与使用Mongodb java driver 3的$objectToArray等效

import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoCursor;
import com.mongodb.client.MongoDatabase;
import org.bson.Document;

import java.util.ArrayList;
import java.util.List;

public class Main {
    public static void main(String[] args) {
        // 连接到MongoDB数据库
        MongoClient mongoClient = new MongoClient("localhost", 27017);
        MongoDatabase database = mongoClient.getDatabase("mydb");
        MongoCollection<Document> collection = database.getCollection("mycollection");

        // 查询文档
        Document document = collection.find().first();

        // 将文档字段转换为键值对的数组
        List<Document> keyValueList = new ArrayList<>();
        for (String key : document.keySet()) {
            Document keyValue = new Document();
            keyValue.append("k", key).append("v", document.get(key));
            keyValueList.add(keyValue);
        }

        // 输出结果
        for (Document keyValue : keyValueList) {
            System.out.println(keyValue.toJson());
        }

        // 关闭连接
        mongoClient.close();
    }
}