使用Nodejs连接mongodb数据库的实现

一个简单的nodejs连接mongodb示例，来自 mongodb官方示例

1. 创建package.json

首先，创建我们的工程目录connect-mongodb，并作为我们的当前目录

mkdir connect-mongodb
cd connect-mongodb

输入npm init命令创建package.json

npm init

然后，安装mongodb的nodejs版本driver

npm install mongodb --save

mongodb驱动包将会安装到当前目录下的node_modules中

2. 启动MongoDB服务器

安装MongoDB并启动MongoDB数据库服务，可参考我之前的文章，或者MongoDB官方文档

3. 连接MongoDB

创建一个app.js文件，并添加以下代码来连接服务器地址为192.168.0.243，mongodb端口为27017上名称为myNewDatabase的数据库

var MongoClient = require('mongodb').MongoClient,
 assert = require('assert');
// Connection URL
var url = 'mongodb://192.168.0.243:27017/myNewDatabase';
MongoClient.connect(url,function(err,db){
 assert.equal(null,err);
 console.log("Connection successfully to server");
 db.close();
});

在命令行输入以下命令运行app.js

node app.js

4. 插入文档

在app.js中添加以下代码，使用insertMany方法添加3个文档到documents集合中

var insertDocuments = function(db, callback){
 // get ths documents collection
 var collection = db.collection('documents');
 // insert some documents
 collection.insertMany([
 {a:1},{a:2},{a:3}
 ],function(err,result){
 assert.equal(err,null);
 assert.equal(3,result.result.n);
 assert.equal(3,result.ops.length);
 console.log("Inserted 3 documents into the collection");
 callback(result);
 });
};

insert命令返回一个包含以下属性的对象:

在app.js更新以下代码调用insertDocuments方法

var MongoClient = require('mongodb').MongoClient
 , assert = require('assert');
// Connection URL
var url = 'mongodb://localhost:27017/myproject';
// Use connect method to connect to the server
MongoClient.connect(url, function(err, db) {
 assert.equal(null, err);
 console.log("Connected successfully to server");
 insertDocuments(db, function() {
 db.close();
 });
});

在命令行中使用node app.js运行

5. 查询所有文档

添加findDocuments函数

var findDocuments = function(db,callback){
 // get the documents collection
 var collection = db.collection('documents');
 // find some documents
 collection.find({}).toArray(function(err,docs){
 assert.equal(err,null);
 console.log("Found the following records");
 console.log(docs);
 callback(docs);
 });
};

findDocuments函数查询了所有'documents'集合中所有的文档，将此函数添加到MongoClient.connect的回调函数中

var MongoClient = require('mongodb').MongoClient
 , assert = require('assert');
// Connection URL
var url = 'mongodb://localhost:27017/myproject';
// Use connect method to connect to the server
MongoClient.connect(url, function(err, db) {
 assert.equal(null, err);
 console.log("Connected correctly to server");
 insertDocuments(db, function() {
 findDocuments(db, function() {
 db.close();
 });
 });
});

6. 使用过滤条件(query filter)查询文档

查询'a':3的文档

var findDocuments = function(db, callback) {
 // Get the documents collection
 var collection = db.collection('documents');
 // Find some documents
 collection.find({'a': 3}).toArray(function(err, docs) {
 assert.equal(err, null);
 console.log("Found the following records");
 console.log(docs);
 callback(docs);
 }); 
}

7. 更新文档

var updateDocument = function(db,callback){
 // get the documents collection
 var collection = db.collection('documents');
 // update document where a is 2, set b equal to 1
 collection.updateOne({a:2},{
 $set:{b:1}
 },function(err,result){
 assert.equal(err,null);
 assert.equal(1,result.result.n);
 console.log("updated the document with the field a equal to 2");
 callback(result);
 });
};

updateDocument方法更新满足条件a为2的第一个文档，新增一个b属性，并将其设置为1。

将updateDocument方法添加到MongoClient.connect方法的回调中

MongoClient.connect(url,function(err,db){
 assert.equal(null,err);
 console.log("Connection successfully to server");
 insertDocuments(db,function(){
 updateDocument(db,function(){
 db.close();
 });
 });
});

8. 删除文档

var removeDocument = function(db,callback){
 // get the documents collection
 var collection = db.collection('documents');
 // remove some documents
 collection.deleteOne({a:3},function(err,result){
 assert.equal(err,null);
 assert.equal(1,result.result.n);
 console.log("removed the document with the field a equal to 3");
 callback(result);
 });
};

添加到app.js中

var MongoClient = require('mongodb').MongoClient
 , assert = require('assert');
// Connection URL
var url = 'mongodb://localhost:27017/myproject';
// Use connect method to connect to the server
MongoClient.connect(url, function(err, db) {
 assert.equal(null, err);
 console.log("Connected successfully to server");
 insertDocuments(db, function() {
 updateDocument(db, function() {
 removeDocument(db, function() {
 db.close();
 });
 });
 });
});

9. 创建索引

索引能够改善应用的性能。下面你代码在'a'属性上添加索引

var indexCollection = function(db,callback){
 db.collection('documents').createIndex({
 a:1
 },null,function(err,results){
 console.log(results);
 callback();
 });
};

更新app.js

MongoClient.connect(url,function(err,db){
 assert.equal(null,err);
 console.log("Connection successfully to server");
 insertDocuments(db,function(){
 indexCollection(db,function(){
 db.close();
 });
 });
});