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Explanation

Use ResponseEntity to return custom HTTP status codes along with response body. This is the most common and flexible approach in Spring Boot REST APIs.

Code:

@GetMapping("/ok")
public ResponseEntity<String> success() {
  return ResponseEntity.status(
HttpStatus.OK).body("Success"
);
}

Explanation

Return 201 CREATED when a new resource is successfully created, such as saving data into a database.

Code:

@PostMapping("/create")
public ResponseEntity<String> create() {
  return ResponseEntity.status(
HttpStatus.CREATED).body(
"Resource created successfully
");
}

Explanation

Return 400 BAD REQUEST when user input is invalid or missing required parameters.

Code:

@GetMapping("/bad")
public ResponseEntity<String> badRequest() {
  return ResponseEntity.status(
HttpStatus.BAD_REQUEST).body(
"Invalid request data");
}

Explanation

Return 404 NOT FOUND when requested data does not exist in the database.

Code:

@GetMapping("/user/{id}")
public ResponseEntity<String> getUser(
@PathVariable int id) {
  return ResponseEntity.status(
HttpStatus.NOT_FOUND).body("User not found");
}

Explanation

Return 500 INTERNAL SERVER ERROR when unexpected exceptions occur in the application.

Code:

@GetMapping("/error")
public ResponseEntity<String> serverError() {
  return ResponseEntity.status(
HttpStatus.INTERNAL_SERVER_ERROR).body(
"Something went wrong");
}

Explanation

Use @ResponseStatus annotation to directly assign a status code to a controller method.

Code:

@ResponseStatus(HttpStatus.NO_CONTENT)
@DeleteMapping("/delete/{id}")
public void deleteUser(
@PathVariable int id) {
}

Explanation

Use exception handling with @RestControllerAdvice to return different status codes globally across the application.

Code:

@RestControllerAdvice
public class GlobalExceptionHandler {

  @ExceptionHandler(Exception.class)
  public ResponseEntity<String> 
handleException(Exception ex) {
    return ResponseEntity.status(
HttpStatus.INTERNAL_SERVER_ERROR)
                         .body(
ex.getMessage());
  }
}