Introduction to asynchronous DB access using Node.js and MongoDB
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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 asynchronous DB access using Node.js and MongoDB Adrien Joly [email protected]
- 2. 1. Synchronous db query 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 db query 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 view from 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 more models 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, #fail safety 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 asynchronous DB access http://stackoverflow.com/questions/6275643/node-js-design-pattern-for-creating- db-connection-once invite to request :-p http://whyd.com/