// domain/entities/Product.java
@Entity
@Table(name = "products")
public class Product {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "product_name", nullable = false)
    private String name;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "category_id")
    private Category category;

    @Version
    private Long version;

    // Entity is coupled to JPA, cannot exist without Hibernate
}

// domain/entities/Product.java
public class Product {
    private final ProductId id;
    private String name;
    private CategoryId categoryId;
    private Money price;

    public Product(ProductId id, String name, CategoryId categoryId, Money price) {
        this.id = id;
        this.name = validateName(name);
        this.categoryId = categoryId;
        this.price = price;
    }

    public void updatePrice(Money newPrice, PricingPolicy policy) {
        if (!policy.allowsPrice(newPrice)) {
            throw new InvalidPriceException(newPrice);
        }
        this.price = newPrice;
    }

    private String validateName(String name) {
        if (name == null || name.isBlank()) {
            throw new InvalidProductNameException();
        }
        return name.trim();
    }
}

// infrastructure/persistence/jpa/JpaProductEntity.java
@Entity
@Table(name = "products")
class JpaProductEntity {
    @Id private Long id;
    @Column private String name;
    // ORM mapping isolated to infrastructure
}

// infrastructure/persistence/jpa/ProductMapper.java
class ProductMapper {
    Product toDomain(JpaProductEntity entity) { /* ... */ }
    JpaProductEntity toJpa(Product product) { /* ... */ }
}