一、导入依赖

<!-- 验证码 -->
        <dependency>
            <groupId>com.github.penggle</groupId>
            <artifactId>kaptcha</artifactId>
            <version>2.3.2</version>
            <exclusions>
                <exclusion>
                    <artifactId>javax.servlet-api</artifactId>
                    <groupId>javax.servlet</groupId>
                </exclusion>
            </exclusions>
        </dependency>

或

<dependency>
    <groupId>com.google.code.kaptcha</groupId>
    <artifactId>kaptcha</artifactId>
    <version>2.3</version>
</dependency>

kaptcha 是一个很有用的验证码生成工具，由于它有许多可配置项，所以用它可以简单快捷的生成各式各样的验证码。

二、使用步骤

前端部分相关代码展示

<div class="login-center clearfix row">
            <div class="col-xs-6">
                <input type="text" id = "validateCode" name="validateCode" class="form-control code" placeholder="验证码" maxlength="5"/>
            </div>
            <div class="col-xs-6">
                <a href="javascript:void(0);" title="点击更换验证码">
                    <img th:src="@{/captcha/captchaImage(type=${'math'})}" class="imgcode"/>
                </a>
            </div>
        </div>

点击图片切换验证码js

$(function () {
        $('.imgcode').click(function () {
            var url = "/captcha/captchaImage?type=math&s=" + Math.random();
            $(".imgcode").attr("src", url);
        });
    });

1.CaptchaController

代码如下（示例）：

@Controller
@RequestMapping("/captcha")
public class CaptchaController {

    @Resource(name = "captchaProducer")
    private Producer captchaProducer;

    @Resource(name = "captchaProducerMath")
    private Producer captchaProducerMath;

    /**
     * 验证码生成
     */
    @GetMapping(value = "/captchaImage")
    public ModelAndView getKaptchaImage(HttpServletRequest request, HttpServletResponse response){

        ServletOutputStream out = null;
        try{
            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");
            String type = request.getParameter("type");
            String capStr = null;
            String code = null;
            BufferedImage bi = null;
            if ("math".equals(type))
            {
                //capText:"6/6=?@1"
                String capText = captchaProducerMath.createText();
                capStr = capText.substring(0, capText.lastIndexOf("@"));
                code = capText.substring(capText.lastIndexOf("@") + 1);
                bi = captchaProducerMath.createImage(capStr);
            }
            else if ("char".equals(type))
            {
                capStr = code = captchaProducer.createText();
                bi = captchaProducer.createImage(capStr);
            }
            session.setAttribute(Constants.KAPTCHA_SESSION_KEY, code);
            out = response.getOutputStream();
            ImageIO.write(bi, "jpg", out);
            out.flush();
        } catch (IOException e) {
            e.printStackTrace();
        }finally
        {
            try
            {
                if (out != null)
                {
                    out.close();
                }
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
        }
        return null;

    }

}

说明：调用captchaProducerMath.createText()方法生成的capText是形如“6/6=?@1”的字符串，使用ImageIO将@前面部分以jpg形式的图片输出，后部分存入session中以备登录时验证，也可整合redis使用，将验证部分存入redis中并设置过期时间。

2.CaptchaConfig

代码如下（示例）：

@Configuration
public class CaptchaConfig {
    @Bean(name = "captchaProducer")
    public DefaultKaptcha getKaptchaBean()
    {
        DefaultKaptcha defaultKaptcha = new DefaultKaptcha();
        Properties properties = new Properties();
        // 是否有边框 默认为true 我们可以自己设置yes，no
        properties.setProperty(KAPTCHA_BORDER, "yes");
        // 验证码文本字符颜色 默认为Color.BLACK
        properties.setProperty(KAPTCHA_TEXTPRODUCER_FONT_COLOR, "black");
        // 验证码图片宽度 默认为200
        properties.setProperty(KAPTCHA_IMAGE_WIDTH, "160");
        // 验证码图片高度 默认为50
        properties.setProperty(KAPTCHA_IMAGE_HEIGHT, "60");
        // 验证码文本字符大小 默认为40
        properties.setProperty(KAPTCHA_TEXTPRODUCER_FONT_SIZE, "38");
        // KAPTCHA_SESSION_KEY
        properties.setProperty(KAPTCHA_SESSION_CONFIG_KEY, "kaptchaCode");
        // 验证码文本字符长度 默认为5
        properties.setProperty(KAPTCHA_TEXTPRODUCER_CHAR_LENGTH, "4");
        // 验证码文本字体样式 默认为new Font("Arial", 1, fontSize), new Font("Courier", 1, fontSize)
        properties.setProperty(KAPTCHA_TEXTPRODUCER_FONT_NAMES, "Arial,Courier");
        // 图片样式 水纹com.google.code.kaptcha.impl.WaterRipple 鱼眼com.google.code.kaptcha.impl.FishEyeGimpy 阴影com.google.code.kaptcha.impl.ShadowGimpy
        properties.setProperty(KAPTCHA_OBSCURIFICATOR_IMPL, "com.google.code.kaptcha.impl.ShadowGimpy");
        Config config = new Config(properties);
        defaultKaptcha.setConfig(config);
        return defaultKaptcha;
    }

    @Bean(name = "captchaProducerMath")
    public DefaultKaptcha getKaptchaBeanMath()
    {
        DefaultKaptcha defaultKaptcha = new DefaultKaptcha();
        Properties properties = new Properties();
        // 是否有边框 默认为true 我们可以自己设置yes，no
        properties.setProperty(KAPTCHA_BORDER, "yes");
        // 边框颜色 默认为Color.BLACK
        properties.setProperty(KAPTCHA_BORDER_COLOR, "105,179,90");
        // 验证码文本字符颜色 默认为Color.BLACK
        properties.setProperty(KAPTCHA_TEXTPRODUCER_FONT_COLOR, "blue");
        // 验证码图片宽度 默认为200
        properties.setProperty(KAPTCHA_IMAGE_WIDTH, "160");
        // 验证码图片高度 默认为50
        properties.setProperty(KAPTCHA_IMAGE_HEIGHT, "50");
        // 验证码文本字符大小 默认为40
        properties.setProperty(KAPTCHA_TEXTPRODUCER_FONT_SIZE, "35");
        // KAPTCHA_SESSION_KEY
        properties.setProperty(KAPTCHA_SESSION_CONFIG_KEY, "kaptchaCodeMath");
        // 验证码文本生成器
        properties.setProperty(KAPTCHA_TEXTPRODUCER_IMPL, "com.tonglei.config.KaptchaTextCreator");
        // 验证码文本字符间距 默认为2
        properties.setProperty(KAPTCHA_TEXTPRODUCER_CHAR_SPACE, "3");
        // 验证码文本字符长度 默认为5
        properties.setProperty(KAPTCHA_TEXTPRODUCER_CHAR_LENGTH, "6");
        // 验证码文本字体样式 默认为new Font("Arial", 1, fontSize), new Font("Courier", 1, fontSize)
        properties.setProperty(KAPTCHA_TEXTPRODUCER_FONT_NAMES, "Arial,Courier");
        // 验证码噪点颜色 默认为Color.BLACK
        properties.setProperty(KAPTCHA_NOISE_COLOR, "white");
        // 干扰实现类
        properties.setProperty(KAPTCHA_NOISE_IMPL, "com.google.code.kaptcha.impl.NoNoise");
        // 图片样式 水纹com.google.code.kaptcha.impl.WaterRipple 鱼眼com.google.code.kaptcha.impl.FishEyeGimpy 阴影com.google.code.kaptcha.impl.ShadowGimpy
        properties.setProperty(KAPTCHA_OBSCURIFICATOR_IMPL, "com.google.code.kaptcha.impl.ShadowGimpy");
        Config config = new Config(properties);
        defaultKaptcha.setConfig(config);
        return defaultKaptcha;
    }
}

3.KaptchaTextCreator

public class KaptchaTextCreator extends DefaultTextCreator
{
    private static final String[] CNUMBERS = "0,1,2,3,4,5,6,7,8,9,10".split(",");

    @Override
    public String getText()
    {
        Integer result = 0;
        Random random = new SecureRandom();
        int x = random.nextInt(10);
        int y = random.nextInt(10);
        StringBuilder suChinese = new StringBuilder();
        int randomoperands = (int) Math.round(Math.random() * 2);
        if (randomoperands == 0)
        {
            result = x * y;
            suChinese.append(CNUMBERS[x]);
            suChinese.append("*");
            suChinese.append(CNUMBERS[y]);
        }
        else if (randomoperands == 1)
        {
            if (!(x == 0) && y % x == 0)
            {
                result = y / x;
                suChinese.append(CNUMBERS[y]);
                suChinese.append("/");
                suChinese.append(CNUMBERS[x]);
            }
            else
            {
                result = x + y;
                suChinese.append(CNUMBERS[x]);
                suChinese.append("+");
                suChinese.append(CNUMBERS[y]);
            }
        }
        else if (randomoperands == 2)
        {
            if (x >= y)
            {
                result = x - y;
                suChinese.append(CNUMBERS[x]);
                suChinese.append("-");
                suChinese.append(CNUMBERS[y]);
            }
            else
            {
                result = y - x;
                suChinese.append(CNUMBERS[y]);
                suChinese.append("-");
                suChinese.append(CNUMBERS[x]);
            }
        }
        else
        {
            result = x + y;
            suChinese.append(CNUMBERS[x]);
            suChinese.append("+");
            suChinese.append(CNUMBERS[y]);
        }
        suChinese.append("=?@" + result);
        return suChinese.toString();
    }
}

4.LoginController

部分代码：

@PostMapping("/login")
    @ResponseBody
    public String loginMe(HttpSession session, String userName, String password, String validateCode) {

        System.out.println("userName :" + userName + " , password :" + password + " , validateCode :" + validateCode);

        Object attribute = session.getAttribute(Constants.KAPTCHA_SESSION_KEY);
        String code = String.valueOf(attribute != null ? attribute : "");
        if (StringUtils.isEmpty(attribute) || !validateCode.equalsIgnoreCase(code)) {
            return ResMesUtil.build().resMesFail("验证码错误！");
        }
        UserEntity user = userService.findByUserNameAndPassword(userName, password);

        if (user != null) {

            session.setAttribute("userName", userName);
            session.setAttribute("userType", user.getUserType());

            return ResMesUtil.build().success();
        }
        return ResMesUtil.build().resMesFail("请输入正确的账号密码！");

    }

本文登录页验证码相关学习，源于开源项目若依，在此附上连接，多多支持开源项目。
若依gitee地址