org.hibernate.MappingException: Could not determine type for: java.util.List, at table: College, for columns: [org.hibernate.mapping.Column(students)]

You are using field access strategy (determined by @Id annotation). Put any JPA related annotation right above each field instead of getter property

@OneToMany(targetEntity=Student.class, mappedBy="college", fetch=FetchType.EAGER)
private List<Student> students;

Adding the @ElementCollection to the List field solved this issue:

    @Column
    @ElementCollection(targetClass=Integer.class)
    private List<Integer> countries;

Problem with Access strategies

As a JPA provider, Hibernate can introspect both the entity attributes (instance fields) or the accessors (instance properties). By default, the placement of the @Id annotation gives the default access strategy. When placed on a field, Hibernate will assume field-based access. Placed on the identifier getter, Hibernate will use property-based access.

Field-based access

When using field-based access, adding other entity-level methods is much more flexible because Hibernate won’t consider those part of the persistence state

@Entity
public class Simple {

@Id
private Integer id;

@OneToMany(targetEntity=Student.class, mappedBy="college", 
fetch=FetchType.EAGER)
private List<Student> students;

//getter +setter
}

Property-based access

When using property-based access, Hibernate uses the accessors for both reading and writing the entity state

@Entity
public class Simple {

private Integer id;
private List<Student> students;

@Id
public Integer getId() {
    return id;
}

public void setId( Integer id ) {
    this.id = id;
}
@OneToMany(targetEntity=Student.class, mappedBy="college", 
fetch=FetchType.EAGER)
public List<Student> getStudents() {
   return students;
}
public void setStudents(List<Student> students) {
    this.students = students;
}

}

But you can't use both Field-based and Property-based access at the same time. It will show like that error for you

For more idea follow this