转载自：http://www.xrss.cn/Dev/JAVA/200792816836.Html
实现非常简单，例子主要有3个类，ImageContainer.java 在内存中保存动态走势图，ImageServlet.java 输出图片servlet，RandomValueThread.java模拟随机数据的线程。

为了要生成gif 图片 ，请先在http://www.fmsware.com/stuff/gif.zip 下载处理GIF图片的代码，解压之后可以发现有AnimatedGifEncoder.java, GifDecoder.java, ... 其中AnimatedGifEncoder.是用来生成GIF文件的

Gif图片比Jpeg 要小的多，另外动态走势图保存在内存中，不用生成图片文件的。

准备一张背景图片400×200大小，如下

ImageContainer.java

package com.web;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.LinkedList;
import java.util.List;
import javax.imageio.ImageIO;

public class ImageContainer {

    public final static int MAX_LIST_SIZE = 100;

    public final static int DEFAULT_WIDTH = 400;

    public final static int DEFAULT_HEIGHT = 200;

    public final static int DOT_WIDTH = 4;

    public final static int DOT_HEIGHT = 2;

    public final static String BACKGROUND_IMAGE = "/bg.gif";

    private LinkedList<Integer> valueList = new LinkedList<Integer>();

    private Image image = null;

    private void loadImageFile() {
        File file = new File(this.getClass().getResource(BACKGROUND_IMAGE)
                .getFile());
        try {
            image = ImageIO.read(file);
        } catch (IOException e) {
            System.err.println("Can not load backgroud, reason:"
                    + e.getMessage());
        }
    }

    private ImageContainer() {
    }

    private static ImageContainer intance = new ImageContainer();

    public static ImageContainer getInstance() {
        return intance;
    }

    public synchronized List getList() {
        return valueList;
    }

    public synchronized void pushValue(Integer value) {
        if (valueList.size() >= MAX_LIST_SIZE) {
            valueList.poll();
        }
        valueList.offer(value);
    }

    public BufferedImage draw() {
        BufferedImage tag = new BufferedImage(DEFAULT_WIDTH, DEFAULT_HEIGHT,
                BufferedImage.TYPE_INT_RGB);
        if (image == null) {
            loadImageFile();
        }
        if (image != null) {
            int width = image.getWidth(null);
            int height = image.getHeight(null);
            tag.getGraphics().drawImage(image, 0, 0, width, height, null);
        }

        Graphics g = tag.getGraphics();
        g.setColor(Color.GREEN);
        List valueList = this.getList();
        int x1 = 0, y1 = 0, x2 = 0, y2 = 0;
        int size = valueList.size();
        int offset = (MAX_LIST_SIZE - size) * DOT_WIDTH;
        x1 = offset;
        y1 = DEFAULT_HEIGHT-0;
        for (int i = 0; i < size; i++) {
            x2 = offset + i * DOT_WIDTH;
            y2 = DEFAULT_HEIGHT-(Integer) valueList.get(i) * DOT_HEIGHT;
            g.drawLine(x1, y1, x2, y2);
            System.out.printf("drawLine[%d,%d,%d,%d]", x1, y1, x2, y2);
            x1 = x2;
            y1 = y2;
        }
        System.out.println();
        return tag;
    }

}

RandomValueThread.java

package com.web;

import java.util.Random;

public class RandomValueThread extends Thread {

    private boolean isRunning = false;

    public synchronized boolean isRunning() {
        return isRunning;
    }

    public synchronized void setRunning(boolean isRunning) {
        this.isRunning = isRunning;
    }

    @Override
    public synchronized void start() {
        isRunning = true;
        super.start();
    }

    @Override
    public void run() {
        int v;
        Random randomp = new Random();
        while (isRunning) {
            v = randomp.nextInt(100);
            System.out.println("Put random value=" + v);
            ImageContainer.getInstance().pushValue(v);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
            }
        }
    }
}

ImageServlet.java

package com.web.servlet;

import giftool.AnimatedGifEncoder;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.web.ImageContainer;
import com.web.RandomValueThread;

public class ImageServlet extends HttpServlet {

    private static final String GIF = "image/gif";

    private static final String JPG = "image/jpeg";

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType(GIF);
        BufferedImage image = ImageContainer.getInstance().draw();
        OutputStream out = response.getOutputStream();
        // JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
        // encoder.encode(image);
        AnimatedGifEncoder encoder = new AnimatedGifEncoder();
        encoder.setRepeat(0);
        encoder.start(out);
        encoder.addFrame(image);
        encoder.finish();
       
        out.close();
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }

    public void init() throws ServletException {
        // Start random value thread
        RandomValueThread thread = new RandomValueThread();
        thread.setDaemon(true);
        thread.start();
    }

}

 web.xml 加入

  <servlet>
    <servlet-name>ImageServlet</servlet-name>
    <servlet-class>com.web.servlet.ImageServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>ImageServlet</servlet-name>
    <url-pattern>/ImageServlet</url-pattern>
  </servlet-mapping>

 

demo.htm

<html>
    <body>
        Memory Copy Buffer Image
        <br>

        <img src="" id="viewImg" />
    </body>
</html>
<script language="javascript">...
function refreshImage() ...{
 document.getElementById("viewImg").src="ImageServlet?"+Math.random();
 setTimeout(refreshImage,1000);
}

setTimeout(refreshImage,1000);
</script>
 

最终演示效果图: