java连接mongodb 1.新建一个数据库javamongotest 2.新建两个集合（user和owner），信息如下，要求：同时插入多个文档（insertMany） { "name" : “xiuxiu", "hobby" : "piano", “times”:6 } { "name" : chongyu", "hobby" : "basketball", “times”:5 } { "name" : "ruizhi", "hobby" : "books" “times”:3 }, { "name" :” yixin", "hobby" : " drawing" “times”:4 } { "name" : “yufeng", "hobby" : "music" “times”:6 } 2.向student集合插入如下文档 { "name" : “kefan", "hobby":”cloud computing”, times:1 } 3.统计文档user集合中的文档数量 4.查询name为kefan的文档，添加一个hobby属性 "likes":”helping others” 5.使用{name:"科凡"} 替换 name 为kefan 的文档 6.查询times>=5的user信息,并删除

以下是 Java 连接 MongoDB 并完成上述任务的代码：

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

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

public class MongoDBTest {
    public static void main(String[] args) {
        //连接MongoDB
        MongoClient mongoClient = new MongoClient("localhost", 27017);
        //获取数据库
        MongoDatabase db = mongoClient.getDatabase("javamongotest");
        //获取集合
        MongoCollection<Document> userCollection = db.getCollection("user");
        MongoCollection<Document> ownerCollection = db.getCollection("owner");

        //同时插入多个文档
        List<Document> userList = new ArrayList<>();
        userList.add(new Document("name", "xiuxiu").append("hobby", "piano").append("times", 6));
        userList.add(new Document("name", "chongyu").append("hobby", "basketball").append("times", 5));
        userList.add(new Document("name", "ruizhi").append("hobby", "books").append("times", 3));
        userList.add(new Document("name", "yixin").append("hobby", "drawing").append("times", 4));
        userList.add(new Document("name", "yufeng").append("hobby", "music").append("times", 6));
        userCollection.insertMany(userList);

        //向student集合插入文档
        Document studentDoc = new Document("name", "kefan").append("hobby", "cloud computing").append("times", 1);
        db.getCollection("student").insertOne(studentDoc);

        //统计文档user集合中的文档数量
        long count = userCollection.countDocuments();
        System.out.println("user集合中的文档数量为：" + count);

        //查询name为kefan的文档，添加一个hobby属性"likes":"helping others"
        Document kefanDoc = db.getCollection("student").find(Filters.eq("name", "kefan")).first();
        kefanDoc.append("likes", "helping others");
        db.getCollection("student").replaceOne(Filters.eq("name", "kefan"), kefanDoc);

        //使用{name:"科凡"}替换name为kefan的文档
        db.getCollection("student").replaceOne(Filters.eq("name", "kefan"),
                new Document("name", "科凡").append("hobby", "cloud computing").append("times", 1));

        //查询times>=5的user信息，并删除
        List<Document> userListToDelete = userCollection.find(Filters.gte("times", 5)).into(new ArrayList<>());
        for (Document doc : userListToDelete) {
            userCollection.deleteOne(doc);
        }

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

需要注意的是，上述代码需要先导入以下依赖：

<dependency>
    <groupId>org.mongodb</groupId>
    <artifactId>mongo-java-driver</artifactId>
    <version>3.12.7</version>
</dependency>