MongoDB

package at.aydin.lab.mongodb.legacy;

public record LegacyBook(String id, String title, int year) {
}

package at.aydin.lab.mongodb.modern;

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;

@Document("books")
public record BookDocument(@Id String id, String title, int year) {
}

package at.aydin.lab.mongodb.legacy;

import org.bson.Document;

// Design Pattern: Data Mapper
// Zweck: Übersetzt manuell zwischen Fachobjekt und MongoDB Document.
public final class LegacyBookMapper {
    public Document toDocument(LegacyBook b) {
        return new Document("_id", b.id()).append("title", b.title()).append("year", b.year());
    }

    public LegacyBook fromDocument(Document d) {
        return new LegacyBook(d.getString("_id"), d.getString("title"), d.getInteger("year"));
    }
}

package at.aydin.lab.mongodb.legacy;

import com.mongodb.client.MongoCollection;
import com.mongodb.client.model.ReplaceOptions;
import org.bson.Document;
import java.util.ArrayList;
import java.util.List;
import static com.mongodb.client.model.Filters.gte;

// Design Pattern: Repository
// Zweck: Mongo-Driver, BSON-Filter und manuelles Mapping werden hinter einer fachlichen API gekapselt.
public final class LegacyBookRepository {
    private final MongoCollection<Document> collection;
    private final LegacyBookMapper mapper;
    public LegacyBookRepository(MongoCollection<Document> collection, LegacyBookMapper mapper) {
        this.collection = collection;
        this.mapper = mapper;
    }

    public void save(LegacyBook book) {
        collection.replaceOne(new Document("_id", book.id()), mapper.toDocument(book), new ReplaceOptions().upsert(true));
    }

    public List<LegacyBook> findByYearGreaterThanEqual(int year) {
        List<LegacyBook> result = new ArrayList<>();
        for (Document document : collection.find(gte("year", year))) {
            result.add(mapper.fromDocument(document));
        }
        return List.copyOf(result);
    }
}

package at.aydin.lab.mongodb.modern;

import org.springframework.data.mongodb.repository.MongoRepository;
import java.util.*;

// Design Pattern: Repository
// Zweck: Query-Ableitung ersetzt manuelle Document-/Cursor-Verarbeitung.
public interface BookRepository extends MongoRepository<BookDocument, String> {
    List<BookDocument> findByYearGreaterThanEqual(int year);
}