ZEN

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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

Last comment 11 days ago
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Hi All
This is the index to a series of articles I hope to create over the coming months.

ZEN and ZEN Mojo are no longer being actively developed by Intesystems - this is a great shame as it is a fine product that works so well for business applications.
However ZEN is a 15 year old product and I need a path forward to replace the ZEN UI with a supported development framework.

This article is an index of the other articles I have, or plan to write. - the articles will be subject to change as I develop my thoughts and climb the learning curve.

Last comment 12 May 2018
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Index to Articles

Published 2018-05-11 Last edit -

Hi All

I this article I detail some strategic issues that a new development UI will need to address - these are the ones that I can think of now - others may come to light during this journey.

See the webinar by Eduard Lebedyuk here from the last Global Summit describing  modern web development and Caché

And, as always, if I have missed something please comment....

Last comment 12 May 2018
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Index to Articles

Hi All

It's been 6 weeks since my original article sad
- - - - -but I have been busy on this project smiley

I have been looking at/thinking about a replacement for ZEN for around 12 months but only really started in depth 4 months ago.
Also been in IT for long enough that I can "get a feel" for a product/technology and make decisions accordingly without going into great detail. 
Any new technology has a learning curve and I don't want to waste time and effort on something that won't fly. 
And, as always, I am looking to minimise the learning curve as I want to concentrate on delivering business benefit. 

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