webinar: get started with the mean stack
TRANSCRIPT
Developing a Basic REST API from Scratch Using TDD
Valeri KarpovNode.js Engineer, MongoDBwww.thecodebarbarian.com
github.com/vkarpov15@code_barbarian
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What is this talk about?
•MongoDB is great for storing web/mobile app data•So let’s build a REST API using Node.js!•+ learn a bit about test-driven dev with Node.js•+ learn two MongoDB schema design principles•Server-side only - just JSON, no HTML•No AngularJS part, focus more on MongoDB•Upcoming EdX course
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Overview
•Part 1: Shopping Cart Application–Search for products–Add them to your cart–Check out with Stripe
•Part 2: Using the Mongoose ODM•Part 3: Schema Design•Part 4: Building an API with the Express framework•Part 5: Testing with Mocha + Superagent
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Part 1: What Does the App Do?
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What Does the App Do?
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What Does the App Do?
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App Structure
•"Bad programmers worry about the code. Good programmers worry about data structures and their relationships." - Linus Torvalds•3 schemas for 3 collections:•Products•Categories•Users
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Schema Relationships
•Product belongs to one or more categories•Users can have multiple products in their cart•Representing relationships in MongoDB is tricky•But that’s what mongoose is for
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Part 2: Using the Mongoose ODM•“Object document mapper” (like ORM, but for MongoDB)•“MongoDB object modeling designed to work in an asynchronous environment”•Written for Node.js•Provides schema validation, pseudo-JOINs, etc.
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Brief Overview of Node.js
•require()
•Async I/O
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What Does Async Mean?
Register eventhandler
In node.js, you don’t execute I/O imperatively.You register a callback to execute when the I/O is done
Prints before“done reading”
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Using Your Schema
Create User
Save user to MongoDB
Load user from MongoDB
Print user to stdout
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Part 2 Takeaways
•Mongoose provides several neat features–Model part of MVC–Default values–Schema validation and declarative schema design
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Part 3: Schema Design
•3 schemas:–Product–Category–User
•Going to use mongoose to define schemas•Will use a couple key schema design principles
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Product Schema
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Product Schema in Action
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Category Schema
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Category Schema Queries
•What categories are descendants of “Electronics”?•
•What categories are children of “Non-Fiction”?• •What categories are ancestors of “Phones”?
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Product + Category Schemas
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Category Schema Takeaways
•Queries in MongoDB should be simple•Strive for minimal data transformation by server•“Store what you query for”•“If you need [the aggregation framework in a heavily used API endpoint], you're screwed anyway, and should fix your program.” - Linus Torvalds•Good for performance and developer sanity
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User Schema
User’s cart as an arrayof ObjectIds...
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Principle of Least Cardinality
•Product and user = many-to-many relationship•Don’t necessarily need a mapping table•User won’t have 1000s of products in cart•Can represent relationship as array in user since one side is small•If one side of many-to-many is bounded and/or small, it is a good candidate for embedding•Arrays that grow without bound are an antipattern!
–16mb document size limit–network overhead
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Part 4: The Express Framework
•Most popular Node.js web framework•Simple, pluggable, and fast•Great tool for building REST APIs
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Your First Express App
Route Parameter
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What is REST?
•Representational State Transfer•HTTP request -> JSON HTTP response•Business logic on top of MongoDB schemas
–Access control, emails, analytics, etc.
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Structuring Your REST API
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GET /category/id/:idFind Category
Error handling
Output JSON
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GET /category/parent/:id
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GET /product/category/:id
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Adding Products to User’s Cart
•Recall cart is an array of products
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Adding Products to User’s Cart
Get cart from HTTP request
Overwrite user’s cart
Let mongoose handlecasting and validating data
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PUT /me/cart Takeaways
•Mongoose lets you be lazy•Access control using subdocs
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Bonus: Stripe Checkout
Create a Stripe charge with the npm ‘stripe’ module
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Bonus: Stripe Checkout
Error handling
Empty user carton success
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Part 4 Takeaways
•Express REST API on top of mongoose–Access control–Business logic–Define what operations user can take on database
•Mongoose casting and validation for APIs
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Part 5: Test-Driven Development•Building an API is tricky•Lots of different error conditions•Express has a lot of magic under the hood
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NodeJS Concurrency and Testing•Node.js runs in an event loop•Single threaded•Can run client and server on same thread!
–Client sends HTTP request–Client registers a callback awaiting the result–Server’s “on HTTP request” event handler is triggered
–Server sends response, continues waiting for events
–Client’s callback gets fired•Test server end-to-end
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Superagent
•NodeJS HTTP client•Isomorphic: runs in both browser and NodeJS•Same author as Express
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Mocha
•Testing Framework for NodeJS•Same author as Express•BDD-style syntax
–describe() -> test suite–it() -> individual test
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Setting Up Category API Tests
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Testing GET /category/id/:id
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Part 5 Takeaways
•NodeJS concurrency makes testing easy•Not just unit tests - full E2E for your REST API•Can manipulate database and make arbitrary HTTP requests
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•Upcoming EdX Video Course•Slides on http://www.slideshare.net/vkarpov15•Looking for beta testers! Sign up for notifications
–http://goo.gl/forms/0ckaJ4YvJN•Interested in learning about AngularJS?
–Professional AngularJS on Amazon•More NodeJS+MongoDB content at:
–www.thecodebarbarian.com–Twitter: @code_barbarian
Thanks for Listening!