Authentication for external download

Question

On my Community page, I'm trying to provide a download for a file that resides outside of Salesforce. I want the user to be authenticated prior to download and I don't want the user to know the URL of the file.

Currently, I have a link to a Visualforce page on the Community. An Apex controller checks for a PermissionSet and returns a PageReference with the URL of the file.

With this method, the URL of the file can be determined by any download manager.

Is there a way to accomplish this in Salesforce? Maybe I'm going about this the wrong way....

I did find this https://developer.salesforce.com/forums/ForumsMain?id=906F00000008w0oIAA , which lets me retrieve the file in Apex controller, but can I serve the Blob to the user as a file download?

Answer 1

Yes you can, using a href="data:" url.

You'll need to determine your mime type, using something like this (note the mimetype map is just for example sake - get yourself a better list):

String mimeType {get;set;}
String fileName = 'blabblay.bco.pdf';

Map<String,String> mimeTypeMap = new Map<String,String>{'pdf'=>'application/pdf','doc'=>'application/worddoc'};

String[] fileNameParts = fileName.split('\\.');
String ext = fileNameParts[fileNameParts.size()-1];

mimeType = mimeTypeMap.get(ext);

Once you have that, you can add this to your VisualForce page:

<a href="data:{!mimeType};content-disposition:attachment;base64,{!base64Value}">Download PDF</a>

Here's a list of mime types to save you a couple of clicks.