<dependencies> <dependency> <groupId>com.github.axet</groupId> <artifactId>kaptcha</artifactId> <version>0.0.6</version> </dependency> </dependencies> 

package com.example.controller; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestMethod; import org.springframework.web.bind.annotation.RequestParam; import org.springframework.web.servlet.ModelAndView; import com.google.code.kaptcha.servlet.KaptchaExtend; @Controller public class RegisterKaptchaController extends KaptchaExtend { @RequestMapping(value = "/captcha.jpg", method = RequestMethod.GET) public void captcha(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { super.captcha(req, resp); } @RequestMapping(value = "/register", method = RequestMethod.GET) public ModelAndView registerGet(@RequestParam(value = "error", required = false) boolean failed, HttpServletRequest request) { ModelAndView model = new ModelAndView("register-get"); // // model MUST contain HTML with <img src="/captcha.jpg" /> tag // return model; } @RequestMapping(value = "/register", method = RequestMethod.POST) public ModelAndView registerPost(@RequestParam(value = "email", required = true) String email, @RequestParam(value = "password", required = true) String password, HttpServletRequest request) { ModelAndView model = new ModelAndView("register-post"); if (email.isEmpty()) throw new RuntimeException("email empty"); if (password.isEmpty()) throw new RuntimeException("empty password"); String captcha = request.getParameter("captcha"); if (!captcha.equals(getGeneratedKey(request))) throw new RuntimeException("bad captcha"); // // eveyting is ok. proceed with your user registration / login process. // return model; } }