✅ Spring Data’s Unified Data Access

Spring Data JPA offers a consistent and powerful API for accessing and querying data. Once your repositories are configured, you can take advantage of advanced capabilities like:

  1. Sorting
  2. Pagination
  3. DTO-based Projections
  4. Dynamic Queries (via @Query)
  5. Optional: Specifications / Query by Example (QBE)

This section builds on your existing CrudRepository and JpaRepository interfaces using real examples from the Movie-Actor-Studio model.

📌 1. Sorting Results

Spring Data allows you to pass a Sort parameter directly into query methods:

```java
public interface MovieRepository2 extends PagingAndSortingRepository<Movie, Long> {

    List<Movie> findByGenre(String genre, Sort sort);
}

Sort sort = Sort.by(Sort.Direction.DESC, "releaseDate");
List<Movie> movies = movieRepository2.findByGenre("Sci-Fi", sort);```

📌 2. Pagination Support

You can use PagingAndSortingRepository or extend JpaRepository to get pagination:

public interface MovieRepository2 extends PagingAndSortingRepository<Movie, Long> {

    Page<Movie> findByGenre(String genre, Pageable pageable);
}

Example Usage

Pageable pageable = PageRequest.of(0, 5, Sort.by("releaseDate").descending());
Page<Movie> page = movieRepository2.findByGenre("Action", pageable);
List<Movie> movies = page.getContent();

✅ Pageable and Page work seamlessly with Spring MVC controllers as well.

📌 3. Projections with DTOs

You can fetch flattened data using DTO projections, either via JPQL or Spring Data’s interface-based projection mechanism.

DTO Class

package com.nicordesigns.dto;

public class MovieSummaryDTO2 {
    private String title;
    private String studioName;

    public MovieSummaryDTO2(String title, String studioName) {
        this.title = title;
        this.studioName = studioName;
    }

    public String getTitle() { return title; }
    public String getStudioName() { return studioName; }
}

JPQL-based Projection

@Query("SELECT new com.nicordesigns.dto.MovieSummaryDTO2(m.title, m.studio.studioName) FROM Movie m")
List<MovieSummaryDTO2> fetchMovieSummaries();

📌 4. Custom JPQL & Native Queries

You’re not limited to derived method names. You can write expressive JPQL or even native SQL if needed:

@Query("SELECT new com.nicordesigns.dto.MovieSummaryDTO2(m.title, m.studio.studioName) FROM Movie m")
List<MovieSummaryDTO2> fetchMovieSummaries();

📌 5. Optional: Query by Example (QBE)

For dynamic filter criteria, QBE can be powerful:

Example<Movie> example = Example.of(new Movie(null, "Avatar", null, 0, null, null, null, null));
List<Movie> results = movieRepository2.findAll(example);

✅ Summary

Spring Data’s unified approach gives you: