1.https://javabydeveloper.com/jpa-entity-lifecycle-jpa-developer-should-know/
2.https://openjpa.apache.org/builds/1.2.3/apache-openjpa/docs/jpa_overview_em_lifecycle.html
3.。https://techrocking.com/jpa-entity-life-cycle-and-persistence-context/#Conclusion
4.https://www.javaguides.net/2019/01/jpa-entity-object-life-cycle-new-managed-removed-detached.html
5.https://www.objectdb.com/java/jpa/persistence/managed#Entity_Object_Life_Cycle