Zingchart call getimagedata api via java

Question

I try to export zingchart image to get it in base64 object in java.

I want to use the getimageapi like this in js :

function exportImgChart(idChart) {
zingchart.exec('idChart', 'getimagedata', {
    filetype: 'png',
    callback : function(imagedata) {
        console.log(imagedata);
        document.getElementById('output_image').src = imagedata;
    }
});}

But I don't know how to call it from java code ? I put my js function like this :

    public void getImageChart(AjaxRequestTarget target, String idChart) {

    String js = MessageFormat.format("exportImgChart({0});", //
            StringUtils.wrap(this.getMarkupId(), "'") //
            );

    target.appendJavaScript(js);
    
    //how to get image base 64 here ?

}

My java framework is Wicket

Thanks for your help !

Jeff

Answer 1

getImageChart(AjaxRequestTarget, String) is called because of some Ajax call made from the browser to the server.

Then at the server-side you construct a String that will be sent to the browser with the response. target.appendJavaScript(js); doesn't send it immediately. It just says "'js' will be part of the response" but the response is flushed to the browser once getImageChart() and few more methods are fully executed.

You cannot have the base64 encoded image right after target.appendJavaScript(js). To get the base64 data you need to make a new Ajax call to the server in your JavaScript function exportImgChart(). This new Ajax call will most probably call new callback method, e.g. onBase64Image() or whatever you name it.

For more information see this answer: https://stackoverflow.com/a/42612027/497381