hibernate-demo/src/main/java/com/ankurm/hibernatedemo/naturalid/NaturalIdEqualsEntity.java

package com.ankurm.hibernatedemo.naturalid;

import jakarta.persistence.Column;
import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.Id;
import java.util.Objects;
import org.hibernate.Hibernate;
import org.hibernate.annotations.NaturalId;

/**
 * equals()/hashCode() based on the IMMUTABLE natural id (sku), assigned in the constructor --
 * exactly the pattern posts 4864/4865 recommend. Since sku is set before the object ever enters
 * a Set/Map (unlike a surrogate id, which is null until flush), the hash code should be STABLE
 * across persist(). This entity exists to test whether that advice actually holds up.
 *
 * <p>Docs: docs/06-natural-ids.md, Topic 3.
 */
@Entity
public class NaturalIdEqualsEntity {

    @Id
    @GeneratedValue
    private Long id;

    @NaturalId
    @Column(nullable = false, unique = true, updatable = false)
    private final String sku;

    private String name;

    protected NaturalIdEqualsEntity() {
        this.sku = null; // JPA no-arg constructor requirement
    }

    public NaturalIdEqualsEntity(String sku, String name) {
        this.sku = sku;
        this.name = name;
    }

    public Long getId() {
        return id;
    }

    public String getSku() {
        return sku;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null) return false;
        if (Hibernate.getClass(this) != Hibernate.getClass(o)) return false;
        NaturalIdEqualsEntity that = (NaturalIdEqualsEntity) o;
        return Objects.equals(sku, that.sku);
    }

    @Override
    public int hashCode() {
        return Objects.hash(sku);
    }
}