What methods and principles can be used to implement REST API when designing web services?

REST API is built on the principles of REST (Representational State Transfer), which include:

• Using standard HTTP methods: GET (retrieve data), POST (create), PUT/PATCH (update), DELETE (delete).
• Resource-oriented architecture: each object or entity has a unique URI.
• Statelessness: each request contains all the necessary information.
• Using standard HTTP response codes to indicate the result of an operation.

When designing a REST API:

• Define resources and their hierarchy in the URL, for example, /users/{id}/orders.
• Use the correct HTTP methods for operations.
• Data format is usually JSON.
• Add pagination, filtering, and sorting if necessary.

Example of a simple REST API in Java using Spring Boot:

@RestController
@RequestMapping("/users")
public class UserController {

    @GetMapping("/{id}")
    public User getUser(@PathVariable Long id) {
        // logic to get user
    }

    @PostMapping
    public User createUser(@RequestBody User user) {
        // logic to create user
    }

    @PutMapping("/{id}")
    public User updateUser(@PathVariable Long id, @RequestBody User user) {
        // logic to update user
    }

    @DeleteMapping("/{id}")
    public void deleteUser(@PathVariable Long id) {
        // logic to delete user
    }
}