Shrio中的验证码案例

Shrio中的验证码（Captcha）案例可参考如下：

配置Shiro的Filter

在Shiro的配置文件中，需要配置一个过滤器（Filter）来处理验证码的校验。代码如下：

<filter>
  <filter-name>captchaFilter</filter-name>
  <filter-class>com.example.CaptchaFilter</filter-class>
</filter>
<filter-mapping>
  <filter-name>captchaFilter</filter-name>
  <url-pattern>/login</url-pattern>
</filter-mapping>

编写CaptchaFilter

CaptchaFilter继承了Shiro原有的FormAuthenticationFilter，重写了其中的onLoginFailure方法，在该方法中对验证码进行校验，如果校验失败则返回错误信息。代码如下：

public class CaptchaFilter extends FormAuthenticationFilter {
 
  private String captchaParam = "captcha";
 
  public String getCaptchaParam() {
    return captchaParam;
  }
 
  public void setCaptchaParam(String captchaParam) {
    this.captchaParam = captchaParam;
  }
 
  @Override
  protected boolean onLoginFailure(AuthenticationToken token, AuthenticationException e, ServletRequest request, ServletResponse response) {
    CaptchaToken captchaToken = (CaptchaToken) token;
    HttpServletRequest httpServletRequest = (HttpServletRequest) request;
    String captcha = httpServletRequest.getParameter(captchaParam);
    HttpSession session = httpServletRequest.getSession();
    String sessionCaptcha = (String) session.getAttribute("captcha");
    if (captcha == null || !captcha.equalsIgnoreCase(sessionCaptcha)) {
      request.setAttribute("shiroLoginFailure", "captchaError");
      return true;
    }
    return super.onLoginFailure(token, e, request, response);
  }
}

生成验证码

在登录页面中，需要生成验证码并将其显示出来。代码如下：

@RequestMapping("/captcha")
public void captcha(HttpServletRequest request, HttpServletResponse response) throws Exception {
  Captcha captcha = new DefaultCaptcha();
  String code = captcha.generateCode();
  HttpSession session = request.getSession();
  session.setAttribute("captcha", code);
  BufferedImage image = captcha.generateImage(code);
  ServletOutputStream out = response.getOutputStream();
  ImageIO.write(image, "JPEG", out);
  try {
    out.flush();
  } finally {
    out.close();
  }
}

登录页面中的验证码

在登录页面中，需要添加一个验证码输入框，并将验证码图片显示出来。代码如下：

<form method="post" action="/login">
  <input type="text" name="username" placeholder="Username" required>
  <input type="password" name="password" placeholder="Password" required>
  <input type="text" name="captcha" placeholder="Captcha" required>
  <img src="/captcha" onclick="this.src='/captcha?'+Math.random()" title="点击刷新验证码">
  <button type="submit">Login</button>
</form>

以上是Shrio中的验证码案例的大致实现思路，具体实现还需要根据项目需求进行调整和完善