java实现登录页面的验证码功能

落日映苍穹つ 2022-06-07 03:16 192阅读 0赞

我们访问电商网站，登录账号时。都需要验证码的输入。那么在java中，我们是如何实现验证码的呢？这里，我用servelet做个demo。

**代码清单：**

package com.test;
    
    import java.awt.Color;
    import java.awt.Font;
    import java.awt.Graphics;
    import java.awt.image.BufferedImage;
    import java.io.IOException;
    import java.util.Random;
    
    import javax.imageio.ImageIO;
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    /** * Servlet implementation class ValidateCodeServle */
    @WebServlet("/ValidateCodeServle")
    public class ValidateCodeServle extends HttpServlet { 
        private static final long serialVersionUID = 1L;
    
        /** * @see HttpServlet#HttpServlet() */
        public ValidateCodeServle() {
            super();
            // TODO Auto-generated constructor stub
        }
    
        /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            // TODO Auto-generated method stub
            doPost(request, response);
        }
    
        /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            // 响应头信息
            response.setHeader("Pragma", "No-Cache");
            response.setHeader("Cache-Control", "no-cache");
            response.setDateHeader("Expries", 0);
    
            // 随机数生成类
            Random random = new Random();
    
            // 定义验证码的位数
            int size = 5;
    
            // 定义变量保存生成的验证码
            String vCode = "";
            char c;
            // 产生验证码
            for (int i = 0; i < size; i++) {
                // 产生一个26以内的随机整数
                int number = random.nextInt(26);
                // 如果生成的是偶数，则随机生成一个数字
                if (number % 2 == 0) {
                    c = (char) ('0' + (char) ((int) (Math.random() * 10)));
                    // 如果生成的是奇数，则随机生成一个字母
                } else {
                    c = (char) ((char) ((int) (Math.random() * 26)) + 'A');
                }
                vCode = vCode + c;
            }
    
            // 保存生成的5位验证码
            request.getSession().setAttribute("vCode", vCode);
    
            // 验证码图片的生成
            // 定义图片的宽度和高度
            int width = (int) Math.ceil(size * 20);
            int height = 30;
            BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
            // 获取图片的上下文
            Graphics gr = image.getGraphics();
            // 设定图片背景颜色
            gr.setColor(Color.WHITE);
            gr.fillRect(0, 0, width, height);
            // 设定图片边框
            gr.setColor(Color.GRAY);
            gr.drawRect(0, 0, width - 1, height - 1);
            // 画十条干扰线
            for (int i = 0; i < 5; i++) {
                int x1 = random.nextInt(width);
                int y1 = random.nextInt(height);
                int x2 = random.nextInt(width);
                int y2 = random.nextInt(height);
                gr.setColor(randomColor());
                gr.drawLine(x1, y1, x2, y2);
            }
            // 设置字体，画验证码
            gr.setColor(randomColor());
            gr.setFont(randomFont());
            gr.drawString(vCode, 10, 22);
            // 图像生效
            gr.dispose();
            // 输出到页面
            ImageIO.write(image, "JPEG", response.getOutputStream());
    
        }
    
        // 生成随机的颜色
        private Color randomColor() {
            int red = r.nextInt(150);
            int green = r.nextInt(150);
            int blue = r.nextInt(150);
            return new Color(red, green, blue);
        }
    
        private String[] fontNames = { "宋体", "华文楷体", "黑体", "微软雅黑", "楷体_GB2312" };
        private Random r = new Random();
    
        // 生成随机的字体
        private Font randomFont() {
            int index = r.nextInt(fontNames.length);
            String fontName = fontNames[index];// 生成随机的字体名称
            int style = r.nextInt(4);
            int size = r.nextInt(3) + 24; // 生成随机字号, 24 ~ 28
            return new Font(fontName, style, size);
        }
    
    
    }

**测试：**  
![这里写图片描述][SouthEast]

![这里写图片描述][SouthEast 1]

[SouthEast]: /images/20220607/61b5728823514cbaa9697dcd930f56ac.png
[SouthEast 1]: /images/20220607/689432502f5c450aacdb7d9b1f4f43ed.png