MappedSuperclass

Many entities share fields: id, audit columns, maybe a version. A @MappedSuperclass is a parent class whose fields are copied into each child's table. It is not an entity itself: no table, no repository, no polymorphic queries.

@MappedSuperclass
@EntityListeners(AuditingEntityListener.class)
public abstract class BaseEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @CreatedDate @Column(updatable = false) private Instant createdAt;
    @LastModifiedDate                      private Instant updatedAt;

    public Long getId() { return id; }
}

@Entity @Table(name = "products")   public class Product  extends BaseEntity { private String name; ... }
@Entity @Table(name = "categories") public class Category extends BaseEntity { private String name; }

create table products   (id bigint not null auto_increment, created_at datetime(6), updated_at datetime(6), name varchar(255), ..., primary key (id));
create table categories (id bigint not null auto_increment, created_at datetime(6), updated_at datetime(6), name varchar(255), primary key (id));