REST APIs: How They Work and What You Need to Know

What is REST?

In the year 2000, Roy Fielding proposed Representational State Transfer (REST) as a way to structure web services. REST is a design system for creating distributed applications that are linked via hypermedia. The architecture of REST does not rely on any particular transfer protocol and does not have to be associated with HTTP. Despite this, the most usual implementations of REST APIs are using HTTP as their communication protocol, and this guide concentrates on the design of REST APIs meant for the HTTP protocol.

One major benefit of using REST instead of HTTP is that it works with open standards and does not require the API or consumer applications to be tied to any particular implementation. For example, a REST web service may be coded with ASP.NET while client applications are able to use any language or toolset that is able to devise HTTP requests and interpret HTTP responses.

Here are some of the main design principles of RESTful APIs using HTTP:

REST APIs are structured around objects, data, or services that the customer can get to.
A resource has a unique identification, which is a URI that unmistakably distinguishes that resource. For instance, the web address for a certain customer order is: https://adventure-works.com/orders/1
Clients interact with a service by exchanging representations of resources. Many web APIs use JSON as the exchange format. For example, a GET request to the URI listed above might return this response body: {“ordered”:1, “orderValue”:99.90, “productId”:1, “quantity”:1}
REST APIs employ a consistent interface, which helps to separate the customer and service implementations. For APIs based on HTTP that follow the REST architecture, utilizing conventional HTTP commands to carry out activities on objects is an integral part of the consistent interface. The five usual actions are GET, POST, PUT, PATCH, and DELETE.
REST APIs use a stateless request model. Requests made through HTTP should be self-contained and could show up in any sequence, so it is not practical to keep temporary state information between requests. The sole repository of data is within the sources themselves, and every individual request must be concluded in a single step. This limitation allows web services to have a great capacity to expand, as it is not required to build any strong connection between customers and individual servers. Any server can handle any request from any client. That said, other factors can limit scalability. For instance, a lot of web services save information to a database that can be difficult to expand.
Hypermedia links in the representation power REST APIs. An example of a JSON presentation of an order is displayed below. This text has connections to find or revise the patron linked to the order.

In 2008, Leonard Richardson proposed the following maturity model for web APIs:

Level 0: Define one URI, and all operations are POST requests to this URI.
Level 1: Create separate URIs for individual resources.
Level 2: Use HTTP methods to define operations on resources.
Level 3: Use hypermedia (HATEOAS, described below).

Level 3 meets Fielding’s criteria for a truly RESTful API. A lot of web APIs that are printed exhibit characteristics at the level 2 mark.

The Six Rules of REST APIs

In order to get the most out of what REST offers, APIs have to adhere to six prerequisites. Five components are necessary, with an additional one being an option, in order to construct a nimble and dynamic API. These components act as the foundation for such an API.

1. Client-Server Separation

In accordance with the REST approach, communication between the client and server can only flow in one direction: the customer transmits a request and the server responds with an answer sent back to the client. On servers, client-initiated requests are the only type of communication allowed; no response can be initiated by the server.

RESTful APIs make it easy to maintain the separation between clients and servers by facilitating straightforward communication between them. Through this process, client programs can increase their constructs without having to fret about disrupting other web servers, and server elements can be changed without inadvertently impacting clients.

2. Uniform Interface

This rule indicates that both queries and replies have to abide by a unified protocol or a layout for sending and receiving information. Programs and servers are coded in numerous distinct languages that are not competent in communicating and collaborating without an intermediary. A consistent interface provides a shared language that any customer can use to connect with any REST API.

Without a common language for software to utilize, it would be chaos to try and interpret requests and answers between programs. Inconsistent information would make it difficult to track conversations and data would be lost, so software programs would need to periodically adjust their request operations when the API services change. A uniform interface eliminates this possibility.

For most REST application programming interfaces, HTTP (Hyper-Text Transfer Protocol) is the usual language used. HTTP wasn’t created specifically for REST. Rather than using a different communications protocol, REST adopted this particular protocol as its go-to standard for applications.

The Hypertext Transfer Protocol outlines various operations that give purpose and meaning to a request. The common HTTP methods used by most RESTful web APIs are:

GET retrieves a representation of the resource at the specified URI. The body of the response message contains the details of the requested resource.
POST creates a new resource at the specified URI. The body of the request message provides the details of the new resource. Note that POST can also be used to trigger operations that don’t actually create resources.
PUT either creates or replaces the resource at the specified URI. The body of the request message specifies the resource to be created or updated.
PATCH performs a partial update of a resource. The request body specifies the set of changes to apply to the resource.
DELETE removes the resource at the specified URI.

The impact of making an individual request should be different depending on if the resource is a group or a singular item. This table outlines the most popular conventions widely used by implementations of RESTful services in the e-commerce sector. It is possible that not all of these demands will be satisfied; it depends on the precise situation.

It can be difficult to differentiate between POST, PUT, and PATCH.

A POST request creates a resource. The server provides a URI to the client which has been allocated to the new source. In the REST system, it is common to submit POST requests to database collections. The new resource is added to the collection. It is possible to send data to an existing resource for processing using a POST request, without having to create anything new.
A PUT request creates a new object or modifies an existing object. The client specifies the URI for the resource. The request includes all the necessary details of the resource. If a resource already exists with this Universal Resource Identifier, it will be replaced. If the server is able to do it, a fresh resource will be created. Requests that use the PUT method are usually associated with single resources, like an individual customer, instead of groups. A server might permit changes to be made via updates, but not allow things to be created through the PUT method. The choice of whether to back the manufacturing of a resource through PUT relies on whether the customer can assign a pertinent URI to the asset before it is created. If no other method applies, utilize POST to generate new sources and PUT or PATCH to modify existing ones.
A PATCH request modifies a portion of an already existing resource. The client specifies the URI for the resource. The request body indicates a group of modifications to be made to the resource. This method of operation is more effective compared to using PUT since the customer only sends the modifications rather than the overall representation of the resource. PATCH can create a new resource if the server allows it by specifying a group of changes to a resource that doesn’t exist.

PUT requests must be idempotent. If the same PUT request is sent out by a customer repeatedly, the outcome should stay consistent (the exact same resource will be modified with the exact same values). Sending POST and PATCH requests cannot be assured to not have any effect if repeated multiple times.

3. Stateless

All calls with a REST API must be stateless. This implies that each encounter is separate, and each demand and answer gives all the information needed to finish the connection. The server takes each request from the client and considers them as new, without retaining data from previous queries.

Transfers without a state considerably lessen the quantity of server memory that is needed and increase the chances that the response will be successful because the server does not have to conduct any further action to get the previous data. This makes it so that these conversations can be expansive: As the software increases and demands more, coders don’t need to stress over a large quantity of memory being consumed or an overload of requests on the server.

4. Layered System

Thus far, I have made API requests look like a straightforward interaction between a client and server, which is a slight oversimplification. Generally speaking, there are usually multiple servers between these two entities. These servers, known as layers, are employed to boost security, divide and control traffic, as well as aid with other essential tasks.

This rule necessitates that communication between the sender and the intended server must continually be framed and handled consistently, irrespective of any layers in between them. Additional layers should not affect client-server interactions.

If this rule is followed by coders, server systems can be reconfigured, upgraded, or otherwise adjusted with no outcome on the essential request response.

5. Cacheable

When an individual visits a website, the media present on the site is stored on their device as part of the caching process. When someone revisits the website, the saved information stored on the computer is displayed rapidly instead of being pulled from the server once more. Many large websites opt for caching as a way to protect their server resources and bandwidth while increasing their page loading speeds.

REST APIs are created with data caching in mind. When a server sends an answer to a customer, the answer should clarify if the offered asset can be held in the cache, and for how long.

6. Code on Demand (Optional)

The final REST principle is optional. It is possible for an API to deliver computer code to its clients as part of its output if desired. This gives the client the ability to execute the code on their own server.

If an API follows this set of regulations, it can be labeled a RESTful API. Nonetheless, these protocols still offer developers a variety of options to modify the operation of their Application Programming Interface. REST APIs are more adaptive than the Simple Object Access Protocol (SOAP), setting them apart.

REST API vs. SOAP API

REST is typically juxtaposed with SOAP, a means to create applications that run on HTTP. The primary dissimilarity between REST and SOAP is that REST is a series of rules, and SOAP is a method of communication. REST facilitates the construction of APIs using any kind of protocol, such as HTTP, URLs, and JSON. SOAP only uses XML for sending data.

REST is seen as a simpler, more effective replacement for SOAP as it necessitates producing less code to attain objectives and abides by a less set-in-stone framework and reasoning than SOAP. REST provides guidelines for constructing APIs, leaving a lot of decisions to be made by the designer of the API.

Why use REST APIs?

Roy Fielding’s REST framework was created in the year 2000 and continues to shape our view, alteration, and movement of content while on the internet. A lot of the top-ranking web and cloud companies employ REST APIs in their applications, such as Facebook, YouTube, Twitter, and Google.

But why REST? Basically, it’s an excellent system for web apps. Here are the main benefits of this type of API:

REST APIs are flexible. They can handle many types of requests and send data in many different formats.
REST APIs are scalable. They are designed for communication between any two pieces of software, regardless of size or capability. As a web application grows and adds more resources, its REST API will be able to quickly handle the increasing amount and variety of requests.
REST APIs incorporate existing web technologies, making them relatively easy to build and use. To request a resource via a REST API, you just need to provide its URL.

Don’t Sleep on REST

There is a wide-held opinion that the REST API will become the predominant communication approach on the web in the near future, and it is not hard to view why this is the case. They make it possible for any two internet-connected programs to exchange data and interact, regardless of their size or features. Via REST, a tiny start-up can be connected to a mammoth government agency and the other way around.

Software programs can build revolutionary and creative systems by collaborating, which would be a desirable addition to any digital platform as it expands. If you have an app that needs to be connected to other software, don’t forget about the potential of REST.