JPA entity id - primitive or object type (long or Long)

Question

Should the ID of your Entity be long (primitive type) or Long (object type)?

• The ID is the primary key of my table and is never 'null' in the database.
• My co-workers suggest to use an Object Type Long.
• Hibernate Reverse Engineering tool generates a primitive type long for id by default.

What to choose? long or Long?

@Entity
@Table(name = "COUNTRY")
public class CountryEntity implements java.io.Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @Column(name = "ID")
    private long id;
    @Column(name = "NAME")
    private String name;
    @Column(name = "CURRENCY")
    private String currency;
    @Column(name = "PEOPLE")
    private Long people;
    @Column(name = "SIZE")
    private Long size;

    public CountryEntity() {
    }

Answer 1

I consider having Long is better, as it is more correct to check whether an entity has persistent identity by checking against the null value (in MySQL you can have an ID of value 0). Also some libraries like Spring base(d) on an ID of type Long (by default) in their logic. See this implementation for an example.

The small advantage of the primitive: it takes a bit less space.

PS:Both are correct & supported according to the JPA specification and the answers to this question are somehow opinion-based.

Answer 2

I'd prefer Long, for the simple reason that if you let the database generate ids for you (which you should), you can tell that a recently instantiated CountryEntity object is not yet persisted by checking for id==null. If you use long, then id will always have a non-null value (initially 0), which will change upon persisting the entity.

Answer 3

Use a String type for your entity id. Numeric types are intended for sequences or performing mathematical comparison and computations. If using a guid/uuid generator for id, you'll likely need to allow for non-numeric characters anyway (e.g. hyphens).