

Varkal

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I tried same thing but it's not working for me. http://stackoverflow.com/questions/37517312/issue-while-requesting-a-fileimage-pdf-excel-sheet-from-server-and-then-pipe-t – dark_shadow May 30 '16 at 12:38
8

In what library does request lib reside for request(req.url).pipe(res)? – Nickolodeon Jun 08 '18 at 16:21
2

For everyone wondering what library `request` comes from, it's a built in node module, so just add `const request = require('request');` before the call. – Dan Sterrett Dec 15 '21 at 21:50

Express - Return binary data from webservice

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