🧵 THREAD: RestClient vs WebClient vs RestTemplate. These three names get thrown around constantly in Spring discussions, but they are not interchangeable, and choosing the wrong one creates unnecessary complexity fast.

At the top level, there are two programming models. RestClient and RestTemplate are synchronous clients, while WebClient is a reactive, non-blocking option.

RestClient is the modern default for imperative Spring code. It gives you the fluent style people like in WebClient, but stays in the blocking model. Spring Boot explicitly points to it when you are not building a reactive WebFlux application.

WebClient provides a non-blocking, reactive API for making HTTP requests. It makes sense when the app is reactive, when you need streaming, or when outbound calls are part of a non-blocking pipeline and you actually want that model end to end.

RestTemplate is still around and still works, but it is no longer where Spring’s HTTP client story is moving. In current Spring docs, RestClient is positioned as the modern synchronous API, with RestTemplate deprecated in favor of it.

That makes new code and existing code two different decisions. If you want a modern alternative to RestTemplate, RestClient is the clean first choice. In a codebase already built around RestTemplate, the question is usually maintainability and consistency, not urgent migration.

The common mistake is reaching for WebClient just because it sounds cooler. If the rest of the app is blocking and downstream calls are plain request-response, you may just be adding a second mental model without getting much back.

A practical split is pretty simple. In a Spring MVC app with blocking downstream calls, start with RestClient. In a real WebFlux app or a genuinely reactive flow, use WebClient. In existing RestTemplate code, keep it stable unless there is a concrete reason to modernize.

There is one more piece worth knowing about: HTTP service interfaces. If you want a typed client API instead of building requests by hand, Spring can generate a proxy backed by either RestClient or WebClient.

So the practical takeaway is: use RestClient for new blocking code, WebClient when the reactive model is actually the point, and leave stable RestTemplate code alone unless you have a concrete reason to modernize it.