REST, which stands for Representational State Transfer, is an architectural style for designing networked applications. REST APIs (Application Programming Interfaces) are a type of web API that adhere to the principles and constraints of REST. Here's a breakdown of what REST APIs are and their key characteristics:
- Resources : In REST, everything is considered a resource. Resources can be physical entities (e.g., a user, a product) or abstract concepts (e.g., an order, a comment). Each resource is identified by a unique URI (Uniform Resource Identifier).
- Statelessness : REST APIs are designed to be stateless, meaning that each request from a client to a server must contain all the information needed to understand and process the request. The server should not rely on any previous client requests or maintain session state.
- HTTP Methods : REST APIs use HTTP methods (verbs) to perform CRUD (Create, Read, Update, Delete) operations on resources. The most common HTTP methods used in REST are:
- GET: Retrieve data (read).
- POST: Create a new resource
- PUT: Update an existing resource or create a new one if it doesn't exist
- PATCH: Partially update an existing resource.
- DELETE: Remove a resource.
- Representation : Resources can have multiple representations, such as JSON, XML, HTML, or others. Clients can specify their preferred representation using the HTTP "Accept" header, and servers respond with the requested format.
- Stateless Communication : RESTful interactions between clients and servers are stateless and independent. Each request should contain all necessary information, including authentication credentials if required.
- Uniform Interface : REST APIs have a uniform and consistent interface, which simplifies interactions and makes the API more understandable. This includes the use of standard HTTP methods and status codes.
- Layered System : REST allows for a layered system architecture, where intermediaries (like load balancers or caching servers) can be used to improve scalability, security, and performance without affecting the client or server.
- Client-Server : REST separates the concerns of the client and server. This decoupling allows both the client and server to evolve independently, as long as they adhere to the agreed-upon contract (the API).
- Cacheability : Responses from a REST API can be explicitly marked as cacheable or non-cacheable. Caching can help reduce server load and improve performance.
- Self-Descriptive Messages : REST APIs should include enough information in responses (e.g., using headers and standard media types) to describe how clients can interact with resources.