java中的Mongo regex查询

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

public class MongoRegexQueryExample {
    public static void main(String[] args) {
        // 创建 MongoClient 实例
        MongoClient mongoClient = MongoClients.create("mongodb://localhost:27017");

        // 获取数据库和集合
        MongoDatabase database = mongoClient.getDatabase("testdb");
        MongoCollection<Document> collection = database.getCollection("testcollection");

        // 定义正则表达式查询条件
        String pattern = "^J.*"; // 匹配以 "J" 开头的字符串
        Document query = new Document("name", new Document("$regex", pattern));

        // 执行查询并打印结果
        for (Document doc : collection.find(query)) {
            System.out.println(doc.toJson());
        }

        // 关闭 MongoClient
        mongoClient.close();
    }
}