Initial setup

• Install postman https://www.getpostman.com/

• Download workshop materials• Install nodejs https://nodejs.org/en/• Github repo http://bit.ly/2cMeCm1• Signup for PP – https://www.paypal.com/signup/account

• Postman collection http://bit.ly/2dkWFwj

NTU Workshop: Using REST APIs

Aeshan WijetungeDeveloper@PayPal

Objectives

• Appreciate the benefits of leveraging public APIs

• Understand basics of calling a REST APIs• Can make payments using the PayPal API• Understand the benefits of Asynchronous

programming• Create a mashup of PayPal APIs leverging the

Async library

What is a REST API?

• REpresentational State Transfer• Context of Web Services• URLs (e.g:

https://api.github.com/users/aeshanw)• Interface to Resources over the Internet

Credit: http://www.robert-drummond.com/

Simple Example

Credit: Salesforce https://developer.salesforce.com/page/REST_API

Being RESTful

• APIs are Resource-centric• REST is built-atop the HTTP protocol• HTTP is the infrastructure of the Internet• REST APIs (a.k.a web services) support– GET– POST– PUT– DELETE

Anatomy of HTTP

Credits: http://cis.msjc.edu/ Mt San Jacinto College

Calling a simple API

• Fetch github user details • https://api.github.com/users/aeshanw• Response can be viewed on a web browser• This is a GET operation• What about POST/PUT/DELETE?– We need a more advanced tool to work with REST

APIs

Introducing POSTMAN

• Tool for working with REST APIs • As a developer you can– Customize the HTTP Headers of request– Authenticate your requests to protected APIs• Supports Oauth for this purpose

Using POSTMAN

• Import the POSTMAN collection:– https://www.getpostman.com/collections/

b0038ed98853ba7e1b10• Call the github URI with POSTMAN• Note the status code and response headers

PayPal APIs

• A huge collection of APIs handling– Payments– Invoicing– Billing Agreements

• Our focus will be on– Storing a credit card on the Vault API– Making a payment with the Vaulted card

PayPal Secured by OAuth

• Similar to log-in with username & password• You need a PayPal account (personal)• Authenticate via v1/oauth2/token API• Get your clientID & secret• POSTMAN Authorization tab– Select `Basic Auth` Type– Username clientID– Password secret

Authenticating your requests

v1/oauth2/token v1/vault/credit-cards

/v1/payments/payment

clientID + secret AccessToken

AccessToken

Add credit card

• Using /v1/vault/credit-cards• Request Body is in a JSON-format• Request Headers include the AccessToken

credit cards for testing

• PayPal sandbox is for testing only• Allows use of dummy cards for testing• Use this site for generating credit card

numbers for testing

• http://www.freeformatter.com/credit-card-number-generator-validator.html

Pay with a Vaulted card

v1/oauth2/token

v1/vault/credit-cards

v1/payments/payment

AccessToken

CardToken

PaymentID

Try this in POSTMAN

• Use the POSTMAN collection provided earlier• Use POSTMAN global variables to store the

AccessToken to be used in subsequent requests

• Exercise– Get Token (Authenticate)– Add a card to vault– Make a payment with the vaulted card

Getting started with Node.js

• Let’s make the calls from our application• Using node.js as an example, but concepts

valid in any language.• Exercise : Run the node.js app locally– $ npm install– $ npm start– Goto http://localhost:8000/

API calls from node.js

• Use the request module as REST Clienthttps://www.npmjs.com/package/request

• Look for Lab 1.0a in demoapp/controllers/index.js

Optimization• What if you need to add several cards at

once?

addCard1 payWithCard1 addCard2 payWithCard2

• Is there a faster way?• Yes, Parallelization

Going in Synch• Java Synchronous example

Now in Async

• Javascript example

Asynchronous Complexity

• Many languages support Asynchronous libraries. E.g: Python, Java, Javascript, Scala, Erlang…

• But, Developing code that is Asynchronous can be difficult.

• Thankfully most modern languages provide libraries to manage the complexity

• Async is popular among Javascript developers

Using Async

• Docs here https://www.npmjs.com/package/async

• Async can execute your code– In series– In parallel

Async series

• Call the APIs in sequence one after the other• Run nodeserv dummy service to better

understand the difference– $ cd nodeserv– $ npm install– $ node index.js

• Look for Lab 1.1a in demoapp/controllers/index.js

Async series workshop

• Nodeserv has a 5 sec time-delay to simulate I/O latency

• How long would this lab code take to call the task API twice?

Async parallel

• Call the APIs in parallel• Look for Lab 1.1b in

demoapp/controllers/index.js • Did you notice any difference in the time taken

to call the API twice?

PayPal Integration

• Let’s integrate the vaulted-card solution into our node.js application

• First, we need to get the access_token• Look for Lab 2.0 in

demoapp/controllers/index.js • Test the api-call by hitting

localhost:8000/gettoken• Ensure you get the access_token

Vault the card

• Pass the access_token to a funtion which adds the card to vault

• Look for Lab 2.1 in demoapp/controllers/index.js

• Ensure you get the card_token from the vault API response

• Test the api-call by hitting localhost:8000/addcard

Make Payment

• Use case: We need to split a big payment into 2 credit cards due to some credit-limits on each card

• Parallelize the vaulting of 2 cards• Parallelize the 2 payments using the card

tokens• Look for Lab 2.2 in

demoapp/controllers/index.js

Fix the code

• Fix the payment api call in payWithToken • Parallelize the functions addCardToVault &

payWithToken in order to complete the tasks as efficiently as possible.

• Test the calls by hitting localhost:8000/paywithvault– Check the logs to verify the result

Bonus lab (optional)

• Notice that the Card Tokens are logged to console

• Can we lookup the Vaulted Card details?• Lookup the PayPal Vault API to do this

Recap

• Appreciate the use of APIs in applications• Call a RESTful API using POSTMAN• Call a RESTful API from an application• Debug API Integrations using logs• Parallelize API calls with Async libraries

Beyond Javascript

• Many languages support Async– Python– Java

So what’s stopping you from using it in your next application?

Thanks!

• https://github.com/nodeworkshop/ntu_2016_async_workshop

• PP Sample Cards • https://www.paypalobjects.com/en_US/

vhelp/paypalmanager_help/credit_card_numbers.htm