【MongoDB学习之一】初始MongoDB

环境
　　MongoDB4.0
　　win7_x64
　　CentOS6.5_x64

一、MongoDB简介
(1)MongoDB使用C++开发。
(2)MongoDB 旨在为WEB应用提供可扩展的高性能数据存储解决方案。
(3)MongoDB 将数据存储为一个文档。MongoDB是一个基于分布式文件存储的数据库。
(4)MongoDB使用BSON作为数据存储和传输的格式。BSON是一种类似JSON的二进制序列化文档，支持嵌套对象和数组。
(5)MongoDB很像MySQL，collection对应MySQL的table,document对应MySQL的row。官方给自己的定义是Key-value存储(高性能和高扩展)和传统RDBMS(丰富的查询和功能)之间的一座桥梁。

(6)MongoDB 不支持事务；

(7)MongoDB索引在内存中，而且创建受一定限制；
　　
二、安装
1、win7安装

(1)官网下载：mongodb-win32-x86_64-2008plus-ssl-4.0.11.zip
(2)解压：D:\mongoDB4.0

(3)通过服务安装，通过控制台安装：

进入目录：D:\mongoDB4.0\bin，启动cmd:

mongod --bind_ip 127.0.0.1 --logpath "D:\mongoDB4.0\log\mongodb.log" --logappend --dbpath "D:\mongoDB4.0\data\db" --port 27017 --serviceName "MongoDBService" --serviceDisplayName "MongoDB" --install

下表为mongodb启动的参数说明：

参数 描述
--bind_ip 绑定服务IP，若绑定127.0.0.1，则只能本机访问，不指定默认本地所有IP
--logpath 定MongoDB日志文件，注意是指定文件不是目录
--logappend 使用追加的方式写日志
--dbpath 指定数据库路径,注意：MongoDB默认使用db目录作为数据存储目录，但是这个目录需要手工创建，这里我们创建的是：D:\mongoDB4.0\data\db
--port 指定服务端口号，默认端口27017
--serviceName 指定服务名称
--serviceDisplayNam 指定服务名称，有多个mongodb服务时执行。
--install 指定作为一个Windows服务安装。

(4)启动服务：

启动：net start MongoDBService
停止：net stop MongoDBService

(5)MongoDB后台管理 Shell

mongo

退出：exit

参考：window平台安装 MongoDB

2、Linux安装

(1)官网下载：mongodb-linux-x86_64-4.0.12.tgz
(2)解压：

[root@node102 src]# tar -zxvf mongodb-linux-x86_64-4.0.12.tgz -C /usr/local

(3)安装：

首先创建数据目录和日志目录：

[root@node102 mongodb-linux-x86_64-4.0.12]# cd /usr/local/mongodb-linux-x86_64-4.0.12 && mkdir -p ./data/db ./log 

注意：/data/db 是 MongoDB 默认的启动的数据库路径,如果你的数据库目录不是/data/db，可以通过 --dbpath 来指定。

然后执行启动命令：

[root@node102 mongodb-linux-x86_64-4.0.12]# cd ./bin && ./mongod --dbpath=/usr/local/mongodb-linux-x86_64-4.0.12/data/db --logpath=/usr/local/mongodb-linux-x86_64-4.0.12/log/mongodb.log --fork
2019-08-09T15:30:59.686+0800 I STORAGE [main] Max cache overflow file size custom option: 0
about to fork child process, waiting until server is ready for connections.
forked process: 1492
child process started successfully, parent exiting

注意：

--fork:后台启动

(4)MongoDB后台管理 Shell,可以配置环境变量/etc/profile

[root@node102 bin]# ./mongo
MongoDB shell version v4.0.12
connecting to: mongodb://127.0.0.1:27017/?gssapiServiceName=mongodb
Implicit session: session { "id" : UUID("dd068bb5-ddaf-4709-acb4-1f5e3bd6ff40") }
MongoDB server version: 4.0.12
Welcome to the MongoDB shell.
For interactive help, type "help".
For more comprehensive documentation, see
http://docs.mongodb.org/
Questions? Try the support group
http://groups.google.com/group/mongodb-user
Server has startup warnings: 
2019-08-09T15:30:59.745+0800 I STORAGE [initandlisten] 
2019-08-09T15:30:59.745+0800 I STORAGE [initandlisten] ** WARNING: Using the XFS filesystem is strongly recommended with the WiredTiger storage engine
2019-08-09T15:30:59.745+0800 I STORAGE [initandlisten] ** See http://dochub.mongodb.org/core/prodnotes-filesystem
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] 
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] ** WARNING: Access control is not enabled for the database.
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] ** Read and write access to data and configuration is unrestricted.
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] ** WARNING: You are running this process as the root user, which is not recommended.
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] 
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] ** WARNING: This server is bound to localhost.
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] ** Remote systems will be unable to connect to this server. 
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] ** Start the server with --bind_ip <address> to specify which IP 
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] ** addresses it should serve responses from, or with --bind_ip_all to
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] ** bind to all interfaces. If this behavior is desired, start the
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] ** server with --bind_ip 127.0.0.1 to disable this warning.
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] 
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] 
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/enabled is 'always'.
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] ** We suggest setting it to 'never'
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] 
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'.
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] ** We suggest setting it to 'never'
2019-08-09T15:31:00.463+0800 I CONTROL [initandlisten] 
> 2+2
4
> exit
bye
[root@node102 bin]#

(5)关闭

(5.1)在mongo客户端关闭

> use admin
> db.shutdownServer()

(5.2)使用mongod，注意关闭哪个数据库 需要指定对应的--dbpath

[root@node102 bin]# ./mongod --dbpath=/usr/local/mongodb-linux-x86_64-4.0.12/data/db --shutdown

参考：Linux平台安装MongoDB

注意：mongoDB4好像不再支持web用户界面。

三、MongoDB存取原理
内部执行引擎为JS解释器（解释符合JS语法的语句）：
插入操作：把JSON对象数据存储成BSON结构的文档结构，
查询操作：把BSON结构数据转换为JSON对象.

四、MongoDB和关系型数据库区别

参考：MongoDB 概念解析

package com.mongodb;

import java.util.HashMap;
import java.util.Map;

import org.bson.Document;
import org.bson.conversions.Bson;
import org.bson.types.ObjectId;

import com.mongodb.client.FindIterable;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoCursor;
import com.mongodb.client.MongoDatabase;

public class TestMongoDB {

    public static void main(String[] args) 
    {
        TestMongoDB test = new TestMongoDB();
        //插入数据
        test.insertData();
        //查询数据
        test.find();
        test.findone();
        //更新数据
        test.update();
        //删除数据
        test.delete();
    }
    
    public void find()
    {
        //创建连接客户端
                MongoClient client = new MongoClient("localhost",27017);
                //获取数据库对象
                MongoDatabase db = client.getDatabase("test");
                //获取操作的集合对象
                MongoCollection<Document> collection = db.getCollection("wjy");
                //具体操作
                FindIterable<Document> it = collection.find();
                //获取游标对象
                MongoCursor<Document> cursor = it.iterator();
                while (cursor.hasNext())
                {
                    //取出每一个文档对象（行）
                    Document doc = cursor.next();
                    String name = doc.getString("name");
                    if ("乔峰".equals(name))
                    {
                        Integer age = doc.getInteger("age");
                        System.out.println(name+","+age);
                    }
                    else
                    {
                        Double age = doc.getDouble("age");
                        System.out.println(name+","+age);
                    }
                    
                }
                //释放资源
                cursor.close();
                client.close();
    }
    
    public void findone()
    {
        MongoClient client = new MongoClient("localhost",27017);
        //获取数据库对象
        MongoDatabase db = client.getDatabase("test");
        //获取操作的集合对象
        MongoCollection<Document> collection = db.getCollection("wjy");
        //具体操作
        Bson filter = new BasicDBObject("_id", new ObjectId("5850eacd7065f52b0eab7ff4"));
        FindIterable<Document> it = collection.find(filter);
        //获取游标对象
        MongoCursor<Document> cursor = it.iterator();
        while (cursor.hasNext())
        {
            //取出每一个文档对象（行）
            Document doc = cursor.next();
            String name = doc.getString("name");
            if ("乔峰".equals(name))
            {
                Integer age = doc.getInteger("age");
                System.out.println(name+","+age);
            }
            else
            {
                Double age = doc.getDouble("age");
                System.out.println(name+","+age);
            }
            
        }
        //释放资源
        cursor.close();
        client.close();
    }
    
    public void insertData()
    {
        MongoClient client = new MongoClient("localhost",27017);
        MongoDatabase db = client.getDatabase("test");
        MongoCollection<Document> collection = db.getCollection("wjy");
        //使用Map来封装json数据
        Map<String,Object> map = new HashMap<String,Object>();
        map.put("name", "乔峰");
        map.put("age", 35);
        map.put("gender", "true man");
        Map<String,Object> hobbyMap = new HashMap<String,Object>();
        hobbyMap.put("girl", "阿朱");
        hobbyMap.put("gongfu", "降龙十八掌");
        map.put("hobby", hobbyMap);
        Document doc = new Document(map);
        
        collection.insertOne(doc);
        
        client.close();
    }
    
    public void update()
    {
        MongoClient client = new MongoClient("localhost",27017);
        MongoDatabase db = client.getDatabase("test");
        MongoCollection<Document> collection = db.getCollection("wjy");
        
        Bson filter = new BasicDBObject("_id",new ObjectId("5850eacd7065f52b0eab7ff4"));
        
        Map<String,Object> map = new HashMap<String,Object>();
        map.put("name", "张无忌");
        map.put("age", 35);
        Bson update = new BasicDBObject(map);
        
        collection.updateOne(filter, new BasicDBObject("$set",update));
        
        client.close();
    }
    public void delete()
    {
        MongoClient client = new MongoClient("localhost",27017);
        MongoDatabase db = client.getDatabase("test");
        MongoCollection<Document> collection = db.getCollection("wjy");
        
        collection.deleteOne(new BasicDBObject("_id",new ObjectId("5850eacd7065f52b0eab7ff4")));
        
        client.close();
    }
}

参考：
官方网站：http://www.mongodb.org/
MongoDB教程：https://www.w3cschool.cn/mongodb/mongodb-intro.html