为什么没显示？

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
<!--<servlet>
    <servlet-name>myservlet</servlet-name>
    <servlet-class>com.gyc.text.myservlet</servlet-class>
</servlet>
    <servlet-mapping>
        <servlet-name>myservlet</servlet-name>
        <url-pattern>/myservlet</url-pattern>
    </servlet-mapping>-->
    <servlet>
        <servlet-name>kaptcha</servlet-name>
        <servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>kaptcha</servlet-name>
        <url-pattern>/kaptcha.jpg</url-pattern>
    </servlet-mapping>
</web-app>