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Spring Boot REST API Standards
Overview
REST API design standards for Spring Boot covering URL design, HTTP methods, status codes, DTOs, validation, error handling, pagination, and security headers.
When to Use
- Creating REST endpoints and API routes
- Designing DTOs and API contracts
- Implementing error handling and validation
- Setting up pagination and filtering
- Configuring security headers and CORS
- Reviewing REST API architecture
Instructions
To Build RESTful API Endpoints
Follow these steps to create well-designed REST API endpoints:
- Design Resource-Based URLs
- Use plural nouns for resource names
- Follow REST conventions: GET /users, POST /users, PUT /users/{id}
- Avoid action-based URLs like /getUserList
- Implement Proper HTTP Methods
- GET: Retrieve resources (safe, idempotent)
- POST: Create resources (not idempotent)
- PUT: Replace entire resources (idempotent)
- PATCH: Partial updates (not idempotent)
- DELETE: Remove resources (idempotent)
- Use Appropriate Status Codes
- 200 OK: Successful GET/PUT/PATCH
- 201 Created: Successful POST with Location header
- 204 No Content: Successful DELETE
- 400 Bad Request: Invalid request data
- 404 Not Found: Resource doesn't exist
- 409 Conflict: Duplicate resource
- 500 Internal Server Error: Unexpected errors
- Create Request/Response DTOs
- Separate API contracts from domain entities
- Use Java records or Lombok
@Data/@Value - Apply Jakarta validation annotations
- Keep DTOs immutable when possible
- Implement Validation
- Use
@Validannotation on@RequestBodyparameters - Apply validation constraints (
@NotBlank,@Email,@Size, etc.) - Handle validation errors with
MethodArgumentNotValidException
- Set Up Error Handling
- Use
@RestControllerAdvicefor global exception handling - Return standardized error responses with status, error, message, and timestamp
- Use
ResponseStatusExceptionfor specific HTTP status codes
- Configure Pagination
- Use Pageable for large datasets
- Include page, size, sort parameters
- Return metadata with total elements, totalPages, etc.
- Add Security Headers
- Configure CORS policies
- Set content security policy
- Include X-Frame-Options, X-Content-Type-Options
Validation checkpoints:
- After step 1-2: Verify URL structure follows REST conventions (/users not /getUsers)
- After step 3: Test each endpoint returns correct status codes
- After step 4-5: Validate DTOs with curl or HTTPie before proceeding
- After step 6: Confirm error responses match standardized format
Examples
Basic CRUD Controller
java
@RestController
@RequestMapping("/v1/users")
@RequiredArgsConstructor
@Slf4j
public class UserController {
private final UserService userService;
@GetMapping
public ResponseEntity<Page<UserResponse>> getAllUsers(
@RequestParam(defaultValue = "0") int page,
@RequestParam(defaultValue = "10") int pageSize) {
log.debug("Fetching users page {} size {}", page, pageSize);
Page<UserResponse> users = userService.getAll(page, pageSize);
return ResponseEntity.ok(users);
}
@GetMapping("/{id}")
public ResponseEntity<UserResponse> getUserById(@PathVariable Long id) {
return ResponseEntity.ok(userService.getById(id));
}
@PostMapping
public ResponseEntity<UserResponse> createUser(@Valid @RequestBody CreateUserRequest request) {
UserResponse created = userService.create(request);
return ResponseEntity.status(HttpStatus.CREATED).body(created);
}
@PutMapping("/{id}")
public ResponseEntity<UserResponse> updateUser(
@PathVariable Long id,
@Valid @RequestBody UpdateUserRequest request) {
return ResponseEntity.ok(userService.update(id, request));
}
@DeleteMapping("/{id}")
public ResponseEntity<Void> deleteUser(@PathVariable Long id) {
userService.delete(id);
return ResponseEntity.noContent().build();
}
}Request/Response DTOs
java
// Request DTO
@Data
@NoArgsConstructor
@AllArgsConstructor
public class CreateUserRequest {
@NotBlank(message = "User name cannot be blank")
private String name;
@Email(message = "Valid email required")
private String email;
}
// Response DTO
@Data
@NoArgsConstructor
@AllArgsConstructor
public class UserResponse {
private Long id;
private String name;
private String email;
private LocalDateTime createdAt;
}Global Exception Handler
java
@RestControllerAdvice
@Slf4j
public class GlobalExceptionHandler {
@ExceptionHandler(MethodArgumentNotValidException.class)
public ResponseEntity<ErrorResponse> handleValidationException(
MethodArgumentNotValidException ex, WebRequest request) {
String errors = ex.getBindingResult().getFieldErrors().stream()
.map(f -> f.getField() + ": " + f.getDefaultMessage())
.collect(Collectors.joining(", "));
ErrorResponse errorResponse = new ErrorResponse(
HttpStatus.BAD_REQUEST.value(),
"Validation Error",
"Validation failed: " + errors,
request.getDescription(false).replaceFirst("uri=", "")
);
return new ResponseEntity<>(errorResponse, HttpStatus.BAD_REQUEST);
}
@ExceptionHandler(ResponseStatusException.class)
public ResponseEntity<ErrorResponse> handleResponseStatusException(
ResponseStatusException ex, WebRequest request) {
ErrorResponse error = new ErrorResponse(
ex.getStatusCode().value(),
ex.getStatusCode().toString(),
ex.getReason(),
request.getDescription(false).replaceFirst("uri=", "")
);
return new ResponseEntity<>(error, ex.getStatusCode());
}
}Best Practices
1. Use Constructor Injection
java
@Service
@RequiredArgsConstructor
public class UserService {
private final UserRepository userRepository;
}2. Prefer Immutable DTOs (Java Records or @Value)
java
public record UserResponse(Long id, String name, String email) {}3. Implement Proper Transaction Management
java
@Service
@Transactional
public class UserService {
@Transactional(readOnly = true)
public Optional<User> findById(Long id) { return userRepository.findById(id); }
@Transactional
public User create(User user) { return userRepository.save(user); }
}Constraints and Warnings
- Never expose entities directly - Use DTOs to separate API contracts from domain models
- Follow REST conventions - Use nouns for resources (/users), correct HTTP methods, plural names, proper status codes
- Handle all exceptions globally - Use
@RestControllerAdvice, never let raw exceptions bubble up - Always paginate large result sets - Prevent performance issues and DDoS vulnerabilities
- Validate all input data - Use Jakarta validation annotations on request DTOs
- Never expose sensitive data - Don't log or expose passwords, tokens, PII
References
- See
references/directory for comprehensive reference material including HTTP status codes, Spring annotations, and detailed examples - Refer to the
developer-kit-java:spring-boot-code-review-expertagent for code review guidelines - Review
spring-boot-dependency-injection/SKILL.mdfor dependency injection patterns - Check
../spring-boot-test-patterns/SKILL.mdfor testing REST APIs
