JPA troubleshooting this morning i got an error while inseritng an entity in the db Unknown entity bean class: class model.Doctor, please verify that this class has been marked with the @Entity annotation. the class is already having @Entity annotation , everything is set correctly only small thing i noticed ..the id is defined as int because during the process this bean is being populated from another bean and assigning int value to the id. Solution ..by changing both beans from int to long this error disappeard :) another error happend with glass fish server java.lang.IllegalArgumentException: Object: is not a known entity type. this when deploying an app and glass fish did not wake up yet to realize that the version of the class is changed solution ..simply restart glassfish :D