ImageServlet：
package com.allen.servlet;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
public class ImageServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//如何让浏览器3秒自动刷新一次；
resp.setHeader("refresh", "3");
//在内存中创建一个图片
BufferedImage image = new BufferedImage(100, 20, BufferedImage.TYPE_INT_RGB);
//得到图片
Graphics2D g = (Graphics2D) image.getGraphics(); //笔
//设置图片背景颜色
g.setColor(Color.white);
g.fillRect(0, 0, 100, 20);
//给图片写数据
g.setColor(Color.BLUE);
g.setFont(new Font(null, Font.BOLD, 20));
g.drawString(makeNum(), 0, 20);
//告诉浏览器，这个请求用图片的打开方式
resp.setContentType("image/jpeg");
//网站存在缓存，不让浏览器缓存
resp.setDateHeader("expires", -1);
resp.setHeader("Cache-Control", "no-cache");
resp.setHeader("Pragma", "no-cache");
//把图片写给浏览器
ImageIO.write(image, "jpg", resp.getOutputStream());
}
//生成随机数
private String makeNum(){
Random random = new Random();
String num = random.nextInt(9999999) + "";
StringBuffer sb = new StringBuffer();
for(int i = 0; i < 7 - num.length(); i++){
sb.append("0");
}
num = sb.toString() + num;
return num;
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doGet(req, resp);
}
}web.xml
<servlet> <servlet-name>ImageServlet</servlet-name> <servlet-class>com.allen.servlet.ImageServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>ImageServlet</servlet-name> <url-pattern>/img</url-pattern> </servlet-mapping>
测试：
