在jsp中使用servlet的JFree图表答案

【问题标题】：JFree chart by using servlet in jsp在jsp中使用servlet的JFree图表
【发布时间】：2011-07-24 09:44:13
【问题描述】：

如何使用 Servlet 和渲染图像绘制折线图？我写了一个servlet并创建了一个图表。但我不知道如何在我的jsp页面上显示它。

我的 servlet 代码：

public class GraphGen extends HttpServlet {

    public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        genGraph(req, resp);
    }

    public void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        genGraph(req, resp);
    }

    @SuppressWarnings("deprecation")
    public void genGraph(HttpServletRequest req, HttpServletResponse resp) {

        try {
            OutputStream out = resp.getOutputStream();

            // Create a simple Bar chart
            System.out.println("Setting dataset values");

            DefaultCategoryDataset dataset = new DefaultCategoryDataset();
            dataset.setValue(30, "Girls","SCIENCE CLASS");
            dataset.setValue(30,  "Boys","SCIENCE CLASS");
            dataset.setValue(10,  "Girls","ECONOMICS CLASS");
            dataset.setValue(50, "Boys","ECONOMICS CLASS");
            dataset.setValue(5, "Girls","LANGUAGE CLASS");
            dataset.setValue(55, "Boys","LANGUAGE CLASS");

            JFreeChart chart = ChartFactory.createBarChart3D(
                "Comparison between Girls and Boys in Science," + "Economics and Language classes",
                "Students Comparisons", "No of Students",
                dataset,
                PlotOrientation.VERTICAL,
                true,
                true,
                false);

            chart.setBackgroundPaint(Color.white);

            // Set the background colour of the chart
            chart.getTitle().setPaint(Color.blue);

            // Adjust the colour of the title
            CategoryPlot plot = chart.getCategoryPlot();

            // Get the Plot object for a bar graph
            plot.setBackgroundPaint(Color.white);
            plot.setRangeGridlinePaint(Color.red);

            CategoryItemRenderer renderer = plot.getRenderer();
            renderer.setSeriesPaint(0, Color.red);
            renderer.setSeriesPaint(1, Color.green);
            renderer.setItemURLGenerator(
                new StandardCategoryURLGenerator(
                    "index1.html",
                    "series",
                    "section"));
            renderer.setToolTipGenerator(new StandardCategoryToolTipGenerator());

            resp.setContentType("image/png");

            ChartUtilities.writeChartAsPNG(out, chart, 625, 500);

        } catch (Exception e) {
            System.err.println("Problem occurred creating chart." + e.getMessage());
        }
    }

【问题讨论】：

您是否已经询问过 Google 博士，例如stackoverflow.com/questions/1255717/…?
谢谢，请问您遇到什么问题，到底是什么不行？
如何在jsp页面上显示这个图片？
你必须在你的 JSP 中包含一个<img src="path_to_your_servlet"/> 链接。请记住，在您的情况下，servlet 是图像。
@home 的建议是正确的。您需要使用<img/> 标记链接到servlet。我鼓励您提供比“它没有用”更有用的反馈。

标签： jsp servlets jfreechart

【解决方案1】：

chart.setBackgroundPaint(Color.white);

            // Set the background colour of the chart
            chart.getTitle().setPaint(Color.blue);

            // Adjust the colour of the title
            CategoryPlot plot = chart.getCategoryPlot();

            // Get the Plot object for a bar graph
            plot.setBackgroundPaint(Color.white);
            plot.setRangeGridlinePaint(Color.red);

            CategoryItemRenderer renderer = plot.getRenderer();
            renderer.setSeriesPaint(0, Color.red);
            renderer.setSeriesPaint(1, Color.green);
            renderer.setItemURLGenerator(
                new StandardCategoryURLGenerator(
                    "index1.html",
                    "series",
                    "section"));
            renderer.setToolTipGenerator(new StandardCategoryToolTipGenerator());

            resp.setContentType("image/png");

            ChartUtilities.writeChartAsPNG(out, chart, 625, 500);

......代替上面的代码，只需使用这个代码，这更容易......

JFreeChart chart = ChartFactory.createBarChart3D(
                "Comparison between Girls and Boys in Science," + "Economics and Language classes",
                "Students Comparisons", "No of Students",
                dataset,
                PlotOrientation.VERTICAL,
                true,
                true,
                false);


            try {

                final ChartRenderingInfo info = new ChartRenderingInfo(new StandardEntityCollection());
                final File file1 = new File(getServletContext().getRealPath(".") + "/images/piechart/lineChart.png");

                ChartUtilities.saveChartAsPNG(file1, chart, 600, 400, info);
            } catch (Exception e) {
                System.out.println(e);

            }

......在jsp页面中使用这个代码......

<div>
    <img src="path/images/piechart/lineChart.png"
         width="600" height="400" border="0" usemap="#chart" />
 </div>

【讨论】：