[FIXED] JPA Entity class without "@Column" annotation

Issue

I have this piece of code where the author creates a JPA Entity. Somehow, it's successfully working and that seems weird to me since not every field is annotated with "@Column". Based on that, here's my question:

How it is possible for this class to work properly (all data is being successfully recorded in the database) without every field not having a "Column" annotation (excepting "id")?

/**
     * @author Ram Alapure
     * @since 05-04-2017
     */
   
    @Entity
    @Table(name="User")
    public class User {
    
        @Id
        @GeneratedValue(strategy=GenerationType.IDENTITY)
        @Column(name = "id", updatable = false, nullable = false)
        private long id;
        
    private String firstName;
    
    private String lastName;
    
    private LocalDate dob;
    
    private String gender;
    
    private String role;
    
    private String email;
    
    private String password;

    @Override
    public String toString() {
        return "User [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", dob=" + dob + ", email="
                + email + "]";
    }

    
}

For instance, here's another class which is working properly as well. But this time, with a "@Column" annotation in every field. I thought it was a pre-requisite to JPA create a column from the field.

  @Entity
@Table(name = "address")
public class Address {
    
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "address_id")
    private long id;
    
    @Column(name = "rua")
    private String street;
    
    @Column(name = "number")
    private int number;
    
    @Column(name = "complement")
    private String complement;
    
    @Column(name = "suburb")
    private String suburb;
    
    @Column(name = "city")
    private String city;
    
    @Column(name = "state")
    private String state;
    
    @Column(name = "country")
    private String country;
    
    @Column(name = "cep")

Getters and Setters were hidden from all pieces of code since they just look like regular getters and setters, not being necessary to be shown.

Solution

If you don't specify @Column annotation (Optional) then Hibernate uses default naming stretegy by using camel case.

firstName field becomes first_name column in Database.

You can also define your own naming stretegy according to your needs.

From the documentation.

strategy ; Hibernate 5 defines a Physical and Implicit naming strategies. Spring Boot configures SpringPhysicalNamingStrategy by default. This implementation provides the same table structure as Hibernate 4: all dots are replaced by underscores and camel cases are replaced by underscores as well.

Answered By - Alien