一、Java 实现对 MongDB 的操作

1、前提条件

除了通过启动 mongo 进程进如 Shell 环境访问数据库外，MongoDB 还提供了其他基于编程语言的访问数据库方法。MongoDB 官方提供了 Java 语言的驱动包，利用这些驱动包可使用多种编程方法来连接并操作 MongoDB 数据库。

想要在 Java 程序中使用 MongoDB，需要确保您的电脑上已经安装了 MongoDB，并搭建好了 Java 的环境。

2、添加依赖

在 Maven 中添加以下依赖来使用操作 MongoDB 数据库：

    <dependencies>
        <dependency>
            <groupId>org.mongodb</groupId>
            <artifactId>bson</artifactId>
            <version>3.12.11</version>
        </dependency>
        <dependency>
            <groupId>org.mongodb</groupId>
            <artifactId>mongodb-driver</artifactId>
            <version>3.12.11</version>
        </dependency>
        <dependency>
            <groupId>org.mongodb</groupId>
            <artifactId>mongodb-driver-core</artifactId>
            <version>3.12.11</version>
        </dependency>
       
        ...
    </dependencies>

二、Java 操作 MongoDB 数据库 Demo

1、连接数据库

package com.db.demo;

import com.mongodb.client.MongoDatabase;
import com.mongodb.MongoClient;
import com.mongodb.MongoCredential;

/**
 * @version 1.0.0
 * @description 连接数据库
 **/
public class ConnectToMongodb {

    public static void main(String[] args) {
        // 创建 MongoDB 连接
        MongoClient mongo = new MongoClient("localhost", 27017);

        // 连接到 MongoDB
        MongoCredential credential = MongoCredential.createCredential("study", "study", "password".toCharArray());
        System.out.println("Credentials ::" + credential);

        // 访问数据库
        MongoDatabase database = mongo.getDatabase("study");
        System.out.println("Connect to database successfully!");
        System.out.println("MongoDatabase info is : " + database.getName());
    }
}

运行 Main 函数，返回以下结果：

Credentials ::MongoCredential{mechanism=null, userName=‘study’, source=‘study’, password=, mechanismProperties=}
Connect to database successfully!
MongoDatabase info is : study

2、创建集合

package com.db.demo;

import com.mongodb.client.MongoDatabase;
import com.mongodb.MongoClient;
import com.mongodb.MongoCredential;

/**
 * @version 1.0.0
 * @description 创建集合
 **/
public class CreatingCollection {
    public static void main(String[] args) {
        // 创建 MongoDB 连接
        MongoClient mongo = new MongoClient("localhost", 27017);

        // 连接到 MongoDB
        MongoCredential credential = MongoCredential.createCredential("study", "study", "password".toCharArray());
        System.out.println("Credentials ::" + credential);

        // 访问数据库
        MongoDatabase database = mongo.getDatabase("study");
        System.out.println("Connect to database successfully!");
        System.out.println("MongoDatabase info is : " + database.getName());

        // 创建集合
        database.createCollection("study_test_3");
        System.out.println("create collection successfully!");
    }
}

运行 Main 函数，返回以下结果：

Credentials ::MongoCredential{mechanism=null, userName=‘study’, source=‘study’, password=, mechanismProperties=}
Connect to database successfully!
MongoDatabase info is : study

create collection successfully!

3、列出所有集合

 public static void main(String[] args) {
        // 创建 MongoDB 连接
        MongoClient mongo = new MongoClient("localhost", 27017);

        // 连接到 MongoDB
        MongoCredential credential = MongoCredential.createCredential("study", "study", "password".toCharArray());
        System.out.println("Credentials ::" + credential);

        // 访问数据库
        MongoDatabase database = mongo.getDatabase("study");
        System.out.println("Connect to database successfully!");
        System.out.println("MongoDatabase info is : " + database.getName());

        // 检索集合列表
        for (String name : database.listCollectionNames()) {
            System.out.println(name);
        }
    }

运行 Main 函数，返回以下结果：

Credentials ::MongoCredential{mechanism=null, userName=‘study’, source=‘study’, password=, mechanismProperties=}
Connect to database successfully!
MongoDatabase info is : study

study
study_test_3
study_test_2

4、获取/选择集合

.....
// 创建集合
MongoCollection<Document> collection = database.getCollection("study");
System.out.println("chose collection : " + collection.getNamespace());
.....

运行 Main 函数，返回以下结果：

chose collection : study.study

5、插入文档

public static void main(String[] args) {
        // 创建 MongoDB 连接
        MongoClient mongo = new MongoClient("localhost", 27017);

        // 连接到 MongoDB
        MongoCredential credential = MongoCredential.createCredential("study", "study", "password".toCharArray());
        System.out.println("Credentials ::" + credential);

        // 访问数据库
        MongoDatabase database = mongo.getDatabase("study");
        System.out.println("Connect to database successfully!");
        System.out.println("MongoDatabase info is : " + database.getName());

        // 检索集合
        MongoCollection<Document> collection = database.getCollection("study");
        System.out.println("chose collection : " + collection.getNamespace());

        Document document = new Document("title", "MongoDB")
                .append("description", "database")
                .append("likes", 200)
                .append("url", "https://study.xxx.xx/")
                .append("by", "study");

        // 将文档插入到集合中
        collection.insertOne(document);
        System.out.println("Document insert successfully!");
    }

运行 Main 函数，返回以下结果：

Credentials ::MongoCredential{mechanism=null, userName=‘study’, source=‘study’, password=, mechanismProperties=}
Connect to database successfully!
MongoDatabase info is : study
chose collection : study.study

Document insert successfully!

6、查询文档

....
// 获取 iterable 对象
FindIterable<Document> iterDoc = collection.find();
int i = 1;
// 获取迭代器
for (Document document : iterDoc) {
  System.out.println(document);
  i++;
}
.......

7、更新文档

.....
// 更新单个可用 updateOne
collection.updateMany(Filters.eq("title", "MongoDB"), Updates.set("likes", 150));
System.out.println("Document update successfully...");
// 更新后检索文档
// 获取 iterable 对象
FindIterable<Document> iterDoc = collection.find();
int i = 1;
// 获取迭代器
for (Document document : iterDoc) {
  System.out.println(document);
  i++;
}
......

8、删除文档

......
// 删除文档 删除多个可用 deleteMany
collection.deleteOne(Filters.eq("title", "MongoDB"));
System.out.println("Document delete successfully...");
// 删除后检索文档
// 获取 iterable 对象
FindIterable<Document> iterDoc = collection.find();
int i = 1;
// 获取迭代器
for (Document document : iterDoc) {
  System.out.println(document);
  i++;
}
......

9、删除集合

......
// 删除集合
collection.drop();
System.out.println("drop collection : " + collection.getNamespace());
.....