[MM’s] Boot Notes — RestTemplate to RestClient to WebClient: Evolving HTTP in Spring 7

[MM’s] Boot Notes – RestTemplate to RestClient to WebClient: Evolving HTTP in Spring 7

From Deprecation to Migration: Everything You Need to Know About RestClient, WebClient, and RestTestClient.

The HTTP Client Evolution You Can’t Ignore

If you’ve been building REST integrations with Spring for years, chances are your development stack still includes RestTemplate — the long-time preferred way for HTTP calls. But times have changed.

With Spring Framework 7 and Spring Boot 4, the RestTemplate begins its deprecation path (announcement in 7.0, deprecated in 7.1, removed in 8.0) and the Spring team is recommending its modern successor: RestClient.

Meanwhile, WebClient remains the reactive powerhouse for high-performance and asynchronous use cases. The result — A simpler, clearer HTTP story for Spring developers.

⚡ TL;DR (Quick Recap)

RestTemplate → deprecation path (announcement in 7.0, deprecated in 7.1, removed in 8.0)
RestClient → modern, fluent, synchronous API designed for today’s Spring MVC apps.
WebClient → still the best choice for reactive or streaming workloads.
RestTestClient → new in Spring 7 for testing APIs with the same fluent style.

For over a decade, RestTemplate has been the default way to make HTTP calls in Spring applications. It’s been reliable, familiar and easy to use.

The Java platform has moved forward (with Java 17+, Virtual Threads, Structured Concurrency) and Spring’s own shift toward fluent and declarative APIs made RestTemplate’s template-style approach harder to maintain.

Spring Framework 7 marks the official transition: RestTemplate will be deprecated and RestClient is the new standard for synchronous HTTP communication.

RestTemplate: The Legacy Workhorse

RestTemplate has long been the go-to for blocking HTTP calls. It’s simple, synchronous and integrates well with traditional Spring MVC stacks.

var restTemplate = new RestTemplateBuilder().build();
var response = restTemplate.getForEntity(baseUrl() + "/" + demoId, Demo.class);

What developers loved about it

Simple and intuitive API
Works great in traditional MVC apps
Easy to use for quick REST calls

What held it back

Entirely blocking (bad for scalability)
Dozens of overloaded methods (no fluent flow)
Hard to extend for new features like API versioning or structured concurrency
Lacked modern observability and streaming support

RestTemplate did its job well — but its design simply couldn’t keep up with modern application demands.

RestClient: The Modern Successor

Introduced in Spring 6.1 and refined in Spring 7, RestClient delivers a fluent, composable and future-proof API for synchronous HTTP operations.

var restClient = RestClient.builder().build();
var retrieved = restClient
   .get()
   .uri(baseUrl() + "/" + demoId)
   .retrieve()
   .body(Demo.class);

Why developers love RestClient

Fluent and chainable syntax (no more overload clutter)
Easy configuration of base URLs, headers, and interceptors
Supports Virtual Threads (Java 21+)
Shares infrastructure with WebClient and RestTemplate
Integrated with Spring Boot 4’s new auto-configuration

var client = RestClient.builder()
    .baseUrl(baseUrl())
    .defaultHeader("Authorization", "Bearer token")
    .requestInterceptor((req, body, exec) -> {
        System.out.println("Requesting: " + req.getURI());
        return exec.execute(req, body);
    })
    .build();

Custom error handling

var response = client.get()
    .uri("/demos")
    .retrieve()
    .onStatus(HttpStatusCode::is4xxClientError, (req, res) -> {
        throw new IllegalStateException("Client error: " + res.getStatusCode());
    })
    .body(Demo.class);

RestClient keeps everything you liked about RestTemplate — but with a much cleaner, modern developer experience.

WebClient: The Reactive Powerhouse

If your app deals with high concurrency, streaming APIs or needs non-blocking I/O, WebClient remains the tool you can count on.

It’s fully reactive, built on Project Reactor and supports both Mono and Flux types for async data handling.

var webClient = WebClient.create(baseUrl());
var result = webClient.get()
    .uri("/demos")
    .retrieve()
    .bodyToMono(Demo.class)
    .block();

Why developers choose WebClient

Non-blocking, high-concurrency performance
Supports streaming (SSE, backpressure, etc.)
Integrates naturally with reactive stacks
Ideal for microservices and real-time APIs

When to use WebClient

You’re already using WebFlux or Project Reactor
You need to process streaming data or handle thousands of concurrent calls
You want async capabilities with minimal thread usage

Choosing the Right HTTP Client in Spring 7

Use RestClient when:

Building traditional MVC or servlet-based apps
You need synchronous calls with modern APIs
Migrating from RestTemplate
Working with Virtual Threads (Java 21+)
You DON’T need reactive streams or high concurrency

Use WebClient when:

Your app is built on WebFlux or uses reactive streams
You need non-blocking, streaming, or high-concurrency support
Handling 1000+ concurrent requests
Streaming data (SSE, WebSockets)
You need backpressure handling
Building reactive microservices

Avoid RestTemplate when:

Starting new projects (it’s deprecated)
You need advanced configuration, observability, or API versioning

Migration Tips: From RestTemplate to RestClient

Migrating to RestClient is straightforward — method calls translate cleanly with minimal effort.

GET Example (Before and After)

var response = restTemplate.getForObject(baseUrl(), Demo.class);
var response = restClient.get()
    .uri("/demos")
    .retrieve()
    .body(Demo.class);

POST Example (Before and After)

var response = restTemplate.postForEntity(
    baseUrl(), user, Void.class);

var response = restClient.post()
    .uri(baseUrl())
    .body(user)
    .retrieve()
    .toBodilessEntity();

Pro Tip:
You can wrap an existing RestTemplate to create a RestClient instance and migrate incrementally:

var restTemplate = new RestTemplate();
var restClient = RestClient.create(restTemplate);

Migration Complexity Considerations

Simple REST calls migrate easily, but watch out for:

Custom error handlers requiring refactoring
Complex interceptor chains needing redesign
Test code using TestRestTemplate (migrate to RestTestClient)
Libraries that internally use RestTemplate

Testing with RestTestClient (New in Spring 7)

Spring Framework 7 introduces RestTestClient, the new standard for testing HTTP endpoints in Spring MVC.
It unifies live-server and mock-based testing with a fluent, RestClient-style API.

var client = RestTestClient.bindToServer().baseUrl(baseUrl()).build();
client.get()
    .uri("/demos")
    .exchange()
    .expectStatus().isOk()
    .expectBody(String.class).isEqualTo("success");

Why it matters

Replaces TestRestTemplate
Uses the same fluent API as RestClient
Works across live and mock test scenarios

The Future of HTTP in Spring

Spring 7 defines a clean, consistent HTTP story moving forward:

RestTemplate → deprecated and phased out by Spring 8
RestClient → modern, fluent, synchronous HTTP client
WebClient → reactive and non-blocking client for advanced use cases
RestTestClient → unified testing experience for HTTP endpoints

This simplification means less confusion, better performance, and a cleaner developer experience across the Spring ecosystem.

Final Thoughts

Spring Framework 7 isn’t just another version — it’s a modernization of how we interact with HTTP in Java.
With RestClient, you get a clean, powerful API for synchronous communication.
With WebClient, you can handle asynchronous and streaming workloads at scale.

RestTemplate’s time has come to an end — but its successor brings a much better world for developers.

In short:

RestTemplate had a great run.
RestClient is the new standard.
WebClient remains the reactive powerhouse.

You can find all the code on GitHub.

Originally posted on marconak-matej.medium.com.

[MM’s] Boot Notes — RestTemplate to RestClient to WebClient: Evolving HTTP in Spring 7