Download and configure Tomcat 9 to run with JDK 9 ea b124
source: https://tomcat.apache.org/download-90.cgi#9.0.0.M8
Load http://localhost:8080/ page
returns,
HTTP Status 500 - java.lang.ClassNotFoundException: org.apache.jsp.index_jsp


type Exception report

message java.lang.ClassNotFoundException: org.apache.jsp.index_jsp

description The server encountered an internal error that prevented it from fulfilling this request.

exception
org.apache.jasper.JasperException: java.lang.ClassNotFoundException: org.apache.jsp.index_jsp
org.apache.jasper.servlet.JspServletWrapper.getServlet(JspServletWrapper.java:176)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:380)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)


root cause
java.lang.ClassNotFoundException: org.apache.jsp.index_jsp
java.net.URLClassLoader.findClass(java.base@9-ea/URLClassLoader.java:384)
org.apache.jasper.servlet.JasperLoader.loadClass(JasperLoader.java:129)
org.apache.jasper.servlet.JasperLoader.loadClass(JasperLoader.java:60)
org.apache.jasper.servlet.JspServletWrapper.getServlet(JspServletWrapper.java:171)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:380)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
note The full stack trace of the root cause is available in the Apache Tomcat/9.0.0.M8 logs.
==============
From the log it appears that the ClassLoader in JDK 9 fails to trigger creation of GC Daemon thread during Tomcat start which is expected in non-Sun JVMs.
---------------
 java.lang.ClassNotFoundException: sun.misc.GC
        at java.net.URLClassLoader.findClass(java.base@9-ea/URLClassLoader.java:
384)
----------------
For details refer to attached logs.

This works fine with 8u91.