I guess the problem is with the code for configuration you mentioned for .hbm.xml may not be working in Tomcat.
I think it needs AnnotationConfiguration object. I guess you used this code due to the Annotationconfiguration object creation is not working.
Better create a maven hibernate project with pom and export the war file to Tomcat (with the changes of Annotationconfiguration). Also use log4j jar for showing the details of Tomcat execution with the debug outputs, so that Tomcat output will print all of execution flow.