Spring MVC中使用Google kaptcha验证码的方法详解

<!-- google 验证码 -->
<dependency>
 <groupId>com.github.penggle</groupId>
 <artifactId>kaptcha</artifactId>
 <version>${kaptcha.version}</version>
</dependency>

<img id="kaptchaImage" src="${pageContext.request.contextPath}/captcha-image" width="116" height="36">

$(function(){
 $('#kaptchaImage').click(function () {
  $(this).hide().attr('src', '${ctx}/captcha-image?' + Math.floor(Math.random()*100) ).fadeIn();
  event.cancelBubble=true;
 });
 });

<!--goole captcha 验证码配置-->
 <bean id="captchaProducer" class="com.google.code.kaptcha.impl.DefaultKaptcha">
 <property name="config">
  <bean class="com.google.code.kaptcha.util.Config">
  <constructor-arg>
   <props>
   <prop key="kaptcha.border">no</prop>
   <prop key="kaptcha.textproducer.font.size">45</prop>
   <prop key="kaptcha.textproducer.font.color">blue</prop>
   <prop key="kaptcha.textproducer.char.length">4</prop>
   <prop key="kaptcha.session.key">code</prop>
   </props>
  </constructor-arg>
  </bean>
 </property>
 </bean>

@Controller
public class CaptchaController {

 private final Producer captchaProducer;

 @Autowired
 public CaptchaController(Producer captchaProducer) {
 this.captchaProducer = captchaProducer;
 }

 @RequestMapping(value = "captcha-image")
 public String getKaptchaImage(HttpServletRequest request, HttpServletResponse response) throws Exception {
 response.setDateHeader("Expires", 0);
 response.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");
 response.addHeader("Cache-Control", "post-check=0, pre-check=0");
 response.setHeader("Pragma", "no-cache");
 response.setContentType("image/jpeg");

 String capText = captchaProducer.createText();
 request.getSession().setAttribute(Constants.KAPTCHA_SESSION_KEY, capText);
 BufferedImage bi = captchaProducer.createImage(capText);
 ServletOutputStream out = response.getOutputStream();
 ImageIO.write(bi, "jpg", out);

 try {
  out.flush();
 } finally {
  out.close();
 }
 return null;
 }
}

request.getSession().getAttribute(Constants.KAPTCHA_SESSION_KEY);