Hibernate MappingException: Unknown entity on session save

java,hibernate,mappingexception

Add @Entity to DrAction class, and add <mapping class="your.package.DrAction"/> to hibernate.cfg.xml. @Entity @Table(name = "dr_action") public class DrAction implements java.io.Serializable { hibernate.cfg.xml ... <session-factory> .... <mapping class="your.package.DrAction"/> </session-factory> .... UPDATE You are probably using Oracle as DB, and Oracle doesn't support auto generated ids. You'll have to specify sequence that...