REST API Development Interview Questions

Create a class with @RestController, map methods with @GetMapping, @PostMapping, and related annotations, accept input with @RequestBody or parameters, and return a domain object or ResponseEntity.

@RequestMapping is the general mapping annotation and can specify path and HTTP method. @GetMapping, @PostMapping, @PutMapping, @PatchMapping, and @DeleteMapping are shorter, clearer specialized forms.

@PathVariable reads a value from the URL path, such as /users/42. @RequestParam reads a query parameter, such as /users?page=2.

@RequestBody tells Spring to read the HTTP request body and convert it, commonly from JSON, into a Java object using an HttpMessageConverter.

@ResponseBody tells Spring to write a method’s return value to the HTTP response body. @RestController applies this behaviour to all handler methods by default.

ResponseEntity represents the complete HTTP response, including body, status code, and headers. It is useful when an endpoint must control the response precisely.

Return ResponseEntity.status(...), use ResponseEntity.ok(), created(), noContent(), or annotate an exception and handler with @ResponseStatus. Choose codes that describe the result clearly.

Add the validation starter, place constraints such as @NotBlank or @Size on a request DTO, and use @Valid in the controller. @Validated also supports validation groups and method-level validation.

Add the validation starter, place constraints such as @NotBlank or @Size on a request DTO, and use @Valid in the controller. @Validated also supports validation groups and method-level validation.

Create an annotation with @Constraint, implement ConstraintValidator, and return false when the value is invalid. Add a clear message and apply the annotation to the DTO field or class.

@RestControllerAdvice defines handlers shared by controllers. @ExceptionHandler maps an exception to a consistent response, so controllers do not repeat try-catch code.

@RestControllerAdvice defines handlers shared by controllers. @ExceptionHandler maps an exception to a consistent response, so controllers do not repeat try-catch code.

Use a stable response containing fields such as timestamp, status, error code, message, path, and validation details. Avoid exposing stack traces or internal database information to clients.

Common choices are a version in the path such as /api/v1/users, a request header, or a media type. Pick one strategy and document it consistently for clients.

Accept page, size, and sort parameters, validate their limits, and return a Page or a custom response containing items and paging metadata. Spring Data Pageable can bind these values automatically.

Configure CORS with @CrossOrigin for a small case or a WebMvcConfigurer or Spring Security configuration for application-wide rules. Allow only trusted origins and required methods.

Content negotiation lets a client and server agree on a response representation such as JSON or XML. Spring uses request headers, URL patterns, and configured converters to choose the representation.

Spring Boot auto-configures Jackson when it is on the classpath. ObjectMapper converts Java objects to JSON and JSON request bodies back to Java objects; annotations or a configured ObjectMapper customize the process.

Spring Boot auto-configures Jackson when it is on the classpath. ObjectMapper converts Java objects to JSON and JSON request bodies back to Java objects; annotations or a configured ObjectMapper customize the process.

Accept uploads as MultipartFile and validate size, type, and filename. For downloads, return a Resource or byte stream with suitable content type and Content-Disposition headers. Store files outside the application package.