Unlocking Semantic Search: Building a Java-Powered Movie Search Engine with Atlas Vector Search and Spring Boot

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{
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  "fields": [{
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    "type": "vector",
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    "path": "plot_embedding",
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    "numDimensions": 1536,
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    "similarity": "euclidean"
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  }]
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}

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<mongodb.version>4.11.0</mongodb.version>

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public class Movie {
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    @BsonProperty("_id")
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    private ObjectId Id;
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    private String title;
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    private int year;
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    private int runtime;
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    private Date released;
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    private String poster;
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    private String plot;
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    private String fullplot;
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    private String lastupdated;
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    private String type;
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    private List<String> directors;
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    private Imdb imdb;
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    private List<String> cast;
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    private List<String> countries;
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    private List<String> genres;
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    private Tomatoes tomatoes;
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    private int num_mflix_comments;
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    private String plot_embeddings;
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    // Getters and setters for Movie fields
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}

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public static class Imdb {
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    private double rating;
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    private int votes;
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    private int id;
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    // Getters and setters for Imdb fields
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}

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public static class Tomatoes {
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    private Viewer viewer;
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    private Date lastUpdated;
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    // Getters and setters for Tomatoes fields
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}

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public static class Viewer {
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    private double rating;
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    private int numReviews; 
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    // Getters and setters for Viewer fields
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}

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mongodb.uri=mongodb+srv://<username>:<password>@<cluster>.mongodb.net/
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mongodb.database=sample_mflix

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@Configuration
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public class MongodbConfig {
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    @Value("${mongodb.uri}")
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    private String MONGODB_URI;
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    @Value("${mongodb.database}")
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    private String MONGODB_DATABASE;

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    @Bean
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    public MongoClient mongoClient() {
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        CodecRegistry pojoCodecRegistry = CodecRegistries.fromRegistries(
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            MongoClientSettings.getDefaultCodecRegistry(),
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            CodecRegistries.fromProviders(
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                PojoCodecProvider.builder().automatic(true).build()
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            )
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        );
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        MongoClientSettings settings = MongoClientSettings.builder()
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            .applyConnectionString(new ConnectionString(MONGODB_URI))
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            .codecRegistry(pojoCodecRegistry)
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            .build();
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        return MongoClients.create(settings);
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    }

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    @Bean
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    public MongoDatabase mongoDatabase(MongoClient mongoClient) {
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        return mongoClient.getDatabase(MONGODB_DATABASE); 
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    }
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}

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@Service
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public class OpenAIService {
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	private static final String OPENAI_API_URL = "https://api.openai.com";
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	@Value("${openai.api.key}")
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	private String OPENAI_API_KEY;
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	private WebClient webClient;
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	@PostConstruct
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	void init() {
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		this.webClient = WebClient.builder()
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			.clientConnector(new ReactorClientHttpConnector())
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			.baseUrl(OPENAI_API_URL)
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			.defaultHeader("Content-Type", MediaType.APPLICATION_JSON_VALUE)
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			.defaultHeader("Authorization", "Bearer " + OPENAI_API_KEY)
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			.build();
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	}
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	public Mono<List<Double>> createEmbedding(String text) {
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	Map<String, Object> body = Map.of(
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		"model", "text-embedding-ada-002",
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		"input", text
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	);
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	return webClient.post()
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		.uri("/v1/embeddings")
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		.bodyValue(body)
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		.retrieve()
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		.bodyToMono(EmbeddingResponse.class)
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		.map(EmbeddingResponse::getEmbedding);
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	}
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}

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public class EmbeddingData {
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	private List<Double> embedding;
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	public List<Double> getEmbedding() {
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		return embedding;
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	}
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	public void setEmbedding(List<Double> embedding) {
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		this.embedding = embedding;
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	}
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}

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public class EmbeddingResponse {
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	private List<EmbeddingData> data;
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	public List<Double> getEmbedding() {
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		return data.get(0).getEmbedding();
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	}
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	public List<EmbeddingData> getData() {
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		return data;
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	}
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	public void setData(List<EmbeddingData> data) {
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		this.data = data;
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	}
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}

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public interface MovieRepository {
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    Flux<Movie> findMoviesByVector(List<Double> embedding);
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}

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@Repository
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public class MovieRepositoryImpl implements MovieRepository {
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    private final MongoDatabase mongoDatabase;
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    public MovieRepositoryImpl(MongoDatabase mongoDatabase) {
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        this.mongoDatabase = mongoDatabase;
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    }
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    private MongoCollection<Movie> getMovieCollection() {
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        return mongoDatabase.getCollection("embedded_movies", Movie.class);
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    }
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    @Override
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    public Flux<Movie> findMoviesByVector(List<Double> embedding) {
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        String indexName = "PlotVectorSearch";
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        int numCandidates = 100;
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        int limit = 5;
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        List<Bson> pipeline = asList(
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            vectorSearch(
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                fieldPath("plot_embedding"),
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                embedding,
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                indexName,
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                numCandidates,
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                limit));
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        return Flux.from(getMovieCollection().aggregate(pipeline, Movie.class));
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    }
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}

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@Service
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public class MovieService {
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    private final MovieRepository movieRepository;
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    private final OpenAIService embedder;
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    @Autowired
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    public MovieService(MovieRepository movieRepository, OpenAIService embedder) {
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        this.movieRepository = movieRepository;
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        this.embedder = embedder;
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    }
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    public Mono<List<Movie>> getMoviesSemanticSearch(String plotDescription) {
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        return embedder.createEmbedding(plotDescription)
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                .flatMapMany(movieRepository::findMoviesByVector)
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                .collectList();
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    }
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}

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@RestController
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public class MovieController {
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	private final MovieService movieService;
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	@Autowired
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	public MovieController(MovieService movieService) {
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		this.movieService = movieService;
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	}
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	@GetMapping("/movies/semantic-search")
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	public Mono<List<Movie>> performSemanticSearch(@RequestParam("plotDescription") String plotDescription) {
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		return movieService.getMoviesSemanticSearch(plotDescription);
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	}
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}

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curl -X GET "http://localhost:8080/movies/semantic-search?plotDescription=A%20cop%20from%20china%20and%20cop%20from%20america%20save%20kidnapped%20girl"

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Movie title: Rush Hour
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Plot: Two cops team up to get back a kidnapped daughter.
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Movie title: Police Story 3: Supercop
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Plot: A Hong Kong detective teams up with his female Red Chinese counterpart to stop a Chinese drug czar.
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Movie title: Fuk sing go jiu
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Plot: Two Hong-Kong cops are sent to Tokyo to catch an ex-cop who stole a large amount of money in diamonds. After one is captured by the Ninja-gang protecting the rogue cop, the other one gets ...
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Movie title: Motorway
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Plot: A rookie cop takes on a veteran escape driver in a death defying final showdown on the streets of Hong Kong.
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Movie title: The Corruptor
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Plot: With the aid from a NYC policeman, a top immigrant cop tries to stop drug-trafficking and corruption by immigrant Chinese Triads, but things complicate when the Triads try to bribe the policeman.