Sometimes we get asked for the Java code to create a simple chart. Once you’ve done it a few times, you forget it can be useful to have this code the first time. So here’s a step-through for building a basic chart that can be included in a servlet, for instance, and returned to a JSP.
First, create the chart object, and a String to hold the HTML that will be returned:
NFXYchart chart = null;
String chartHtml = null;
Then use our static method to create a chart from a CDL template:
chart = (NFXYchart) NFGraph.getGraphFromTemplate(getDefaultXYChart());
Finally, add a LineSeries (that holds datasets) and a LineSet:
NFLineSeries ls = chart.getLineSeries();
NFLineSet set = (NFLineSet)ls.elementAt(0);
Now it’s time to add data. Here we add four x,y data points to the dataset:
Done-zo! Now we add the dataset to the series, and the series to the chart:
To generate the HTML for a web page, we provide another static method to make things easy:
chartHtml = NFServletUtil.getPage(request, chart, new NFRasterPageParams());
where request is the HttpServletRequest. That’s it! Set a page attribute to the chartHtml and you’re done. We provide the full servlet source here, and a simple JSP here.