效果
实现思路
验证码图片的url由后端的一个Controller生成，前端请求这个Controller接口的时候根据当前时间生成一个uuid，并把这个uuid在前端使用localStorage缓存起来，下一次还是从缓存中获取。
Controller生成验证码之后，把前端传过来的uuid通过redis缓存起来，这里分两次缓存
- 缓存uuid
- 以uuid为key，缓存验证码
这样，当点击登录按钮将数据提交到后台登录接口时，会从redis中获取uuid，然后通过这个uuid去获取验证码，和前端用户输入的验证码进行比较。
简单验证码
生成随机字符（如数字、字母）的字符串，并将这些字符绘制到一张图片上，最后输出这张图片。
java">import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Random; public class CaptchaGenerator { private static final int WIDTH = 100; private static final int HEIGHT = 40; private static final Random RANDOM = new Random(); public static void main(String[] args) { // 生成验证码文本 String captchaText = generateCaptchaText(6); // 生成验证码图片 File outputFile = new File("captcha.png"); generateCaptchaImage(captchaText, outputFile); System.out.println("Captcha generated: " + captchaText); } private static String generateCaptchaText(int length) { StringBuilder sb = new StringBuilder(length); for (int i = 0; i < length; i++) { // 随机选择字符类型 int type = RANDOM.nextInt(3); if (type == 0) { // 数字 sb.append(RANDOM.nextInt(10)); } else if (type == 1) { // 小写字母 sb.append((char) ('a' + RANDOM.nextInt(26))); } else { // 大写字母 sb.append((char) ('A' + RANDOM.nextInt(26))); } } return sb.toString(); } private static void generateCaptchaImage(String captchaText, File outputFile) { BufferedImage bufferedImage = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB); Graphics2D g2d = bufferedImage.createGraphics(); // 设置背景色 g2d.setColor(Color.WHITE); g2d.fillRect(0, 0, WIDTH, HEIGHT); // 设置字体 Font font = new Font("Arial", Font.BOLD, 24); g2d.setFont(font); // 绘制验证码文本 g2d.setColor(Color.BLACK); FontMetrics fontMetrics = g2d.getFontMetrics(); int x = (WIDTH - fontMetrics.stringWidth(captchaText)) / 2; int y = ((HEIGHT - fontMetrics.getHeight()) / 2) + fontMetrics.getAscent(); g2d.drawString(captchaText, x, y); // 释放资源 g2d.dispose(); // 输出图片 try { ImageIO.write(bufferedImage, "png", outputFile); } catch (IOException e) { e.printStackTrace(); } }
}
工具包
- Hutool：是一个多功能的工具包，其中有验证码的功能hutool-captcha
- easy-captcha：专注验证码
Hutool demo
1、添加依赖
<dependency><groupId>cn.hutool</groupId><artifactId>hutool-all</artifactId><version>5.7.16</version>
</dependency>
2、写一个控制器
java">package com.zhangyu.controller;import cn.hutool.captcha.CaptchaUtil;
import cn.hutool.captcha.LineCaptcha;
import cn.hutool.json.JSONObject;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;@RestController
public class CaptchaController {@GetMapping("/captcha")public Map captcha(HttpServletRequest request, HttpServletResponse response) throws IOException {// 生成验证码图片 LineCaptcha lineCaptcha = CaptchaUtil.createLineCaptcha(200, 100, 4, 4);// 获取验证码图片上的文字String captchaText = lineCaptcha.getCode();// 将验证码文字放入session，键名为 CAPTCHA_KEYrequest.getSession().setAttribute("CAPTCHA_KEY", captchaText);System.out.println("文字是" + captchaText);// 输出图片 BufferedImage image = lineCaptcha.getImage();// 图片转base64String base = ImageToBase64.convertImageToBase64(image);System.out.println("base文字是" + base);// 组装数据Map resultMap = new HashMap();resultMap.put("code", captchaText);resultMap.put("img", "data:image/png;base64," + base);return resultMap;}@PostMapping("/submit")public String submit(HttpServletRequest request, @RequestBody JSONObject jsonObject) {String captcha = jsonObject.getStr("captcha");String sessionCaptcha = (String) request.getSession().getAttribute("CAPTCHA_KEY");if (captcha.equalsIgnoreCase(sessionCaptcha)) {return "验证码正确！";} else {return "验证码错误，请重试！";}}
}
java">package com.zhangyu.controller;import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.util.Base64;
import java.io.IOException;public class ImageToBase64 {public static String convertImageToBase64(BufferedImage image) throws IOException {ByteArrayOutputStream baos = new ByteArrayOutputStream();ImageIO.write(image, "png", baos); // 可以改为需要的图片格式，如"jpg"byte[] imageBytes = baos.toByteArray();return Base64.getEncoder().encodeToString(imageBytes);}
}
3、前端测试
这里我用vue写了一个简单的demo
<template><div class="home"><img :src="imgUrl" @click="getCaptchaImg()" alt="captcha" title="点击刷新"><input type="text" name="captcha" placeholder="输入验证码" v-model="text"><button type="submit" @click="submitCaptcha()">提交</button></div>
</template><script>
import baseApi from '@/api/base'
export default {name: 'HomeView',data () {return {imgUrl: '',text: ''}},methods: {async getCaptchaImg() {const res = await baseApi.getCaptchaImg()this.imgUrl = res.img},async submitCaptcha() {const params = {captcha: this.text,}const res = await baseApi.submitCaptcha(params)}},async mounted () {this.getCaptchaImg()}
}
</script>import ajax from '@/libs/ajax'const baseApi = {getCaptchaImg: () => ajax.request({url: '/captcha',method: 'get'}),submitCaptcha: (data) => ajax.request({url: '/submit',method: 'post',data})
}
export default baseApi
devServer: {port: 9001,open: false,// 配置跨域请求头，解决开发环境的跨域问题headers: {'Access-Control-Allow-Origin': '*',},proxy: 'http://192.168.18.21:9090/'
},
4、效果
总结
这里只是用Hutool工具包做了一个demo，easy-captcha我就不展示了也差不多。
真实的场景是返回给前端base64图片和一个uuid，并不是我这里展示的图片文字，然后提交的时候前端把uuid和输入内容传递给后端，由于我这里只是demo所以没有牵扯uuid
