Improvements to HTTP interfaces

December 1st, 2025

2 minute read

Spring Spring boot Advent of Spring

Introduction

Spring Boot 4 has been released last month! Considering all the new features it has, I decided to write about these features throughout the month of December. It will be an advent of Spring Boot 4 related tips!

One of the big features of Spring Boot 3 was the fluent RestClient and the capability of defining REST clients as interfaces by using the HTTP Exchange annotations. Spring Boot 4 extends on that by making it easier to bootstrap these HTTP interface beans.

What is an HTTP exchange interface

The HTTP exchange interface allowed you to define REST clients like this:

@HttpExchange("https://jsonplaceholder.typicode.com/posts")
public interface PostApiClient {
    @GetExchange
    List<Post> getPosts();
}

These interfaces still had to be initialized manually though by using a HttpServiceProxyFactory and binding them to either a RestClient or a reactive WebClient.

This looked something like this:

@Bean
RestClient jsonPlaceholderClient(RestClient.Builder builder) {
    return builder.build();
}

@Bean
PostApiClient postApiClient(RestClient jsonPlaceholderClient) {
    var factory = HttpServiceProxyFactory
        .builder()
        .exchangeAdapter(RestClientAdapter.create(jsonPlaceholderClient))
        .build();
    return factory.createClient(PostApiClient.class);
}

Improvements

With Spring Boot 4 on the other hand, we now get a convenient @ImportHttpServices annotation. With this annotation, we can simply include the interfaces we want to create beans for, and that’s it!

For example:

@Configuration
@ImportHttpServices(PostApiClient.class)
class RestClientConfiguration {
    
}

You might think, but what if I configured the base URL in my RestClient itself? Well, no worries. You can also define HTTP interface groups:

@Configuration
@ImportHttpServices(groups = "jsonplaceholder", types = {PostApiClient.class, CommentApiClient.class})
class RestClientConfiguration {
    
}

And now you can configure the base URL of this "jsonplaceholder" group by setting the following property:

spring.http.serviceclient.jsonplaceholder.base-url=https://jsonplaceholder.typicode.com

In case you need more advanced control over your RestClient, you can also programmatically configure the RestClient.Builder by defining a RestClientHttpServiceGroupConfigurer:

@Bean
RestClientHttpServiceGroupConfigurer groupConfigurer() {
    return groups -> {
        groups
            .filterByName("jsonplaceholder")
            .forEachClient((_, builder) ->
                builder.baseUrl("https://jsonplaceholder.typicode.com"));
    };
}

Conclusion

Spring Boot’s improvements to the HTTP exchange interfaces turn it into a very handy feature that makes me wonder how we survived this long without!

This blogpost is a part of the Advent of Spring Boot 2025 series.