Spring Data JPA Repository Creator

Instructions

The following are key principles to follow while creating Spring Data JPA Repositories:

• Make sure to create the recommended package structure for Spring Boot projects
• Create repositories only for aggregate roots
• Use @Query with JPQL for custom queries
• Prefer meaningful method names over long Spring Data JPA finder methods
• Use constructor expressions or Projections for read operations
• Use default methods for convenience operations

Example: EventRepository

File: events/domain/EventRepository.java

interface EventRepository extends JpaRepository<EventEntity, EventId> {

    @Query("""
            SELECT e FROM EventEntity e
            WHERE e.startDatetime > :now
            ORDER BY e.startDatetime ASC
            """)
    List<EventEntity> findUpcomingEvents(@Param("now") Instant now);

    @Query("""
            SELECT e FROM EventEntity e
            WHERE e.code = :code
            """)
    Optional<EventEntity> findByCode(@Param("code") EventCode code);

    // Convenience methods using default interface methods
    default EventEntity getByCode(EventCode eventCode) {
        return this.findByCode(eventCode)
                .orElseThrow(() -> new ResourceNotFoundException("Event not found with code: " + eventCode));
    }
}

Enable JPA Auditing

Enable JPA Auditing support to automatically populate createdAt and updatedAt fields.

• Add @CreatedDate and @LastModifiedDate annotations to your BaseEntity class.
• Add @EntityListeners(AuditingEntityListener.class) to your BaseEntity class.
• Create a Spring @Configuration class and add @EnableJpaAuditing annotation.

package dev.sivalabs.meetup4j.shared;

import jakarta.persistence.Column;
import jakarta.persistence.EntityListeners;
import jakarta.persistence.MappedSuperclass;
import org.springframework.data.annotation.CreatedDate;
import org.springframework.data.annotation.LastModifiedDate;
import org.springframework.data.jpa.domain.support.AuditingEntityListener;

import java.time.Instant;

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

    @Column(name = "created_at", nullable = false, updatable = false)
    @CreatedDate
    protected Instant createdAt;

    @Column(name = "updated_at", nullable = false)
    @LastModifiedDate
    protected Instant updatedAt;

    // Getters and setters
}

Enable JPA Auditing in your application configuration:

@Configuration
@EnableJpaAuditing
public class JpaConfig {
}