REST
INFO 253A: Frontend Web Architecture
Kay Ashaolu
REST
Representational State Transfer
Good news, everyone!
- You already know REST
- Representations (HTML! but also XML, JSON)
- State
- Transfer
History
- Roy Fielding co-wrote HTTP specs
- Defined REST in his 2000 PhD dissertations
- Defined core set of constraints and why they were important
Constraints
- Client-server: Two separate systems talk to each other through a well defined interface
- Stateless: No context is stored between requests
- Cacheable: Clients or intermediaries can cache results, and requests and results can specify caching information
Constraints
- Layered: Requests can go through intermediaries (proxies)
- Uniform Interface: The protocol between client and server follows the same rules regardless of the specific application
Client-Server
Pros
- Browsers don't care what web server is providing representations, or which database is holding data
- Servers don't care which clients are connecting
Cons
- Overhead of transferring data
- Fewer, simpler failure modes
Stateless
Pros
- Simplifies server design and storage
- Simplifies request grammar
- Improves scalability, error recovery
Cons
- Overhead of transferring client state
- Not convenient for interactivity at protocol level
Cacheable
Pros
- Browsers can store CSS and JavaScript
- Businesses can cache responses, even from external sites
- Servers can specify how long things should be cached for
Cons
- Cache invalidation is hard
- Can't rely on updated resources updating "everywhere"
Uniform Interface
Pros
- Client and server know how to interact regardless of application hosted
- Pinterest uses same interface as Yelp
- Wider variety of clients that can handle multiple applications
Cons
- For really unique applications, must jam into old paradigms
- Difficult to optimize for performance of single application
REST is not HTTP
- Remember HTTP is a transport protocol: a tube!
- REST is a set of constraints on how to use that tube
- We could use other tubes, like FTP, SMTP
Web is RESTful
- Web is build on these ideas
- Better leverage attained by embracing REST
- Flexibility, scalability, visibility, simplicity
How to Spot RESTfulness
- Should think through constraints, but here are some heuristics
Uses HTTP
- REST is the underlying architectural principle of the web
- The web primarily uses the HTTP protocol
- The way browsers interface with web servers is inherently RESTFul if you think about it
Uses HTTP Commands
- GET, POST, PUT...
- vs using POST for everything
Uses HTTP response codes
- 404 Not Found, 200 OK
- vs. always responding with 200 OK but has an error message
URLs point to resources
- /blog, /api/messages/34
- vs. URLs pointing to commands: /api/createBlog, /api/getMessage/34
Representation links
- A representation links to new possible actions
- Client only needs to have representation
- Hypermedia as the engine of application state (HATEOAS)
Example
{
"business": "http://yelp.com/biz/27",
"user": "http://yelp.com/user/5",
"review_text": "..."
}
Counter Example
data = {
"business_id": 27,
"user_id": 5
"review_text": "..."
}
fetch(`http://yelp.com/biz/${data["business_id"]}`).then((response) => {
...
});
Uses headers for meta data
- Content-Type XML or JSON
- vs. response has extra meta data in XML
Questions?
REST - Frontend Webarch
By kayashaolu