In JbpmSessionFactory there is the following code:

// check if the properties in the hibernate.cfg.xml need to be overwritten by a separate properties file.
String hibernatePropertiesResource = JbpmConfiguration.Configs.getString("resource.hibernate.properties");
if (hibernatePropertiesResource!=null) {
...

This is supposed to skip the hibernate.properties part if resource.hibernate.properties it is not defined in jbpm.cfg.xml. However, Configs.getString() does not return null if a property is undefined, but throws an exception. So there's no way to use JbpmSessionFactory without hibernate.properties file.

This is a minor issue, but makes an upgrade more difficult for people who use this class, and it should be pretty easy to fix.