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
{ [Error: Cannot find module '../build/Release/bson'] 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 [true | false | {j:true} | {w:n, wtimeout:n} | {fsync:true}] = = 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
{ [Error: Cannot find module '../build/Release/bson'] 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 })
正文到此结束
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