Developing a Basic REST API from Scratch Using TDD

Valeri KarpovNodeJS Engineer, MongoDBwww.thecodebarbarian.com

github.com/vkarpov15@code_barbarian

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What is this talk about?

•Earlier you heard about:– Building a basic app– Schema design principles

•MongoDB is great for storing web/mobile app data•So let’s build a REST API using NodeJS!•+ learn a bit about test-driven dev with NodeJS

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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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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

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Part 2: Using the Mongoose ODM

•“Object document mapper” (like ORM, but for MongoDB)•Written for NodeJS•Provides schema validation

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Brief Overview of NodeJS

•require()

● Async I/O

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Your First Mongoose Schema

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Using Your Schema

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Using Your Schema

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Part 3: Schema Design

•3 schemas:– Product– Category– User

•Going to use mongoose to define schemas

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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•“Store what you query for”•“If you need [to use the aggregation framework in an API endpoint], you're screwed anyway, and should fix your program.” - Linus Torvalds

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User Schema

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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•Arrays that grow without bound are an antipattern!

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Part 4: The Express Framework

•Most popular NodeJS web framework•Simple, pluggable, and fast•Great tool for building REST APIs

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Your First Express App

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Your First Express App

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Your First Express App

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What is REST?

•Representational State Transfer•HTTP request -> JSON HTTP response•Business logic on top of MongoDB schemas

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Structuring Your REST API

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GET /category/id/:id

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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

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PUT /me/cart Takeaways

•Mongoose lets you be lazy•Access control using subdocs

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Bonus: Stripe Checkout

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Bonus: Stripe Checkout

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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

•NodeJS runs in an event loop•Single threaded•Can run client and server on same thread!•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

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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•Looking for beta testers! Fill out survey for info

– database.mongodb.com/community-survey•More NodeJS+MongoDB content at:

– www.thecodebarbarian.com– Twitter: @code_barbarian

Thanks for Listening!