Kaptcha验证码生成器

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

	<!-- Kaptcha验证码生成器 -->
	<bean id="captchaProducer" class="com.google.code.kaptcha.impl.DefaultKaptcha" scope="singleton">
	    <property name="config">
	        <bean class="com.google.code.kaptcha.util.Config">
	            <constructor-arg>
	                <props>
	                	<prop key="kaptcha.session.key">kaptcha.code</prop>  
	                	<!-- 无边框 -->
	                    <prop key="kaptcha.border">no</prop>
	                    <prop key="kaptcha.textproducer.font.color">black</prop>
	                    <!-- 渲染效果：水纹：WaterRipple；鱼眼：FishEyeGimpy；阴影：ShadowGimpy -->
	                    <prop key="kaptcha.obscurificator.impl">com.google.code.kaptcha.impl.WaterRipple</prop>
	                    <!-- 不要噪点 -->
	                    <prop key="kaptcha.noise.impl">com.google.code.kaptcha.impl.NoNoise</prop>
	                    <prop key="kaptcha.image.width">90</prop>
	                    <prop key="kaptcha.image.height">33</prop>
	                    <prop key="kaptcha.textproducer.font.size">25</prop>
	                    <prop key="kaptcha.textproducer.char.length">4</prop>
	                    <prop key="kaptcha.textproducer.char.space">5</prop>
	                    <!-- 和登录框背景颜色一致 -->
	                    <prop key="kaptcha.background.clear.from">247,247,247</prop>
	                    <prop key="kaptcha.background.clear.to">247,247,247</prop>
	                </props>
	            </constructor-arg>
	        </bean>
	    </property>
	</bean>

    /**
     * 验证码
     *
     * @param rsp
     * @param session
     */
    @RequestMapping(value = "captcha.html", method = RequestMethod.GET)
    public void kaptcha(HttpServletResponse rsp, HttpSession session) {
        try (ServletOutputStream out = rsp.getOutputStream()) {
            rsp.setDateHeader("Expires", 0);
            rsp.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");
            rsp.addHeader("Cache-Control", "post-check=0, pre-check=0");
            rsp.setHeader("Pragma", "no-cache");
            rsp.setContentType("image/jpeg");

            String capText = captchaProducer.createText();
            //将验证码存入shiro 登录用户的session
            session.setAttribute(Constants.KAPTCHA_SESSION_KEY, capText);
            BufferedImage image = captchaProducer.createImage(capText);
            ImageIO.write(image, "jpg", out);
            out.flush();
        } catch (IOException e) {
            throw new SystemException(e);
        }
    }