I get the following exception when trying to persist a computer science Department object after setting Department.id = 1:

Exception in thread "main" javax.persistence.PersistenceException: org.hibernate.PersistentObjectException: detached entity passed to persist: lab2.model.Department

    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:154)

    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:181)

    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:188)

    at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:795)

    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:773)

    at lab2.main.Lab2.main(Lab2.java:56)....

When I instead insert the users, department, and search into the database using mysql, I get the following exception when querying for department with id = 1: 

Exception in thread "main" javax.persistence.PersistenceException: org.hibernate.type.SerializationException: could not deserialize

    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:154)

    at org.hibernate.query.internal.AbstractProducedQuery.list(AbstractProducedQuery.java:1534)

    at org.hibernate.query.internal.AbstractProducedQuery.getSingleResult(AbstractProducedQuery.java:1573)

    at lab2.main.Lab2.main(Lab2.java:65)...

When I google these exceptions most of the results point to the annotations. My only guess is that it may be because of the annotations for Department.searches  and Search.department. Heres how I annotated them: 

 @OneToMany(mappedBy = "department")

 @OrderBy( "createdOn asc" )   

private List<Search> searches;

 @ManyToOne

   private Department department;

Does anybody have any idea what may be causing this?