HowTo: Download a file using HTTP Protocol

This article describes how to manage file downloads easily in your application.

If you want a user event to prompt the user to save or run a file like the following:

All you need to do is:

• Create a Procedure with the following property values:
  • Main program property = TRUE
  • Call protocol property = HTTP

To add data to the Http response header, the GeneXus object should be callable using the Http protocol. To make a procedure callable by the Http protocol, the above setting is necessary.
Below is a sample for downloading a file.

Procedure Source

/*
Get &contenttype, &filename and &filepath from the context (Websession, Database, etc). 
Do not receive them via parm because of security reasons (Path transversal).
*/
&HttpResponse.AddHeader(!"Content-Type", &contenttype) //&contenttype could be 'application/x-zip-compressed'
&HttpResponse.AddHeader(!"Content-Disposition", !"attachment;filename="+&filename) //&filename could be 'download.zip'
&HttpResponse.AddFile(&filepath) //&filepath could be 'C:\temp\download.zip'
&HttpResponse.AddHeader(!"Pragma", !"public")
&HttpResponse.AddHeader(!"Cache-Control", !"max-age=0")

How to Call the Download within GeneXus:

Event 'Download'
  ProcedureHTTPDownload.Link()   
EndEvent

Considerations

Be sure that the application has full access to &filepath. It will fail if the application cannot access to the &filepath (if not, it will throw Access Denied Exception)

See Also

Call protocol property