MS Lesson11: Entity relations

1. One to One relationship

package guru.springframework.cruddemo.entity;

import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.OneToOne;
import lombok.Getter;
import lombok.RequiredArgsConstructor;
import lombok.Setter;
import lombok.ToString;
import org.hibernate.proxy.HibernateProxy;

import java.util.Objects;

@Getter
@Setter
@Entity
@ToString
@RequiredArgsConstructor
public class Student {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private String surname;
    private String pin;
    private Integer age;

    @OneToOne(mappedBy = "student")
    private Profile profile;

    @Override
    public final boolean equals(Object o) {
        if (this == o) return true;
        if (o == null) return false;
        Class<?> oEffectiveClass = o instanceof HibernateProxy ? ((HibernateProxy) o).getHibernateLazyInitializer().getPersistentClass() : o.getClass();
        Class<?> thisEffectiveClass = this instanceof HibernateProxy ? ((HibernateProxy) this).getHibernateLazyInitializer().getPersistentClass() : this.getClass();
        if (thisEffectiveClass != oEffectiveClass) return false;
        Student student = (Student) o;
        return getId() != null && Objects.equals(getId(), student.getId());
    }

    @Override
    public final int hashCode() {
        return this instanceof HibernateProxy ? ((HibernateProxy) this).getHibernateLazyInitializer().getPersistentClass().hashCode() : getClass().hashCode();
    }

} 

package guru.springframework.cruddemo.entity;

import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.JoinColumn;
import jakarta.persistence.OneToOne;
import lombok.Getter;
import lombok.RequiredArgsConstructor;
import lombok.Setter;
import lombok.ToString;
import org.hibernate.proxy.HibernateProxy;

import java.util.Objects;

@Getter
@Setter
@Entity
@ToString
@RequiredArgsConstructor
public class Profile {

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

    @OneToOne
    @ToString.Exclude
    @JoinColumn(name = "student_id", unique = true)
    private Student student;

    @Override
    public final boolean equals(Object o) {
        if (this == o) return true;
        if (o == null) return false;
        Class<?> oEffectiveClass = o instanceof HibernateProxy ? ((HibernateProxy) o).getHibernateLazyInitializer().getPersistentClass() : o.getClass();
        Class<?> thisEffectiveClass = this instanceof HibernateProxy ? ((HibernateProxy) this).getHibernateLazyInitializer().getPersistentClass() : this.getClass();
        if (thisEffectiveClass != oEffectiveClass) return false;
        Profile profile = (Profile) o;
        return getId() != null && Objects.equals(getId(), profile.getId());
    }

    @Override
    public final int hashCode() {
        return this instanceof HibernateProxy ? ((HibernateProxy) this).getHibernateLazyInitializer().getPersistentClass().hashCode() : getClass().hashCode();
    }
}

@JoinColumn foreignKey owning side-da qoyulur.

MappedBy - bidirectional relationlarda istifade olunur, ve foreignKey-ni kim idare edir sualina cavab verir.