jsp做柱状图

<dependency>
    <groupId>org.jfree</groupId>
    <artifactId>jfreechart</artifactId>
    <version>1.5.0</version>
</dependency>

import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartUtils;
import org.jfree.chart.JFreeChart;
import org.jfree.data.category.DefaultCategoryDataset;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class ChartServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        DefaultCategoryDataset dataset = new DefaultCategoryDataset();
        dataset.addValue(15, "Series1", "Category1");
        dataset.addValue(25, "Series1", "Category2");
        dataset.addValue(18, "Series1", "Category3");

        JFreeChart chart = ChartFactory.createBarChart("Sample Bar Chart", "Category", "Value", dataset);

        response.setContentType("image/png");
        ChartUtils.writeChartAsPNG(response.getOutputStream(), chart, 500, 300);
    }
}

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Bar Chart Example</title>
</head>
<body>
    <h2>Bar Chart Example</h2>
    <img src="ChartServlet" alt="Bar Chart"/>
</body>
</html>