JSPs usually generate HTML, so you will have to make do with what HTML can do. That would either be embedded SVG (which severely limits your audience, as SVG is not widely supported by current browsers) or an embedded image.
Libraries like JFreeChart and the cewolf JSP tag library based on it (links can be found here) make it very easy to do this. Why don't you want to use those libraries? You'd just be duplicating work already done.