Hi!!
I have this class:

public class Program implements java.io.Serializable {

     private long programId;
     private Course course;
  
         //With Course mapped this way:
         @ManyToOne(fetch = FetchType.LAZY)
     @JoinColumn(name = "CURS_ID", nullable = false)
     @NotNull
     public CursEscolar getCursEscolar()....etc


}

If I do this query:

List<Program> programs = entityManager.createQuery("From Program p ").getResultList;

I retrieve a list of programs and the course the program belongs OK.

But if I do this other query:

List<Program> programs = entityManager.createQuery("From Program p where p.programId= :progId ")
.setParameter("progId", pro.getProgramId())
.getResultList();

I retrieve the Course with id=0, and the fields null. The only difference is the condition:

p.programId= :progId

Why happens this??