Java使用Servlet生成验证码图片_Java教程

Java使用Servlet生成验证码图片

2021-12-01 13:15IT教育-汤小洋 Java教程

这篇文章主要为大家详细介绍了Java使用Servlet生成验证码图片，文中示例代码介绍的非常详细，具有一定的参考价值，感兴趣的小伙伴们可以参考一下

本文实例为大家分享了Java使用Servlet生成验证码图片的具体代码，供大家参考，具体内容如下

一、实现思路

1、使用BufferedImage用于在内存中存储生成的验证码图片
2、使用Graphics来进行验证码图片的绘制，并将绘制在图片上的验证码存放到session中用于后续验证
3、最后通过ImageIO将生成的图片进行输出
4、页面通过访问servlet来获取并展示验证码
5、在后台获取页面提交的验证码，然后和存放在session中的验证码进行比对，进行校验

二、生成验证码

生成验证码的servlet，如下所示：

				?

									@WebServlet("/code")

									public class CodeController {

									    @Override

									    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

									        request.setCharacterEncoding("utf-8");

									        BufferedImage bfi = new BufferedImage(80,25,BufferedImage.TYPE_INT_RGB);

									        Graphics g = bfi.getGraphics();

									        g.fillRect(0, 0, 80, 25);

									        //验证码字符范围

									        char[] ch = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789".toCharArray();

									        Random r = new Random();

									        int index;

									        StringBuffer sb = new StringBuffer(); //保存字符串

									        for(int i=0; i<4; i++){

									            index = r.nextInt(ch.length);

									            g.setColor(new Color(r.nextInt(255),r.nextInt(255),r.nextInt(255)));

									            Font font = new Font("宋体", 30, 20);

									            g.setFont(font);

									            g.drawString(ch[index]+"", (i*20)+2, 23);

									            sb.append(ch[index]);

									        }

									        // 添加噪点

									        int area = (int) (0.02 * 80 * 25);

									        for(int i=0; i<area; ++i){

									            int x = (int)(Math.random() * 80);

									            int y = (int)(Math.random() * 25);

									            bfi.setRGB(x, y, (int) (Math.random() * 255));

									        }

									        //设置验证码中的干扰线

									        for (int i = 0; i < 4; i++) {

									            //随机获取干扰线的起点和终点

									            int xstart = (int)(Math.random() * 80);

									            int ystart = (int)(Math.random() * 25);

									            int xend = (int)(Math.random() * 80);

									            int yend = (int)(Math.random() * 25);

									            g.setColor(interLine(1, 255));

									            g.drawLine(xstart, ystart, xend, yend);

									        }

									        HttpSession session = request.getSession();  //保存到session

									        session.setAttribute("verificationCode", sb.toString());

									        ImageIO.write(bfi, "JPG", response.getOutputStream());  //写到输出流

									    }

									    private Color interLine(int Low, int High){

									        if(Low > 255)

									            Low = 255;

									        if(High > 255)

									            High = 255;

									        if(Low < 0)

									            Low = 0;

									        if(High < 0)

									            High = 0;

									        int interval = High - Low;

									        int r = Low + (int)(Math.random() * interval);

									        int g = Low + (int)(Math.random() * interval);

									        int b = Low + (int)(Math.random() * interval);

									        return new Color(r, g, b);

									    }

									}