Why RestTemplate Is Being Retired in Spring Boot 4.2 and How to Switch to RestClient

Deprecation in Spring Framework and Spring Boot 4.2

Spring Framework marks RestTemplate as deprecated and Spring Boot 4.2.0‑M1 deprecates RestTemplateAutoConfiguration, RestTemplateBuilder and TestRestTemplate.

Typical RestTemplate usage

UserResponse response = restTemplate.getForObject("http://user-service/api/users/{id}", UserResponse.class, userId);
ResponseEntity<PayResponse> response = restTemplate.postForEntity(url, request, PayResponse.class);

These synchronous calls fit a simple controller → service → HTTP call → wait → continue flow, so many projects kept using RestTemplate instead of the reactive WebClient.

RestClient as the synchronous successor

Spring positions the new client as:

RestClient   – synchronous, Fluent API
WebClient    – non‑blocking, Reactive
RestTemplate – old synchronous Template API, deprecated

RestClient retains a synchronous model while providing a fluent API, eliminating the need for reactive programming changes.

Interface conversion example

Original RestTemplate method:

public LogisticsResult query(String trackingNo) {
    String url = logisticsUrl + "/api/tracking/" + trackingNo;
    ResponseEntity<LogisticsResult> response = restTemplate.getForEntity(url, LogisticsResult.class);
    return response.getBody();
}

Converted to RestClient:

public LogisticsResult query(String trackingNo) {
    return restClient.get()
        .uri("/api/tracking/{trackingNo}", trackingNo)
        .retrieve()
        .body(LogisticsResult.class);
}

The fluent chain mirrors the actual HTTP request flow (method → URL → headers → body → send → response), improving readability.

Avoiding a global RestClient instance

Define a dedicated client per external system:

@Configuration
public class HttpClientConfig {
    @Bean
    RestClient logisticsRestClient(RestClient.Builder builder) {
        return builder.baseUrl("https://logistics.example.com")
            .defaultHeader(HttpHeaders.ACCEPT, MediaType.APPLICATION_JSON_VALUE)
            .requestInterceptor(new TraceIdInterceptor())
            .build();
    }
}

Business code injects RestClient logisticsRestClient without needing to know the domain, headers, tracing or the underlying HTTP client.

Separating HTTP errors from business errors

Map a specific HTTP status to a domain exception while letting other 5xx statuses follow a separate error‑handling path:

PayResponse response = restClient.post()
    .uri("/api/pay")
    .body(request)
    .retrieve()
    .onStatus(status -> status.value() == 409,
        (req, res) -> { throw new OrderAlreadyPaidException(); })
    .body(PayResponse.class);

Declarative HTTP Service Client

Define an interface annotated with @HttpExchange to generate an implementation automatically:

@HttpExchange("/users")
public interface UserClient {
    @GetExchange("/{id}")
    UserResponse getUser(@PathVariable Long id);
}

This built‑in capability replaces the need for an external @FeignClient dependency.

Gradual migration strategy

Convert low‑risk third‑party interfaces first.

Then migrate internal service calls.

Leave core payment/order flows for the final stage.

Spring allows creating a RestClient from an existing RestTemplate to retain configured request factories, interceptors and message converters:

RestClient restClient = RestClient.create(restTemplate);

After all calls are switched, the builder configuration can be cleaned up.

Testing with RestTestClient

Both RestTemplateBuilder and TestRestTemplate are deprecated. The recommended replacement is RestTestClient built on top of RestClient:

RestTestClient client = RestTestClient.bindToController(new OrderController(orderService)).build();
client.get().uri("/orders/10001").exchange()
    .expectStatus().isOk()
    .expectBody(OrderResponse.class);

It can test controllers without starting a real server or perform end‑to‑end tests against a live HTTP server.

Adoption guidance

If a project runs on Spring Boot 2.x or 3.x and RestTemplate works reliably, immediate massive refactoring is not required. New code should prefer RestClient (or the declarative @HttpExchange style) while existing code can be migrated incrementally.

For new projects or when upgrading to Spring Boot 4.x, create RestClient instances directly and consider the HTTP Service Client for declarative calls.

Spring Framework documentation states that RestTemplate is deprecated and will be removed in a future version, and Spring Boot 4.2 begins cleaning up its associated auto‑configuration and testing infrastructure.