This happens for NonstrictReadWriteCache and for ReadWriteCache when the application needs to be restarted or stopped.

2005-03-18 11:49:45,977 WARN net.sf.hibernate.cache.ReadWriteCache - could not destroy cache
java.lang.NullPointerException
        at com.opensymphony.oscache.plugins.clustersupport.JavaGroupsBroadcastingListener.finialize(JavaGroupsBroadcastingListener.java:135)
        at com.opensymphony.oscache.base.AbstractCacheAdministrator.finalizeListeners(AbstractCacheAdministrator.java:367)
        at com.opensymphony.oscache.general.GeneralCacheAdministrator.destroy(GeneralCacheAdministrator.java:192)
        at net.sf.hibernate.cache.OSCache.destroy(OSCache.java:59)
        at net.sf.hibernate.cache.ReadWriteCache.destroy(ReadWriteCache.java:219)
        at net.sf.hibernate.impl.SessionFactoryImpl.close(SessionFactoryImpl.java:545)
        at com.ldspromise.db.util.HibernateUtil.destroy(HibernateUtil.java:52)

Basically, the line bus.stop() is called when bus is already null.

I think there may be a more involved problem here though because bus should probably not be null. ie: was bus ever not null?

To reproduce, all you have to do is have a hibernate class that uses cache="read-write" or cache="nonstrict-read-write" configured in hibernate. Then try stopping the application.