What is a REST API?

  • An API is a set of definitions and protocols for building and integrating application software. It’s sometimes referred to as a contract between an information provider and an information user—establishing the content required from the consumer (the call) and the content required by the producer (the response). For example, the API design for a weather service could specify that the user supply a zip code and that the producer reply with a 2-part answer, the first being the high temperature, and the second being the low.
  • In other words, if you want to interact with a computer or system to retrieve information or perform a function, an API helps you communicate what you want to that system so it can understand and fulfill the request.
  • You can think of an API as a mediator between the users or clients and the resources or web services they want to get. It’s also a way for an organization to share resources and information while maintaining security, control, and authentication—determining who gets access to what.
  • Another advantage of an API is that you don’t have to know the specifics of caching—how your resource is retrieved or where it comes from.

What is meant by REST API?

REST is a set of architectural constraints, not a protocol or a standard. API developers can implement REST in a variety of ways.

When a client request is made via a RESTful API, it transfers a representation of the state of the resource to the requester or endpoint. This information, or representation, is delivered in one of several formats via HTTP: JSON (Javascript Object Notation), HTML, XLT, Python, PHP, or plain text. JSON is the most generally popular file format to use because, despite its name, it’s language-agnostic, as well as readable by both humans and machines.

Something else to keep in mind: Headers and parameters are also important in the HTTP methods of a RESTful API HTTP request, as they contain important identifier information as to the request’s metadata, authorization, uniform resource identifier (URI), caching, cookies, and more. There are request headers and response headers, each with their own HTTP connection information and status codes.

In order for an API to be considered RESTful, it has to conform to these criteria:

  • A client-server architecture made up of clients, servers, and resources, with requests managed through HTTP.
  • client-server communication, meaning no client information is stored between get requests and each request is separate and unconnected.
  • Cacheable data that streamlines client-server interactions.
  • A uniform interface between components so that information is transferred in a standard form. This requires that:
    • resources requested are identifiable and separate from the representations sent to the client.
    • resources can be manipulated by the client via the representation they receive because the representation contains enough information to do so.
    • self-descriptive messages returned to the client have enough information to describe how the client should process it.
    • hypertext/hypermedia is available, meaning that after accessing a resource the client should be able to use hyperlinks to find all other currently available actions they can take.
  • A layered system that organizes each type of server (those responsible for security, load-balancing, etc.) involved the retrieval of requested information into hierarchies, invisible to the client.
  • Code-on-demand (optional): the ability to send executable code from the server to the client when requested, extending client functionality.

Though the REST API has these criteria to conform to, it is still considered easier to use than a prescribed protocol like SOAP (Simple Object Access Protocol), which has specific requirements like XML messaging, and built-in security and transaction compliance that make it slower and heavier.

What is REST API example?

An API, or application programming interface, is a set of rules that define how applications or devices can connect to and communicate with each other. A REST API is an API that conforms to the design principles of the REST, or representational state transfer architectural style. For this reason, REST APIs are sometimes referred to RESTful APIs.

First defined in 2000 by computer scientist Dr. Roy Fielding in his doctoral dissertation, REST provides a relatively high level of flexibility and freedom for developers. This flexibility is just one reason why REST APIs have emerged as a common method for connecting components and applications in a microservices architecture.

How does REST API work?

REST APIs communicate via HTTP requests to perform standard database functions like creating, reading, updating, and deleting records (also known as CRUD) within a resource. For example, a REST API would use a GET request to retrieve a record, a POST request to create one, a PUT request to update a record, and a DELETE request to delete one. All HTTP methods can be used in API calls. A well-designed REST API is similar to a website running in a web browser with built-in HTTP functionality.

The state of a resource at any particular instant, or timestamp, is known as the resource representation. This information can be delivered to a client in virtually any format including JavaScript Object Notation (JSON), HTML, XLT, Python, PHP, or plain text. JSON is popular because it’s readable by both humans and machines—and it is programming language-agnostic.

Request headers and parameters are also important in REST API calls because they include important identifier information such as metadata, authorizations, uniform resource identifiers (URIs), caching, cookies and more. Request headers and response headers, along with conventional HTTP status codes, are used within well-designed REST APIs.

How do I access REST API?

REST implements multiple ‘methods’ for different types of request, the following are most popular:
– GET: Get resource from the server.
– POST: Create resource to the server.
– PATCH or PUT: Update existing resource on the server.
– DELETE: Delete existing resource from the server.
Headers: The additional details provided for communication between client and server (remember, REST is stateless). Some of the common headers are:
Request:
– host: the IP of client (or from where request originated)
– accept-language: language understandable by the client
– user-agent: data about client, operating system and vendor
Response:
– status: the status of request or HTTP code.
– content-type: type of resource sent by server.
– set-cookie: sets cookies by server
Data: (also called body or message) contains info you want to send to the server.

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