1.pom 文件

<!-- kaptcha验证码 -->
		<dependency>
			<groupId>com.github.penggle</groupId>
			<artifactId>kaptcha</artifactId>
			<version>2.3.2</version>
		</dependency>

2.  Config配置文件

import com.google.code.kaptcha.impl.DefaultKaptcha;
import com.google.code.kaptcha.util.Config;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.util.Properties;

/**
 * @Description:
 * @Param:
 * @return:
 * @Author: fuguowen
 * @date: 2019-08-06 16:22
 * @email: fuguowen@fantaike.ai
 */
@Configuration
public class KaptchaConfig {
    @Bean
    public DefaultKaptcha getDefaultKaptcha(){
        DefaultKaptcha captchaProducer = new DefaultKaptcha();
        Properties properties = new Properties();
        properties.setProperty("kaptcha.border", "yes");
        properties.setProperty("kaptcha.border.color", "105,179,90");
        properties.setProperty("kaptcha.textproducer.font.color", "blue");
        properties.setProperty("kaptcha.image.width", "110");
        properties.setProperty("kaptcha.image.height", "40");
        properties.setProperty("kaptcha.textproducer.font.size", "30");
        properties.setProperty("kaptcha.session.key", "code");
        properties.setProperty("kaptcha.textproducer.char.length", "4");
        properties.setProperty("kaptcha.textproducer.font.names", "宋体,楷体,微软雅黑");
        Config config = new Config(properties);
        captchaProducer.setConfig(config);
        return captchaProducer;

    }
}

3. CodeController

import com.google.code.kaptcha.Constants;
import com.google.code.kaptcha.Producer;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

import javax.imageio.ImageIO;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;

@Controller
public class CodeController {
    @Autowired
    private Producer captchaProducer = null;
    @RequestMapping("/kaptcha")
    public void getKaptchaImage(HttpServletRequest request, HttpServletResponse response) throws Exception {
        HttpSession session = request.getSession();
        response.setDateHeader("Expires", 0);
        response.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");
        response.addHeader("Cache-Control", "post-check=0, pre-check=0");
        response.setHeader("Pragma", "no-cache");
        response.setContentType("image/jpeg");
        //生成验证码
        String capText = captchaProducer.createText();
        System.out.println(capText);
        session.setAttribute(Constants.KAPTCHA_SESSION_KEY, capText);
        //向客户端写出
        BufferedImage bi = captchaProducer.createImage(capText);
        ServletOutputStream out = response.getOutputStream();
        ImageIO.write(bi, "jpg", out);
        boolean jpg = ImageIO.write(bi, "jpg", new File("d:/11.jpg"));
        System.out.println(jpg);
        try {
            out.flush();
        } finally {
            out.close();
        }
    }

}

4. CodeUtil

import javax.servlet.http.HttpServletRequest;

/**
 * 比对验证码的工具类
 */
public class CodeUtil {
    /**
     * 将获取到的前端参数转为string类型
     * @param request
     * @param key
     * @return
     */
    public static String getString(HttpServletRequest request, String key) {
        try {
            String result = request.getParameter(key);
            if(result != null) {
                result = result.trim();
            }
            if("".equals(result)) {
                result = null;
            }
            return result;
        }catch(Exception e) {
            return null;
        }
    }
    /**
     * 验证码校验
     * @param request
     * @return
     */
    public static boolean checkVerifyCode(HttpServletRequest request) {
        //获取生成的验证码
        String verifyCodeExpected = (String) request.getSession().getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);
        //获取用户输入的验证码
        String verifyCodeActual = CodeUtil.getString(request, "verifyCodeActual");
        if(verifyCodeActual == null ||!verifyCodeActual.equals(verifyCodeExpected)) {
            return false;
        }
        return true;
    }
}

5 hello.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>

    <script type="text/javascript">
        function refresh() {
            document.getElementById('captcha_img').src="/kaptcha?"+Math.random();
        }
    </script>
</head>
<body>
<form action="/hello" method="post">
    验证码:  <input type="text" placeholder="请输入验证码" name="verifyCodeActual">
    <div class="item-input">
        <img id="captcha_img" alt="点击更换" title="点击更换"
             onclick="refresh()" src="/kaptcha" />
    </div>
    <input type="submit" value="提交" />
</form>

</body>
</html>