exception 
javax.servlet.ServletException
        org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:290)
        org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:161)

root cause 
java.lang.ExceptionInInitializerError
        java.lang.Class.forName0(Native Method)
        java.lang.Class.forName(Class.java:169)
        Gb.Servlet.doGet(Unknown Source)
        javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
        javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
        sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        java.lang.reflect.Method.invoke(Method.java:597)
        org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:243)
        java.security.AccessController.doPrivileged(Native Method)
        javax.security.auth.Subject.doAsPrivileged(Subject.java:517)
        org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:272)
        org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:161)