Servlet failed with Exception  java.lang.NullPointerException  at weblogic.servlet.internal.ServletResponseImpl.sendError(ServletResponseImpl.java:610)         at org.apache.struts2.dispatcher.Dispatcher.sendError(Dispatcher.java:770)         at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:505)         at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)         at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)         Truncated. see log file for complete stacktrace