<dependency>  <groupId>com.github.penggle</groupId>  <artifactId>kaptcha</artifactId>  <version>2.3.2</version></dependency>

<servlet> <!-- 生成圖片的Servlet --> <servlet-name>Kaptcha</servlet-name> <servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class> <!-- 是否有邊框 --> <init-param>         <param-name>kaptcha.border</param-name> <param-value>no</param-value> </init-param> <!-- 字體顏色 --> <init-param>   <param-name>kaptcha.textproducer.font.color</param-name> <param-value>red</param-value> </init-param> <!-- 圖片寬度 --> <init-param> <param-name>kaptcha.image.width</param-name> <param-value>135</param-value> </init-param> <!-- 使用哪些字符生成驗證碼 --> <init-param> <param-name>kaptcha.textproducer.char.string</param-name>  <param-value>ACDEFHKPRSTWX345679</param-value> </init-param> <!-- 圖片高度 --> <init-param>  <param-name>kaptcha.image.height</param-name>  <param-value>50</param-value> </init-param> <!-- 字體大小 --> <init-param>  <param-name>kaptcha.textproducer.font.size</param-name>  <param-value>43</param-value> </init-param> <!-- 干擾線的顏色 --> <init-param>  <param-name>kaptcha.noise.color</param-name>  <param-value>black</param-value> </init-param> <!-- 字符個數 --> <init-param>  <param-name>kaptcha.textproducer.char.length</param-name>  <param-value>4</param-value> </init-param> <!-- 使用哪些字體 --> <init-param>  <param-name>kaptcha.textproducer.font.names</param-name>  <param-value>Arial</param-value> </init-param> </servlet> <!-- 映射的url --> <servlet-mapping> <servlet-name>Kaptcha</servlet-name> <url-pattern>/Kaptcha</url-pattern> </servlet-mapping>

<div class="item-inner"> <label for="j_captcha" class="item-title label">驗證碼</label> <input id="j_captcha" name="j_captcha" type="text"   class="form-control in" placeholder="驗證碼" /> <div class="item-input">   <img id="captcha_img"         onclick="changeVerifyCode(this)" src="../Kaptcha" /> </div></div>

var verifyCodeActual = $('#j_captcha').val(); if (!verifyCodeActual) {  $.toast('請輸入驗證碼！');  return; } formData.append("verifyCodeActual", verifyCodeActual);

function changeVerifyCode(img) { img.src = "../Kaptcha?" + Math.floor(Math.random() * 100);}

import javax.servlet.http.HttpServletRequest;public class CodeUtil { public static boolean checkVerifyCode(HttpServletRequest request) { String verifyCodeExpected = (String) request.getSession().getAttribute(  com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY); String verifyCodeActual = HttpServletRequestUtil.getString(request,  "verifyCodeActual"); if (verifyCodeActual == null  || !verifyCodeActual.equalsIgnoreCase(verifyCodeExpected)) {  return false; } return true; }}

import javax.servlet.http.HttpServletRequest;public class HttpServletRequestUtil { public static int getInt(HttpServletRequest request, String name) { try {  return Integer.decode(request.getParameter(name)); } catch (Exception e) {  return -1; } } public static long getLong(HttpServletRequest request, String name) { try {  return Long.valueOf(request.getParameter(name)); } catch (Exception e) {  return -1; } } public static Double getDouble(HttpServletRequest request, String name) { try {  return Double.valueOf(request.getParameter(name)); } catch (Exception e) {  return -1d; } } public static Boolean getBoolean(HttpServletRequest request, String name) { try {  return Boolean.valueOf(request.getParameter(name)); } catch (Exception e) {  return false; } } public static String getString(HttpServletRequest request, String name) { try {  String result = request.getParameter(name);  if (result != null) {  result = result.trim();  }  if ("".equals(result))  result = null;  return result; } catch (Exception e) {  return null; } }}