Question

I have saved an image to a byte[] in a command object and wish to display it in the next stage of the createFlow webflow.

I am trying to steer clear of using the file system and / or database system for storing the image during the webflow.

Typically, to view the image, I would call renderImage from the gsp:

class ArtefactController {

    def createFlow = {
       ............
    }

def renderImage = {

    def ArtefactInstance = Artefact.findById(params.id)
    if(ArtefactInstance?.image) {
        response.setContentLength(ArtefactInstance.image.length)
        response.outputStream.write(ArtefactInstance.image)
    }
    else {
        response.sendError(404)
    }
}

however for the webflow when I try to call renderFlowImage from a gsp:

def renderFlowImage = {
    if(flow.artefactCommand?.image) {
        response.setContentLength(flow.artefactCommand.image.length)
        response.outputStream.write(flow.artefactCommand.image)
    }
    else {
        response.sendError(404)
    }
}

The flow scope in not accessable.

Any suggestions?

Answer 1

I assume you’re hitting the renderFlowImage action in your flow’s view with a second http request via an img tag such as:

<img src="${createLink(action:'renderFlowImage')}" />

This won’t work because, for one thing, you need to pass in a ‘flowExecutionKey’ which grails uses to match a request with a flow.
It is possible to work around this, but you might be better off just rendering the image during the rendering phase of your flow’s next view with a data URI in the img tag. You could do this easily with the rendering plugin, which provides some handy tags (among other things) to render inline images using a data uri.
So in the next flow view, you could replace the existing img tag with a call to one of the rendering plugin’s ‘inline’ tags:

<rendering:inlineJpeg bytes="${artefactCommand.image}" /> 

But be careful – there are some limitations to the data URI approach to be aware of (see http://www.7cynics.com/webdesign/css/css-inline-images-data-uri.html).