生成随机验证码

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.BufferedInputStream;
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 g = (Graphics2D) bufferedImage.getGraphics();//笔
//设置图片的背景颜色
g.setColor(Color.white);
g.fillRect(0,0,80,20);
//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方式打开
resp.setContentType("image/jpeg");
//网站有缓存,不让浏览器缓存
resp.setDateHeader("exprirs",-1);
resp.setHeader("Cache-Control","no-cache");
resp.setHeader("Pragma","no-cache");
//把图片写给浏览器
boolean write = ImageIO.write(bufferedImage, "jpg",resp.getOutputStream());
}

//生成随机数
private String makeNum(){
Random random = new Random();
String num = random.nextInt(9999999) + "";
StringBuffer stringBuffer = new StringBuffer();

for (int i = 0; i <7-num.length() ; i++) {
stringBuffer.append("0");
}
num = stringBuffer.toString() + num;
return num;
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
posted @ 2021-10-21 22:46  吴大叔  阅读(36)  评论(0编辑  收藏  举报