I am using HighChart in my application. I want to export chart image on a button click like http://jsfiddle.net/hfrntt/fXHB5/1896/. but i want to save image in a predefined fold
This is going to involve much more than simply using highcharts. You are going to have to use some sort of wrapper that will actually render the chart/page on the server-side and then essentially output it as an image. The following are links taken from a post on the highcharts website.
GWT Highcharts wrapper
Highcharts-server-side-export (with Rhino/Batik)