我们登陆各种网站都可以看到需要输入验证码，那么这种随机的验证码要如何做出来呢，其实很简单，看完这篇文章你就会了前端的html代码

 <div style="margin-top: 50px;">        <span>验证码：</span><input type="text" name="verifyCode" id="verifyCode" style="width: 75px;height: 25px;"/>        <img id="verifyCodeImg" alt="点击更换" src="/qos/dog/getVerifyCodeImg"            title="点击更换" onclick="change()">    </div>注释：此处的src="/qos/dog/getVerifyCodeImg"   SpringBoot页面展示Thymeleaf的语法

   function change() {        var verifyCode = document.getElementById("verifyCodeImg");        verifyCode.src = "/qos/dog/getVerifyCodeImg?time=" + Math.random(1000);    }/*-*/ /qos/dog/  这里的路径是需要换成自己的哦

代码如下：

package com.paladin.qos.util; import javax.imageio.ImageIO;import java.awt.*;import java.awt.image.BufferedImage;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.util.Random; public class VerifyCodeUtil {     private static final Random random = new Random();    private static final String[] fontNames = {"宋体", "华文楷体", "黑体", "Georgia", "微软雅黑", "楷体_GB2312"};     public static String drawImage(ByteArrayOutputStream output) {        String code = "";        int width = 50;        int height = 25;         //创建图片缓冲区        BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);         Graphics2D g = bi.createGraphics();         //设置背景颜色        g.setBackground(new Color(255, 255, 255));        g.clearRect(0, 0, width, height);         StringBuilder stringBuilder = new StringBuilder();        //这里只画入四个字符        for (int i = 0; i < 4; i++) {            String s = randomChar() + "";      //随机生成字符，因为只有画字符串的方法，没有画字符的方法，所以需要将字符变成字符串再画            stringBuilder.append(s);           //添加到StringBuilder里面            float x = i * 1.0F * width / 4;   //定义字符的x坐标            g.setFont(randomFont());           //设置字体，随机            g.setColor(randomColor());         //设置颜色，随机            g.drawString(s, x, height - 5);        }        code = stringBuilder.toString();//获取验证码字符串         //定义干扰线        //定义干扰线的数量（3-5条）int num = random.nextInt(max)%(max-min+1) + min;        int num = random.nextInt(5) % 3 + 3;        Graphics2D graphics = (Graphics2D) bi.getGraphics();        for (int i = 0; i < num; i++) {            int x1 = random.nextInt(width);            int y1 = random.nextInt(height);            int x2 = random.nextInt(width);            int y2 = random.nextInt(height);            graphics.setColor(randomColor());            graphics.drawLine(x1, y1, x2, y2);        }        // 释放图形上下文        g.dispose();        try {            ImageIO.write(bi, "jpg", output);        } catch (IOException e) {            e.printStackTrace();        }        return code;//为了方便取值，直接返回code，       }     //随机字体    private static Font randomFont() {        int index = random.nextInt(fontNames.length);        String fontName = fontNames[index];        int style = random.nextInt(4);         //随机获取4种字体的样式        int size = random.nextInt(20) % 6 + 15;    //随机获取字体的大小(10-20之间的值)        return new Font(fontName, style, size);    }     //随机颜色    private static Color randomColor() {        int r = random.nextInt(225);        int g = random.nextInt(225);        int b = random.nextInt(225);        return new Color(r, g, b);    }      //随机字符    private static char randomChar() {        //A-Z,a-z,0-9,可剔除一些难辨认的字母与数字        String str = "0123456789ABCdefghiDEFGHIJopPQRVWXYZabcjklSTUmnqrstKLMNOvuwxyz";         return str.charAt(random.nextInt(str.length()));    } }

最后，在controller里面引用

    @RequestMapping("/getVerifyCodeImg")    @ResponseBody    public void getVerifyCodeImg(HttpServletResponse response, HttpSession session) {        ByteArrayOutputStream output = new ByteArrayOutputStream();        String code = VerifyCodeUtil.drawImage(output);        //将验证码文本直接存放到session中        session.setAttribute("verifyCode", code);        try {            ServletOutputStream out = response.getOutputStream();            output.writeTo(out);        } catch (IOException e) {            e.printStackTrace();        }    }

到这里一个随机验证码的小功能就做出来了是不是很简单呢，感兴趣的朋友可以码住文章然后去试一下。