Spring Web MVC Advanced
Deep Knowledge: Use mcp__documentation__fetch_docs with technology: spring-web for comprehensive documentation.
Quick Start
@RestController @RequestMapping("/api/v1") @RequiredArgsConstructor public class ApiController {
private final RestClient restClient;
@GetMapping("/proxy/{id}")
public ResponseEntity<Resource> proxyRequest(@PathVariable Long id) {
return restClient.get()
.uri("/external/resource/{id}", id)
.retrieve()
.toEntity(Resource.class);
}
}
@Configuration public class RestClientConfig {
@Bean
public RestClient restClient(RestClient.Builder builder) {
return builder
.baseUrl("https://api.external.com")
.defaultHeader(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
.connectTimeout(Duration.ofSeconds(5))
.readTimeout(Duration.ofSeconds(30))
.build();
}
}
RestClient Essentials (Spring 6.1+)
RestClient is the new synchronous HTTP client replacing RestTemplate.
@Service @RequiredArgsConstructor public class UserApiClient {
private final RestClient restClient;
// GET
public UserDto getUser(Long id) {
return restClient.get()
.uri("/users/{id}", id)
.retrieve()
.body(UserDto.class);
}
// POST
public UserDto createUser(CreateUserRequest request) {
return restClient.post()
.uri("/users")
.body(request)
.retrieve()
.body(UserDto.class);
}
// With error handling
public UserDto getUserSafe(Long id) {
return restClient.get()
.uri("/users/{id}", id)
.retrieve()
.onStatus(HttpStatusCode::is4xxClientError, (req, res) -> {
throw new ResourceNotFoundException("User not found: " + id);
})
.body(UserDto.class);
}
}
Full Reference: See http-clients.md for complete RestClient and WebClient documentation.
ResponseEntity Quick Patterns
@RestController @RequestMapping("/api/v1/users") public class UserController {
// Created with Location
@PostMapping
public ResponseEntity<UserResponse> create(
@Valid @RequestBody CreateUserRequest req,
UriComponentsBuilder uriBuilder) {
UserResponse created = service.create(req);
URI location = uriBuilder.path("/api/v1/users/{id}")
.buildAndExpand(created.getId()).toUri();
return ResponseEntity.created(location).body(created);
}
// With ETag
@GetMapping("/{id}")
public ResponseEntity<UserResponse> get(@PathVariable Long id) {
UserResponse user = service.findById(id);
return ResponseEntity.ok()
.eTag("\"" + user.getVersion() + "\"")
.cacheControl(CacheControl.maxAge(60, TimeUnit.SECONDS))
.body(user);
}
// No Content
@DeleteMapping("/{id}")
public ResponseEntity<Void> delete(@PathVariable Long id) {
service.delete(id);
return ResponseEntity.noContent().build();
}
}
Full Reference: See patterns.md for ResponseEntity, Content Negotiation, and Streaming.
File Upload/Download Quick Start
// Upload @PostMapping("/upload") public ResponseEntity<FileResponse> upload(@RequestParam("file") MultipartFile file) { String fileName = storageService.store(file); return ResponseEntity.ok(new FileResponse(fileName, file.getSize())); }
// Download @GetMapping("/download/{fileName}") public ResponseEntity<Resource> download(@PathVariable String fileName) { Resource resource = storageService.loadAsResource(fileName); return ResponseEntity.ok() .contentType(MediaType.APPLICATION_OCTET_STREAM) .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename="" + fileName + """) .body(resource); }
Full Reference: See file-handling.md for complete file operations.
Interceptors Quick Start
@Slf4j @Component public class LoggingInterceptor implements HandlerInterceptor {
@Override
public boolean preHandle(HttpServletRequest request,
HttpServletResponse response, Object handler) {
MDC.put("requestId", UUID.randomUUID().toString());
request.setAttribute("startTime", System.currentTimeMillis());
log.info("==> {} {}", request.getMethod(), request.getRequestURI());
return true;
}
@Override
public void afterCompletion(HttpServletRequest request,
HttpServletResponse response,
Object handler, Exception ex) {
long duration = System.currentTimeMillis() -
(Long) request.getAttribute("startTime");
log.info("<== {} ({} ms)", response.getStatus(), duration);
MDC.clear();
}
}
@Configuration public class WebConfig implements WebMvcConfigurer { @Override public void addInterceptors(InterceptorRegistry registry) { registry.addInterceptor(loggingInterceptor).addPathPatterns("/api/**"); } }
Full Reference: See advanced.md for Interceptors, Argument Resolvers, Exception Handling, and Testing.
Best Practices
Do Don't
Use RestClient for sync calls (Spring 3.2+) Use deprecated RestTemplate
Configure explicit timeouts Rely on default timeouts
Implement retry with exponential backoff Retry immediately without delay
Use interceptors for centralized logging Log in each method
Wrap responses in ResponseEntity Return raw objects
When NOT to Use This Skill
-
Reactive applications - Use spring-webflux skill
-
Basic REST controllers - Use spring-rest skill
-
WebSocket communication - Use spring-websocket skill
-
GraphQL APIs - Use spring-graphql skill
Anti-Patterns
Anti-Pattern Problem Solution
Using RestTemplate Deprecated, not type-safe Use RestClient (sync) or WebClient (async)
No timeout configuration Requests hang indefinitely Configure connect/read timeout
Memory leak with streams Stream not closed Use try-with-resources
N+1 HTTP calls Calls in loop Use batch endpoints or parallel calls
Blocking in WebFlux .block() in reactive stack Keep chain reactive
Quick Troubleshooting
Problem Diagnostic Fix
Connection timeout Check network/firewall Configure proper timeout values
SSL handshake fails Check certificates Configure SSLContext properly
Response not mapped Check Content-Type Configure message converters
Interceptor not called Check registration Verify interceptor order
File upload fails Check size limits Configure multipart settings
Reference Files
File Content
http-clients.md RestClient, WebClient, Interceptors
patterns.md ResponseEntity, Content Negotiation, Streaming
file-handling.md File Upload, Download, Storage Service
advanced.md Argument Resolvers, HandlerInterceptors, Exception Handling, Testing
External Documentation
-
Spring Web MVC
-
RestClient
-
WebClient