How to download a file when a django function is called by javascript instead of navigation to the url?

[Joel Mathew]

I have a page where several buttons process different functions like sending a user sms (via API), sends an file by email, or downloads a PDF file. Button actions dont use forms, but uses ajax requests via javascript.

I used to create a pdf file using javascript (jspdf), but have written code which generates a pdf file by python on the server. Now I need to allow download when the button is clicked.

Server code snippet:

    with NamedTemporaryFile(mode='w+b') as temp:

        from django.http import FileResponse

        doc = SimpleDocTemplate(temp.name, pagesize=A4, rightMargin=20, leftMargin=20, topMargin=20, bottomMargin=20, allowSplitting=1, title="Prescription", author="MyOPIP.com")

        doc.build(elements)

        print(f'Generated {temp.name}')

        return FileResponse(open(temp.name, 'rb'), content_type='application/pdf')

The above code is supposed to download a pdf file, if called ny navigating to the url.

On my javascript side, I tried to determine what I'm receiving:

    $.ajax({

        url: `/clinic/${cliniclabel}/prescription/download/patient/${patient_id}`,

        dataType: "html",

        data: data,

        type: 'POST',

        success: function (data) {

            console.log("Received data from server..type is ", typeof(data))

            console.log(data)

        }

    });

And I get:

    Received data from server..type is  string

    userjs/main.js:2067 %PDF-1.4

    %���� ReportLab Generated PDF document http://www.reportlab.com

    1 0 obj

    <<

    /F1 2 0 R /F2 5 0 R

    >>

    endobj

    2 0 obj....

Apparently django sends this as a file stream. How can I get the file downloaded to the user when the response is processed by javascript?

Sincerely yours,

Dr Joel G Mathew

[Jason]

check out https://stackoverflow.com/questions/4545311/download-a-file-by-jquery-ajax

[Joel Mathew]

Hi Jason,

Thank you for responding. 

I solved this by implementing a temporary link system in my model. This would generate a unique key which points to a foreign key which references the data I want. When the url with this foreign key is clicked, the pdf is generated on the fly and presented as a FileResponse. On the javascript side, what I do is generate the link when the button is clicked, and insert a Download button in the DOM and the href is set to the link presented by django.

Sincerely yours,

Dr Joel G Mathew

On Sat, 17 Nov 2018 at 19:16, Jason <jjohn...@gmail.com> wrote:

check out https://stackoverflow.com/questions/4545311/download-a-file-by-jquery-ajax

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[Jason]

not a bad solution, but you could most likely make the link generator/decoder work in your view handler rather than needing to hit the database.  That would prevent the necessity of some method to clean up the db of old temp links that are no longer valid.

[Yavin Aalto Arba]

did you try to set "as_attachment=True" ?

[Joel Mathew]

Where?

Sincerely yours,

Joel G Mathew

On Sat, 17 Nov 2018 at 20:50, Yavin Aalto Arba <yavi...@gmail.com> wrote:

did you try to set "as_attachment=True" ?

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[Jason]

oh, I didn't know that was a thing.  TIL.

https://docs.djangoproject.com/en/2.1/ref/request-response/#django.http.FileResponse

note the bit about as_attachment setting content disposition

[Joel]

Yes. But it's not usable when we're using JavaScript to fetch the url.

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[Yavin Aalto Arba]

will work with window.location=  

[Andréas Kühne]

If you use a windows.location solution, you will get the native solution for downloading files in the browser - which usually is to download the file to the downloads location (if you use attachment=True). I would prefer that than to having to create the file and link to it, or to save it via JS (which is also possible).

Regards,

Andréas

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