一、创建ImageServlet类
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 bufferedImage = new BufferedImage(80, 20,BufferedImage.TYPE_INT_RGB);
//得到图片
Graphics2D graphics = (Graphics2D)bufferedImage.getGraphics();//笔
//设置图片的背景颜色
graphics.setColor(Color.white);
graphics.fillRect(0,0,80,20);
//给图片写数据
graphics.setColor(Color.BLUE);
graphics.setFont(new Font(null,Font.BOLD,20));
graphics.drawString(makeNum(),0,20);
//告诉浏览器这个请求用图片的方式打开
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(bufferedImage, "jpg",resp.getOutputStream());
}
//生成随机数
private String makeNum(){
Random random = new Random();
String num=random.nextInt(99999999)+"";
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 {
doGet(req, resp);
}
}
二、注册Servlet(在web.xml中)
<servlet>
<servlet-name>image</servlet-name>
<servlet-class>com.huang.servlet.ImageServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>image</servlet-name>
<url-pattern>/image</url-pattern>
</servlet-mapping>
三、运行结果