<p>What is appropriate way to integrate SpringSecurity with Capcha ? </p>

<p>I have following use case :
When user will tries to login, if we he failed to login N times, captcha will be displayed, so authentication will be using three parameters : username, password, captcha. But Spring Security doesn't support built in Captcha handling. </p>

<p>I just start thinking about implementation. And have following variants:</p>

<ul>
<li>Adding separate security filter in Spring Security filter stack, </li>
<li>Entirely rewrite AuthenticationProcessingFilter to support some Captcha</li>
<li>Use some programmatic authentication with interception captcha logic and then transfering username and password to Spring Security</li>
</ul>

<p>As a Captcha implementation I think about JCaptcha, but what your thougths?</p>

As an alternative to using JCaptcha, if you'd like to use the
reCAPTCHA Service
on your site, then check out the free Section 4.4 (
direct PDF link
) of the new
Spring in Practice
book (currently in beta).
This shows you integration with Spring MVC and Spring Validation. Since the integration is on the front-end, w/external APIs, Spring Security doesn't really come into the picture here.
I am not sure what your use case is? Are you hoping to use captchas as an alternative to authentication to prove "human"-ness?