MongoDB学习（2）—Node.js与MongoDB的基本连接示例
前提已经安装了node.js和MongoDB，本文使用的node.js是v0.12.0，MongoDB是3.0.0。
初始化数据
启动MongoDB服务，在test数据库中插入一条实例数据：
db.user.install({name:"scaleworld",age:27});
在Node.js中引入MongoDB模块
npm install mongodb
编写mongodbDemo.js
var mongodb = require('mongodb');
var server = new mongodb.Server("localhost",27017,{safe:true});
new mongodb.Db('test',server,{}).open(function(error,client){
if(error) throw error;
var collection = new mongodb.Collection(client,'user');
collection.find(function(error,cursor){
cursor.each(function(error,doc){
if(doc){
console.log("name:"+doc.name+" age:"+doc.age);
}
});
});
});
运行
{ code: 'MODULE_NOT_FOUND' }
js-bson: Failed to load c++ bson extension, using pure JS version
================================================================================
Please ensure that you set the default write concern for the database by setting =
= one of the options =
= =
= w: (value of > -1 or the string 'majority'), where < 1 means =
= no write acknowlegement =
= journal: true/false, wait for flush to journal before acknowlegement =
= fsync: true/false, wait for flush to file system before acknowlegement =
= =
=For backward compatibility safe is still supported and =
= allows values of =
= the default value is false which means the driver receives does not =
= return the information of the success/error of the insert/update/remove =
= =
= ex: new Db(new Server('localhost', 27017), {safe:false}) =
= =
= http://www.mongodb.org/display/DOCS/getLastError+Command =
= =
=The default of no acknowlegement will change in the very near future =
= =
=This message will disappear when the default safe is set on the driver Db =
========================================================================================
name:scaleworld age:27
虽然最后打印出了我们之前插入的数据，但是前面一大串的错误还是人看着不舒服，我们要消灭它们。
Error: Cannot find module '../build/Release/bson'的解决办法
{ code: 'MODULE_NOT_FOUND' }
js-bson: Failed to load c++ bson extension, using pure JS version
头两行说的是没有发现bson模块。好办我们立马安装：
npm install bson
然后将D:\nodejsdemo\node_modules\mongodb\node_modules\bson\ext\index.js中的bson = require('../build/Release/bson')改成bson = require('bson') ，重新运行。
不过这样只是解决头两行的问题，还有用=包围起来的问题。
“Please ensure that you set the default write concern for the database”的解决办法
从最后一句话“This message will disappear when the default safe is set on the driver Db”我们就可以看出该问题的解决办法，只要将数据库连接设置为安全即可。
具体代码修改如下：
new mongodb.Db('test',server,{})修改为new mongodb.Db('test',server,{safe:true})
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