It is possible that after an upgrade you may encounter this error on some of the more complex pages and root cause provided by tomcat console is : Unable to compile class for JSP The code of method _jspService(HttpServletRequest, HttpServletResponse)
Velocity generates NullPointerException while evaluating template
While evaluating template with Velocity I am affecting a null point exception but happened only on production environment because it seems that the application is trying to write to tomcat/bin the velocity.log file but it failed due to the permission.