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Introduction to asynchronous DB access using Node.js and MongoDB
This document introduces asynchronous database access in Node.js using MongoDB. It discusses using callbacks for asynchronous queries instead of sequential queries. It then shows how to separate the view from the controller using a model-view-controller pattern by creating model files that encapsulate database queries. Finally, it discusses optimizing the code by initializing the database connection once and making the models and controllers rely on the initialized connection.
Introduction to asynchronous DB access using Node.js and MongoDB
- 1. Introduction to asynchronousDB access using Node.js and MongoDB Adrien Joly adrien@whyd.com
- 2. 1. Synchronous dbquery var db = DB.open("localhost:28000"); var cars = db.collection("cars"); var redCars = cars.find({color: "red"}); console.log(redCars); synchronous calls => sequential flow => simple :-)
- 3. 2. Asynchronous dbquery DB.open("localhost:28000", function(err, db) { db.collection("cars", function(err, cars) { cars.find({color: "red"}, function(err, res) { console.log(res); }); }); }); asynchronous calls => callback functions
- 4. 3. Separate viewfrom controller (MVC) db.js (model) DB.open("localhost:28000", function(err, db) { db.collection("cars", function(err, cars) { exports.getRedCars = function(callback) { cars.query({color: "red"}, callback); }); }); }); controller.js var model = require("db"); var renderRedCars = function() { model.getRedCars(function(err, redCars) { console.log(redCars); }); };
- 5. 4. Towards moremodels db.js DB.open("localhost:28000", function(err, db) { exports.getCollection = function(name, callback) { db.collection(name, callback); }; }); cars.js (model) require("db").getCollection("cars", function(err, cars) { exports.getRedCars = function(callback) { cars.query({color: "red"}, callback); }); }); }); controller.js var renderRedCars = function() { require("cars").getRedCars(function(err, redCars) { console.log(redCars); }); };
- 6. 5. Optimization, #failsafety start_server.js (main node.js application) require("db").init(function() { // start your application (->controllers->models) here }); db.js exports.init = function (initCallback) { DB.open("localhost:28000", function(err, db) { exports.getCollection = function(name, callback) { db.collection(name, callback); }; initCallback(); }); (models and controllers) ...
- 7. References required stuff http://nodejs.org/ http://www.mongodb.org/ https://github.com/christkv/node-mongodb-native about asynchronousDB access http://stackoverflow.com/questions/6275643/node-js-design-pattern-for-creating- db-connection-once invite to request :-p http://whyd.com/