morphia和如何更新现有文档字段

@Entity("documents")
public class Document {
    @Id
    private String _id;
    private String title;
    private String content;

    // 构造方法、getter 和 setter 方法
}

@Entity("collections")
public class Collection {
    @Id
    private String _id;
    private List<Document> documents;

    // 构造方法、getter 和 setter 方法
}

@Entity("users")
public class User {
    @Id
    private String _id;
    private String name;
    private String email;
    private Collection<Document> documents;

    // 构造方法、getter 和 setter 方法
}

import com.mongodb.client.model.Filters;
import org.bson.Document;
import org.bson.conversions.Bson;

import java.util.List;

// ...

public void updateDocument(String database, String collection, String id, String title, String content) {
    Bson update = Aggregates.updateOne(
        Aggregates.match(Filters.eq("_id", id)),
        Aggregates.set("title", title),
        Aggregates.set("content", content)
    );

    MongoDatabase database = getDatabase();
    MongoCollection<Document> collection = database.getCollection(collection);

    List<Document> results = collection.updateOne(Filters.eq("_id", id), update).getModifiedResults();
}

public void updateFields(String database, String collection, String id, String title, String content) {
    Bson update = Aggregates.updateOne(
        Aggregates.match(Filters.eq("_id", id)),
        Aggregates.set("title", title),
        Aggregates.set("content", content)
    );

    MongoDatabase database = getDatabase();
    MongoCollection<Document> collection = database.getCollection(collection);

    List<Document> results = collection.updateOne(Filters.eq("_id", id), update).getModifiedResults();
}