java 41 lines · 8 steps

Declarative HTTP clients in Spring

An annotated interface becomes a live GitHub API client through Spring's HttpServiceProxyFactory.

Explained by highlit

Spring Intermediate http-client declarative-api proxy configuration rest

1public interface GitHubClient {
2 
3    @GetExchange("/users/{username}")
4    GitHubUser getUser(@PathVariable String username);
5 
6    @GetExchange("/users/{username}/repos")
7    List<Repository> listRepositories(@PathVariable String username,
8                                      @RequestParam(defaultValue = "updated") String sort,
9                                      @RequestParam(name = "per_page", defaultValue = "30") int perPage);
10 
11    @PostExchange("/user/repos")
12    Repository createRepository(@RequestHeader("Authorization") String bearerToken,
13                                @RequestBody CreateRepositoryRequest request);
14 
15    @DeleteExchange("/repos/{owner}/{repo}")
16    ResponseEntity<Void> deleteRepository(@PathVariable String owner, @PathVariable String repo);
17}
18 
19@Configuration
20class GitHubClientConfig {
21 
22    @Bean
23    GitHubClient gitHubClient(WebClient.Builder builder,
24                              @Value("${github.base-url:https://api.github.com}") String baseUrl,
25                              @Value("${github.token}") String token) {
26        WebClient webClient = builder
27                .baseUrl(baseUrl)
28                .defaultHeader(HttpHeaders.ACCEPT, "application/vnd.github+json")
29                .defaultHeader(HttpHeaders.AUTHORIZATION, "Bearer " + token)
30                .defaultHeader("X-GitHub-Api-Version", "2022-11-28")
31                .build();
32 
33        WebClientAdapter adapter = WebClientAdapter.create(webClient);
34 
35        HttpServiceProxyFactory factory = HttpServiceProxyFactory
36                .builderFor(adapter)
37                .build();
38 
39        return factory.createClient(GitHubClient.class);
40    }
41}

01 / 01

STEP 01

Walkthrough

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Three takeaways

1Spring can generate a working HTTP client from an interface, so you describe endpoints instead of writing request plumbing.
2Method annotations like @GetExchange and @PathVariable map Java signatures directly onto HTTP verbs, paths, and parameters.
3Centralizing base URL and auth headers in the WebClient keeps per-call methods clean and consistent.

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