1. Node.js Express Web Services
Microsoft Virtual Academy
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Mastering Node.js, Part 5
Node.js Express Web Services
Eric W. Greene
Produced by

2. Course Overview Getting Started with Express REST Services
Configuring Routers
Extracting Data from the URL
Working with a Request Body
JSON Web Token Authentication with Passport

3. Getting Started with Express REST Services
The course assumes some basic knowledge of Node.js and the JavaScript programming language
To run the examples on your machine, you will need Node.js installed
Node.js can be downloaded from here:
Install version 6 or later
If you do not understand the basics of these technologies, then watch the WintellectNOW courses, Introduction to Node.js, Node.js Modules & Node.js Packages

4. Getting Started with Express REST Services
Express is a Web Framework used to configure Node's HTTP module
Fast
Un-opinionated
Minimalist
Express is distributed via an NPM package
Express should be installed locally to each project, not globally
To install: npm install express

5. Getting Started with Express REST Services

6. Getting Started with Express REST Services
Provides support for routing and serving static files
Almost all other functionality is provided through third-party middleware modules
Processing request body – Body Parser
Handling Authentication – Passport
JSON Web Tokens – Passport JWT

7. Getting Started with Express REST Services
REST – Representational state transfer
The concept of REST originated from Roy Fielding's doctoral dissertation from his studies at UC Irvine (source:
REST is a convention not a standard such as SOAP
Organizations implement REST web services differently, but there are common goals and patterns

8. What are the Key Concepts of REST Services?
Client-Server – Client and server are ignorant of each other's implementation and execution state
Stateless – No state is maintained between REST requests, each request is completely independent from another request
Cacheable – Responses to requests can be marked or not marked as cacheable, where possible caching should be used to improve performance

9. What are the Key Concepts of REST Services?
Interface - When implemented with HTTP, interaction is between a web client and web server, HTTP verbs indicate the action to perform, and URIs indicate which resource(s) that action is performed on

10. Conventions of REST Services
Two URIs: Collection URI and the Element URI
Collection URI
resource name>
Element URI
resource name>/<resource id>
These two URIs combined with HTTP verbs provide the interface to all of the REST service operations

11. Conventions of REST Services
Most Common Operations
GET <collection uri> - returns all resources
GET <element uri> - returns one resource
POST <collection uri> - inserts a new resource
PUT <element uri> - replaces or inserts a new resource
DELETE <element uri> - delete an existing resource

12. Conventions of REST Services
Update or Replace?
Many times updating a resource is preferred over replacing; therefore, the PATCH verb with the element URI is commonly used for updating
When updating, only the fields to be replaced are included request body
For POST and PUT operations, the request body contains the data to be inserted or replaced
Either XML or JSON can be used, but JSON is by far the most common

13. Using Express to implement REST Services
Using Express and its associated middleware, REST services can be configured and coded
Supports:
Common REST service HTTP verbs
Extracting of element URI ids from the URL
Handling of XML and JSON request body data (JSON is preferred and covered in this course)
Authentication with JSON Web Tokens

14. REST Clients
REST clients are tools designed to allow for easy interaction with REST services
Unlike a standard web browser, the user can easily choose the HTTP verb, specify headers, and provide request bodies in almost any reasonable format

15. REST Clients
REST clients will execute the request and typically deliver results in a raw or formatted output
Popular REST Clients include…
Postman -
Advanced REST Client -

16. Creating a Hello World Express REST Service

17. Routing REST Service Requests
Express provides a powerful Router object which can be used to configure complex routes which detect HTTP verbs and URL path patterns
Routers are really middleware, which are mountable on any path
Route handlers have access to the request and response objects
Routers provide a route method to define a URL path for the route and allows for easy configuring of handlers for common HTTP verbs

18. Configuring a Router

19. Extracting Data from the URL
Two kinds of data are available in the URL
URL Parameters – exposed as params property of the request object
Query String Parameters – exposed as the query property on the request object (not used as part of REST service conventions)
URL Parts
:8080 /person/2 ?detailed=true #home |
Protocol
Domain Name / IP Address
Port
Path
Query String
Client-Side

20. Working with URL Parameters

21. Working with a Request Body
Express does not directly support processing of the request body
Instead, middleware can be used to process the request body
Body Parser – used to process URL encoded and JSON content
Multer (and many others) – used to process file uploads
Without middleware, the request body is accessible through a Node.js stream, and the stream data can be read and processed manually

22. Working with a Request Body
Body Parser determines whether to process the request body as URL encoded of JSON data based upon the request Content-Type
Body Parser makes the data available through the body property on the request object
Body Parser should be loaded before any routes which need access to the request body data
Most REST services today use JSON as the preferred data format

23. Extracting JSON Data from the Request Body

24. Authentication with Passport
Authentication for Express is commonly provided by Passport
Passport provides many different strategies for authenticating users
User accounts stored in local databases
Facebook, Twitter, Google
OAuth and OAuth2 Providers
WS Federation and SAML2
JSON Web Tokens (we will use this for REST service authentication)

25. Authentication with Passport

26. Authentication with Passport
Passport relies express-session middleware to use session-based cookies to track logged in users
Sessions are not required if credentials like an API-key are provided on every request
Passport is well suited for user applications as well as REST services
We will explore a REST service authentication without sessions using JSON Web Tokens

27. Authentication with Passport
For REST services, the JSON Web Token (JWT) strategy can be used
To install this strategy: npm install passport-jwt
JSON Web Tokens are on open standard for representing claims between two parties (RFC
The JSON part of JWT means that JSON is the data format to store the claim
Web Tokens part of JWT are the claim itself structure with a header, payload and signature

28. Authentication with Passport
JSON Web Tokens JSON Structure
Header – typically contains the type of token and hash algorithm being used
Payload – contains the claims themselves
Signature – is a hash of the header and payload values, and is use to verify the sender
More Information:
Debugger Tool: (Click Debugger at the Top)

29. Passport Authentication with JSON Web Tokens

30. Conclusion Express is a Node.js web framework
It makes configuring the Http Server a lot easier
Its routing and middleware capabilities greatly simplify the creation of REST services
Through middleware, multiple authentication strategies are supported such as JSON Web Tokens
Popular, easy to use, and very flexible