使用java编写验证码-蒲公英云

使用java编写验证码

package com.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;
/** * 验证码 * 猜想：生成的验证码，到时候可以跟输入的账号一起存到缓存redis中，key工号 value验证码 设置过期时间 * 用户输入验证码点击确定之后，获取redis中的数据进行比对，如果获取不到缓存说明已经过期，页面刷新，重新插入一条验证码到缓存中。 * 进行验证正确就允许登陆 */
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");
        BufferedImage bufferedImage = new BufferedImage(90,30,BufferedImage.TYPE_INT_RGB);
        Graphics2D graphics = (Graphics2D)bufferedImage.getGraphics();
        //填充颜色
        graphics.setColor(Color.BLUE);
        //画一个边框
        graphics.fillRect(0,0,90,30);
        //给图片写数据
        graphics.setColor(Color.yellow);
        graphics.setFont(new Font(null,Font.BOLD,20));
        graphics.drawString(getRandomNum(),10,20);
        //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());
    }
    /** * 计算随机数 * @return */
    private String getRandomNum(){ 
        Random random = new Random();
        String i1 = random.nextInt(999999) + "";
        StringBuffer stringBuffer = new StringBuffer();
        for (int i = 0; i < 6 - i1.length() ; i++) { 
            stringBuffer.append("0");
        }
        i1 = stringBuffer.toString() + i1;
        return i1;
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
        doGet(req, resp);
    }
}