REpresentational State Transfer
REST, or REpresentational State Transfer, is an architectural style for providing standards between computer systems on the web, making it easier for systems to communicate with each other. REST-compliant systems, often called RESTful systems, are characterized by how they are stateless and separate the concerns of client and server. We will go into what these terms mean and why they are beneficial characteristics for services on the Web. Pay close attention: If you’re looking for a career in tech, you may be asked to define rest during an interview.
Separation of Client and Server
In the REST architectural style, the implementation of the client and the implementation of the server can be done independently without each knowing about the other. This means that the code on the client side can be changed at any time without affecting the operation of the server, and the code on the server side can be changed without affecting the operation of the client.
As long as each side knows what format of messages to send to the other, they can be kept modular and separate. Separating the user interface concerns from the data storage concerns, we improve the flexibility of the interface across platforms and improve scalability by simplifying the server components. Additionally, the separation allows each component the ability to evolve independently.
By using a REST interface, different clients hit the same REST endpoints, perform the same actions, and receive the same responses.
Statelessness
Systems that follow the REST paradigm are stateless, meaning that the server does not need to know anything about what state the client is in and vice versa. In this way, both the server and the client can understand any message received, even without seeing previous messages. This constraint of statelessness is enforced through the use of resources, rather than commands. Resources are the nouns of the Web - they describe any object, document, or thing that you may need to store or send to other services.
Because REST systems interact through standard operations on resources, they do not rely on the implementation of interfaces.
These constraints help RESTful applications achieve reliability, quick performance, and scalability, as components that can be managed, updated, and reused without affecting the system as a whole, even during operation of the system.
Now, we’ll explore how the communication between the client and server actually happens when we are implementing a RESTful interface.
Communication between Client and Server
In the REST architecture, clients send requests to retrieve or modify resources, and servers send responses to these requests. Let’s take a look at the standard ways to make requests and send responses.
Making Requests
REST requires that a client make a request to the server in order to retrieve or modify data on the server. A request generally consists of:
- an HTTP verb, which defines what kind of operation to perform
- a header, which allows the client to pass along information about the request
- a path to a resource
- an optional message body containing data
HTTP Verbs
There are 4 basic HTTP verbs we use in requests to interact with resources in a REST system:
GET — retrieve a specific resource (by id) or a collection of resources
POST — create a new resource
PUT — update a specific resource (by id)
DELETE — remove a specific resource by id
Paths
Requests must contain a path to a resource that the operation should be performed on. In RESTful APIs, paths should be designed to help the client know what is going on.
Conventionally, the first part of the path should be the plural form of the resource. This keeps nested paths simple to read and easy to understand.
A path like fashionboutique.com/customers/223/orders/12 is clear in what it points to, even if you’ve never seen this specific path before, because it is hierarchical and descriptive. We can see that we are accessing the order with id 12 for the customer with id 223.
Paths should contain the information necessary to locate a resource with the degree of specificity needed. When referring to a list or collection of resources, it is not always necessary to add an id. For example, a POST request to the fashionboutique.com/customers path would not need an extra identifier, as the server will generate an id for the new object.
If we are trying to access a single resource, we would need to append an id to the path. For example: GET fashionboutique.com/customers/:id — retrieves the item in the customers resource with the id specified. DELETE fashionboutique.com/customers/:id — deletes the item in the customers resource with the id specified.
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