Spring boot+Shiro+kaptcha实现图形验证码

我自己也是在学习当中，有什么问题请轻喷。
参考学习若依项目实现验证码功能

1.pom.xml中导入依赖

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

2. 实现前端页面

<div>
        <form method="post" class="layui-form">
            <input name="username" placeholder="用户名" value="admin" type="text" lay-verify="required"
                   class="layui-input">
            <hr class="hr15">
            <input name="password" lay-verify="required" value="123456" placeholder="密码" type="password"
                   class="layui-input">
            <hr class="hr15">
            <div class="layui-row" th:if="${captchaEnabled==true}">
                <div class="layui-input-inline " style="width: 40%">
                    <input autocomplete="off" lay-verify="required" type="text" name="validateCode" class="form-control code" placeholder="验证码" maxlength="5"/>
                </div>
                <div class="layui-inline " style="float: right;display: block;width: auto;">
                    <a href="javascript:void(0);" title="点击更换验证码">
                        <img th:src="@{captcha/captchaImage(type=${captchaType})}" class="imgcode" width="60%"/>
                    </a>
                </div>
            </div>

            <hr class="hr15">
            <input value="登录" lay-submit lay-filter="login" style="width:100%;" type="submit">
            <hr class="hr20">

        </form>
    </div>