Custom Cypher for Read

Defining a custom repository method

Currently you have only implemented the Spring Data’s out-of-the-box findAll(), findById(), save(), and deleteById() methods. These methods implement a standard use case for querying and saving data.

When you need something specific, you can define your own methods, and write Cypher statements that query the data and map the results back to a custom method.

For instance, the findAll() method works fine to pull the nodes in this movie graph, but what if you had a graph multiple times larger? Even at the current size, it is difficult to view all that data returned on the console. Instead, you could write a custom method to pull a random, smaller subset of the graph each time.

To modify the findAll() method you will need to:

Full code for the MovieRepository and MovieController classes is available in the dropdown below.

import org.springframework.data.neo4j.repository.Neo4jRepository;
import org.springframework.data.neo4j.repository.query.Query;

interface MovieRepository extends Neo4jRepository<Movie, String> {
    @Query("MATCH (m:Movie)<-[r:ACTED_IN]-(p:Person)" +
            "RETURN m, collect(r), collect(p) LIMIT 20;")
    Iterable<Movie> findMoviesSubset();
}

@RestController
@RequestMapping("/movies")
public class MovieController {
    private final MovieRepository movieRepo;

    public MovieController(MovieRepository movieRepo) {
        this.movieRepo = movieRepo;
    }

    @GetMapping()
    Iterable<Movie> findAllMovies() {
        return movieRepo.findMoviesSubset();
    }

    @GetMapping("/{movieId}")
    Optional<Movie> findMovieById(@PathVariable String movieId) {
        return movieRepo.findById(movieId);
    }

    @PostMapping("/save")
    Movie save(@RequestBody Movie movie) {
        return movieRepo.save(movie);
    }

    @DeleteMapping("/delete")
    void delete(@RequestParam String movieId) {
        movieRepo.deleteById(movieId);
        System.out.println("Deleted movie with movieId: " + movieId);
    }
}

Testing the findMoviesSubset() custom method

Once you make the modifications above to your project’s interface (new custom query) and controller (call findMoviesSubset()), test the new method by running the application and calling the /movies endpoint. You should see a response with a subset of movies, each with their ACTED_IN relationships and Person nodes.

curl 'localhost:8080/movies'

To take this a step further, you can define one more custom method that uses a search parameter. This will be covered in the next lesson.