JAVA查询MongoDB的几种方法小结

<dependency>
    <groupId>org.mongodb</groupId>
    <artifactId>mongodb-driver-sync</artifactId>
    <version>4.4.3</version>
</dependency>

import com.mongodb.client.*;
import org.bson.Document;
public class MongoQuery {
    public static void main(String[] args) {
        // 连接MongoDB数据库
        MongoClient mongoClient = MongoClients.create("mongodb://localhost:27017");
        // 获取指定数据库和集合
        MongoDatabase database = mongoClient.getDatabase("test");
        MongoCollection<Document> collection = database.getCollection("users");
        // 查询所有age字段大于等于18的文档
        Document query = new Document("age", new Document("$gte", 18));
        FindIterable<Document> documents = collection.find(query);
        // 遍历查询结果
        for (Document document : documents) {
            System.out.println(document.toJson());
        }
        // 关闭MongoDB连接
        mongoClient.close();
    }
}

<dependency>
    <groupId>org.mongodb</groupId>
    <artifactId>mongodb-driver-reactivestreams</artifactId>
    <version>4.4.3</version>
</dependency>

<dependency>
    <groupId>org.mongodb</groupId>
    <artifactId>mongo-java-driver</artifactId>
    <version>4.4.3</version>
</dependency>

import com.mongodb.client.MongoClients;
import com.mongodb.client.MongoDatabase;
import org.bson.Document;
public class MongoCommandExample {
    public static void main(String[] args) {
        try (var client = MongoClients.create("mongodb://localhost:27017")) {
            var command = new Document("listDatabases", 1);
            var result = client.getDatabase("admin").runCommand(command);
            System.out.println(result.toJson());
        }
    }
}

import com.mongodb.MongoClient;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import com.mongodb.client.model.Filters;
import com.mongodb.client.model.Sorts;
import org.bson.Document;
import static com.mongodb.client.model.Filters.*;
import static com.mongodb.client.model.Sorts.*;
public class MongoQueryDSLExample {
    public static void main(String[] args) {
        // 创建MongoClient连接
        MongoClient mongoClient = new MongoClient("localhost", 27017);
        // 获取数据库
        MongoDatabase database = mongoClient.getDatabase("test");
        // 获取集合
        MongoCollection<Document> collection = database.getCollection("users");
        // 构建查询条件
        Document query = new Document();
        query.append("name", "张三");
        query.append("age", new Document("$gt", 18));
        // 构建排序条件
        Document sort = new Document();
        sort.append("age", 1);
        // 查询数据并排序
        collection.find(query).sort(sort).forEach(doc -> {
            System.out.println(doc.toJson());
        });
        // 关闭连接
        mongoClient.close();
    }
}