利用JFreeChart在browser中绘图(Servlet)_browserservlet-优快云博客

Step 1 :
HTML:
MyHtml.html include a button, this button submit a request "draw" to "ChartServlet" servlet, "ChartServlet" will give a response.

MyHtml.html is like this:

 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>MyHtml.html</title>
    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="this is my page">
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
    
    <!--<link rel="stylesheet" type="text/css" href="./styles.css">-->
  </head>
  
  <body><h3>Draw a Chat !</h3><br>
    <form action="draw.do" method="get" name ="myform">
    <input type="submit" name="b1" value="draw"></input>
    </form>
  </body>
</html>

Step 2:

modifY web.xml

 <?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" 
    xmlns="http://java.sun.com/xml/ns/j2ee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
    http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>ChartServlet</servlet-name>
    <servlet-class>ChartServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>ChartServlet</servlet-name>
    <url-pattern>/draw.do</url-pattern>
  </servlet-mapping>
</web-app>

Step 3:

ChartServlet recieves the request, then response it with the type "image/png" like this

 import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartUtilities;
import org.jfree.chart.JFreeChart;
import org.jfree.data.general.DefaultPieDataset;
import com.lowagie.text.pdf.codec.Base64.OutputStream;
public class ChartServlet extends HttpServlet {
    /**
     * Constructor of the object.
     */
    public ChartServlet() {
        super();
    }
    /**
     * Destruction of the servlet. <br>
     */
    public void destroy() {
        super.destroy(); // Just puts "destroy" string in log 
        // Put your code here 
    }
    /**
     * The doGet method of the servlet. <br>
     *
     * This method is called when a form has its tag value method equals to get.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        ServletOutputStream out = response.getOutputStream(); 
//       createadataset... 
        DefaultPieDataset dataset = new DefaultPieDataset();
        dataset.setValue("Category1", 43.2);
        dataset.setValue("Category2", 27.9);
        dataset.setValue("Category3", 79.5);
        // createachart... 
        JFreeChart chart = ChartFactory.createPieChart("SamplePieChart",
                dataset, true,// legend? 
                true,// tooltips? 
                false// URLs? 
                );
        response.setContentType("image/png");
        ChartUtilities.writeChartAsPNG(out,chart,400,300);
        out.close();
    }
    /**
     * Initialization of the servlet. <br>
     *
     * @throws ServletException if an error occure
     */
    public void init() throws ServletException {
        // Put your code here 
    }
}

This servlet just do one simple thing, when request whose name is "draw" comes, the servlet will draw a chart(with JFreeChart support), the result is a image file as png, then, it adds this file to the response stream., which will output by the browser

Here we go!

Contact me! Tony80plus@gmail.com