Example of a Spring MVC Controller which Displays a Graph from JFreeChart

GraphController.java

package org.khill.dashboard.controller;

import java.util.Calendar;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;

import java.awt.Color;
import java.awt.Font;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.Map;
import java.util.TimeZone;

import javax.imageio.ImageIO;

import org.jfree.chart.ChartFactory;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.plot.XYPlot;
import org.jfree.chart.renderer.xy.XYItemRenderer;
import org.jfree.chart.renderer.xy.XYLineAndShapeRenderer;
import org.jfree.chart.title.TextTitle;
import org.jfree.data.time.Minute;
import org.jfree.data.time.RegularTimePeriod;
import org.jfree.data.time.Second;
import org.jfree.data.time.TimeSeries;
import org.jfree.data.time.TimeSeriesCollection;
import org.jfree.ui.RectangleInsets;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.servlet.ModelAndView;

/**
 * Example controller showing how to display a graph from JFreeChart
 * 
 * @author khill
 *
 */
@Controller
public class GraphController {

    @Autowired
    private ReportDAO reportDao;

    @RequestMapping("/minuteGraph.htm")
    public ResponseEntity <byte []> getUpdatesByMinuteGraph() {
        HttpStatus responseCode = HttpStatus.OK;
        byte [] image = new byte[0];
        Map <String,Long> updatesByMinute = reportDao.loadUpdateCountsByMinute(15);
        try {
            image = this.getUpdateCountByMinuteGraph(updatesByMinute);
        } catch (Exception e) {
            responseCode = HttpStatus.INTERNAL_SERVER_ERROR;
        }
        return new ResponseEntity<byte[]>(image, responseCode);
    }

    /*
     * Creates a line graph using JFreeChart
     */
    private byte [] getGraphFromDataSet(TimeSeriesCollection dataset, String titleText, String xLabel, String yLabel) throws Exception {
        // create the chart
        JFreeChart chart = ChartFactory.createTimeSeriesChart(
                titleText,  // title
                xLabel,          // x-axis label
                yLabel,          // y-axis label
                dataset,            // data
                true,               // create legend?
                true,               // generate tooltips?
                false               // generate URLs?
            );
        
        TextTitle title = chart.getTitle();
        title.setPaint(new Color(0, 84, 148));
        title.setFont(new Font("Lucida Sans Unicode", Font.BOLD, 12));
        XYPlot plot = (XYPlot) chart.getPlot();
        
        Color fgColor = new Color(46, 110, 158);
        Color bgColor = new Color(228, 232, 234);
        Color gridColor = new Color(128, 128, 128);
        
        chart.getLegend().setItemPaint(fgColor);
        
        plot.setBackgroundPaint(bgColor);
        plot.setDomainGridlinePaint(gridColor);
        plot.setRangeGridlinePaint(gridColor);
        plot.setAxisOffset(new RectangleInsets(5.0, 5.0, 5.0, 5.0));
        plot.setDomainCrosshairVisible(true);
        plot.setRangeCrosshairVisible(true);

        XYItemRenderer r = plot.getRenderer();
        if (r instanceof XYLineAndShapeRenderer) {
            XYLineAndShapeRenderer renderer = (XYLineAndShapeRenderer) r;
            renderer.setBaseItemLabelPaint(fgColor);
            renderer.setSeriesItemLabelPaint(0, fgColor);
            renderer.setBaseFillPaint(fgColor);
            renderer.setBaseOutlinePaint(fgColor);
            renderer.setSeriesPaint(0, fgColor);
            renderer.setBaseShapesVisible(false);
            renderer.setBaseShapesFilled(false);
            renderer.setDrawSeriesLineAsPath(true);
        }
        BufferedImage img = chart.createBufferedImage(600, 300);        
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ImageIO.write(img, "PNG", baos);
        return baos.toByteArray();
        
    }
    
    /**
     * Creates a time series graph for a specific frequency
     * 
     * @param updateCounts      the update data information which forms the basis of the graph
     * @param frequency         the period frequency
     * @return  a chart PNG in byte array form
     * @throws Exception
     */
    private byte [] getTimeSeriesGraph(Map <String,Long> updateCounts, int frequency) throws Exception {
        if(frequency != Calendar.MINUTE && frequency != Calendar.SECOND) {
            throw new IllegalArgumentException("Unsupported time series frequency specified - must be minutes or seconds");
        }
        // build the dataset
        TimeSeries ts = new TimeSeries("UpdateCount");
        RegularTimePeriod p = null;
        Date d = null;
        Date start = null;
        Date end = null;
        DateFormat f = null;
        if(frequency == Calendar.MINUTE) {
            f = new SimpleDateFormat("MM-dd-yyyy HH:mm");
        }
        if(frequency == Calendar.SECOND) {
            f = new SimpleDateFormat("MM-dd-yyyy HH:mm:ss");
        }
        for(String s : updateCounts.keySet()) {
            d = f.parse(s);
            if(start == null || d.getTime() < start.getTime()) {
                start = d;
            }
            if(end == null || d.getTime() > end.getTime()) {
                end = d;
            }
            if(frequency == Calendar.MINUTE) {
                p = RegularTimePeriod.createInstance(Minute.class, d, TimeZone.getDefault());
                ts.add(p, updateCounts.get(s));
            }
            if(frequency == Calendar.SECOND) {
                p = RegularTimePeriod.createInstance(Second.class, d, TimeZone.getDefault());
                ts.add(p, updateCounts.get(s));
            }
        }
        String chartTitle = null;
        String xTitle = null;
        if(frequency == Calendar.MINUTE) {
            chartTitle = "Updates per Minute";
            if(end != null && start != null) {
                long minuteDelta = (end.getTime() - start.getTime()) / (60 * 1000);
                chartTitle = chartTitle + " (Last " + minuteDelta + " Minutes)";
                xTitle = "minutes";
            }
        }
        if(frequency == Calendar.SECOND) {
            chartTitle = "Updates per Second";
            if(end != null && start != null) {
                long delta = (end.getTime() - start.getTime()) / (1000);
                chartTitle = chartTitle + " (Last " + delta + " Seconds)";
                xTitle = "seconds";
            }
        }
        TimeSeriesCollection dataset = new TimeSeriesCollection();
        dataset.addSeries(ts);
        return this.getGraphFromDataSet(dataset, chartTitle, xTitle, "updates");        
    }
}