Download a stream directly from the database

This code snippet provides a ZEN page that downloads a stream from its database directly:

/// We assume that you have stored your data within this schema:
/// MyApp.Model.Storage: Filename,FileSize,Content,ContentType
Class zen.downloadStream Extends (%ZEN.Component.page,%CSP.StreamServer)
{
/// Wrapper to get the id of the download, we assume that the id is passed to this zen page
/// as a URI parameter, i.e.: MyApp.Downloads.cls?OID=1234
ClassMethod GetId()
{
    Quit $Get(%request.Data("OID",1))
}
 
/// Set the appropriate header for the file.
ClassMethod OnPreHTTP() As %Boolean
{
    Set tId = ..GetId()
 
    If ##Class(MyApp.Model.Storage).%ExistsId(tId) {
        Set tStream = ##Class(MyApp.Model.Storage).%OpenId(tId)
        // You could "guess" the content type by its file extension
        // or you can store it (before) in the database separately (like in this example).
        // Set Extension = $Piece(tStream.Filename,".",$Length(tStream.Filename,"."))
        // Set ContentType = ..FileClassify(Extension)
 
        Set %response.ContentType = tStream.ContentType
        Do %response.SetHeader("content-disposition","attachment; filename="_tStream.Filename)
        Do %response.SetHeader("Content-Length",tStream.FileSize)
    }
    Else {
        Set %response.Status="404 File Not Found"
        Quit 0
    }
    Quit $$$OK
}
 
ClassMethod OnPage() As %Status
{
    Set Download = ##Class(MyApp.Model.Storage).%OpenId(..GetId())
    Do Download.Content.OutputToDevice()
    Quit $$$OK
}

}

Link to code on GitHub