spring-data-jpa-repo-creator

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.

```java
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 {
}