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

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