[Java Spring] @Embeddable and @EmbeddedId

In software, we come across many use cases when we need to have a composite primary key to define an entry in a table. Composite primary keys are keys that use more than one column to identify a row in the table uniquely.

We represent a composite primary key in Spring Data by using the @Embeddable annotation on a class. This key is then embedded in the table's corresponding entity class as the composite primary key by using the @EmbeddedId annotation on a field of the @Embeddable type.

 

package com.example.ec.domain;

import javax.persistence.Column;
import javax.persistence.EmbeddedId;
import javax.persistence.Entity;
import java.util.Objects;

@Entity
public class TourRating {
    @EmbeddedId
    private TourRatingPk pk;

    @Column(nullable = false)
    private Integer score;

    @Column
    private String comment;

    public TourRating(TourRatingPk pk, Integer score, String comment) {
        this.pk = pk;
        this.score = score;
        this.comment = comment;
    }

    public TourRating() {
    }

    @Override
    public String toString() {
        return "TourRating{" +
                "pk=" + pk +
                ", score=" + score +
                ", comment='" + comment + '\'' +
                '}';
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        TourRating that = (TourRating) o;
        return Objects.equals(pk, that.pk) &&
                Objects.equals(score, that.score) &&
                Objects.equals(comment, that.comment);
    }

    @Override
    public int hashCode() {
        return Objects.hash(pk, score, comment);
    }

    public TourRatingPk getPk() {
        return pk;
    }

    public void setPk(TourRatingPk pk) {
        this.pk = pk;
    }

    public Integer getScore() {
        return score;
    }

    public void setScore(Integer score) {
        this.score = score;
    }

    public String getComment() {
        return comment;
    }

    public void setComment(String comment) {
        this.comment = comment;
    }
}

 

package com.example.ec.domain;

import javax.persistence.Column;
import javax.persistence.Embeddable;
import javax.persistence.ManyToOne;
import java.io.Serializable;

@Embeddable
public class TourRatingPk implements Serializable {
    @ManyToOne
    private Tour tour;

    @Column(insertable = false, updatable = false,nullable = false)
    private Integer customerId;

    public TourRatingPk(Tour tour, Integer customerId) {
        this.tour = tour;
        this.customerId = customerId;
    }

    public Tour getTour() {
        return tour;
    }

    public Integer getCustomerId() {
        return customerId;
    }


    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        TourRatingPk that = (TourRatingPk) o;

        if (!tour.equals(that.tour)) return false;
        return customerId.equals(that.customerId);

    }

    @Override
    public int hashCode() {
        int result = tour.hashCode();
        result = 31 * result + customerId.hashCode();
        return result;
    }

    @Override
    public String toString() {
        return "TourRatingPk{" +
                "tour=" + tour +
                ", customerId=" + customerId +
                '}';
    }
}

 

package com.example.ec.repo;

import com.example.ec.domain.TourRating;
import com.example.ec.domain.TourRatingPk;
import org.springframework.data.repository.CrudRepository;
import org.springframework.data.rest.core.annotation.RepositoryRestResource;

import java.util.List;
import java.util.Optional;

@RepositoryRestResource(exported = false)
public interface TourRatingRepository extends CrudRepository<TourRating, TourRatingPk> {
    List<TourRating> findByPkTourId(Integer tourId);

    Optional<TourRating> findByPkTourIdAndPkCustomerId(Integer tourId, Integer customerId);
}