Week 08: REST API, OpenAPI
PB138 - Se minar 08
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Agenda
> GET /info/agenda
> Host: tutor.pb138
< HTTP/1.1 200
< Content-Type: text/markdown;charset=utf-8
< Server: Tutor
<
< - Express.js
< - REST API
< - Naming activity
< - CRUD
< - OpenAPI
< - REST Client
< - Jest
< - Testing your API
< - Demo
< - REST, Swagger, Jest
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Express.js - Web Application Framework
Framework that allows quickly building web applications and REST APIs
Provides a very minimal, precise set of tools necessary for creating web applications
Used by many other JS/TS frameworks as their backbone
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Express - Install
npm i express
npm i -D @types/express
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Adding express to the code
import express, { Express, Request, Response } from 'express';
const app: Express = express();
const port = 8080;
app.listen(port, () => {
console.log(`Server is running at https://localhost:${port}`);
});
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Express - routes and handlers
The data is firstly processed by a pipeline of functions called middleware
These functions can, for example, check privileges or handle things that need to happen to every request
before it is processed individually
The request then gets processed via a router
Router then routes the requests it defines the flow of individual requests
Each route has an assigned handler - a function that processes the request individually
// continuation of the code from the previous slide
app.get('/', (req: Request, res: Response) => {
res.send('Express + TypeScript Server');
});
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Let's learn by doing...
... by saving animals from shelter!
Background story:
Animal Crossing is mobile application that provides to potential pet
owners simple and intuitive interface to adopt animal

from shelter. After making an adoption request the new owner will receive
guidelines for petting. Application also provides

access for caretakers to add a pet for adoption or mark it as adopted.
Every shelter must include REST API interface for application which
connect to Central API, to gather the data.
Note: All images are provided by OBČIANSKE ZDRUŽENIE TULÁČIK in
Brezno utuloktulacik.sk, cute dog is named Tootsie

Note: Application is inspired by Bc. Xuan Linh Phamová
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Let's get creative!
After a basic understanding of the project description, now find the exact functional requirements of our
service that needs to be implemented.
Think about animals...
What about requests for adoption from users?
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Let's get creative!
Add animal
Mark animal as adopted
Browse animals
Filter animals by type
Request adoption
You probably thought of more than these, it's good, but we
are only demoing.
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From functional requirements to resources
What are the resources and endpoints here? What endpoints need to be implemented?
Add animal
Browse animals
Filter animals by type
Request adoption
Mark animal as adopted
Think of previous functions and try to find resources.
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We have two models, one for Animals and another one for adoption requests.
model Animal { model Request {
name String from String
description String isAccepted Boolean
age Float
sex Boolean animal Animal
type String
picture String createdAt DateTime @default(now())
acceptedRequest Request? deletedAt DateTime?
requests Request[] }
addedAt DateTime
adoptedAt DateTime?
}
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From functional requirements to REST API
Add animal
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From functional requirements to REST API
POST /animals
JSON Body
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From functional requirements to REST API
Browse animals
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From functional requirements to REST API
GET /animals
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From functional requirements to REST API
Filter animals by type and limit or other
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From functional requirements to REST API
GET /animals?type=dog|cat&limit=2
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From functional requirements to REST API
Request adoption
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From functional requirements to REST API
POST /requests
JSON Body
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From functional requirements to REST API
Mark animal as adopted
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From functional requirements to REST API
PATCH /requests
JSON Body (isAccepted)
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That's it let's implement it!
API is written in Express.js
Documentation written in OpenAPI
Testing in Jest
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