使用Java驱动程序返回null的MongoDB嵌套查询

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

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

        // 执行嵌套查询
        Document query = new Document("nestedField.field", "value");
        Document result = collection.find(query).first();

        if (result != null) {
            // 处理查询结果
            System.out.println(result.toJson());
        } else {
            System.out.println("No matching documents found.");
        }

        // 关闭数据库连接
        mongoClient.close();
    }
}