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
– Varkal, Commented May 13, 2015 at 12:12

Michael Shopsin · Accepted Answer · 2019-07-18 15:46:40Z

60

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, 2019 at 15:46

answered Jun 3, 2015 at 15:56

Michael Shopsin

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8 Comments

Aneil Mallavarapu Over a year ago

Slight typo. It should be: res.end(new Buffer(data), 'binary')

Idan Dagan Over a year ago

keep in mind that new Buffer() is deprecated and it have security issues.

Idan Dagan Over a year ago

@realtebo you can use Buffer.from() - see Node.js docs for more examples.

Seybsen Over a year ago

new Buffer() is deprecated, use Buffer.from() instead.

Prav Over a year ago

why use Buffer.from when data is binary, isn't that reserved for strings? wouldn't you have to use Buffer.alloc?

|

Ahmad Baktash Hayeri · Accepted Answer · 2017-01-01 07:32:26Z

35

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 1, 2017 at 7:32

Ahmad Baktash Hayeri

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answered May 13, 2015 at 14:49

Varkal

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4 Comments

dark_shadow Over a year ago

I tried same thing but it's not working for me. stackoverflow.com/questions/37517312/…

Nickolodeon Over a year ago

In what library does request lib reside for request(req.url).pipe(res)?

Dan Sterrett Over a year ago

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.

DDR Over a year ago

Request seems to come from npmjs.com/package/request, which is deprecated now. github.com/request/request/issues/3142

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