Spring6提供的四种远程接口调用神器！你知道那种？

RestTemplate template = new RestTemplate(new HttpComponentsClientHttpRequestFactory());

String result = restTemplate.getForObject(
    "http://pack.com/users/{userId}", String.class, 666) ;

Map<String, Object> params = Collections.singletonMap("userId", 666);


String result = restTemplate.getForObject(
    "http://pack.com/users/{userId}", String.class, params) ;

String uriTemplate = "http://pack.com/users/{userId}";
URI uri = UriComponentsBuilder.fromUriString(uriTemplate).build(42);


RequestEntity<Void> requestEntity = RequestEntity.get(uri)
    .header("x-api-token", "aabbcc")
    .build() ;
ResponseEntity<String> response = template.exchange(requestEntity, String.class);
String responseHeader = response.getHeaders().getFirst("x-version");
String body = response.getBody() ;

User user = restTemplate.getForObject("http://pack.com/users/{userId}", User.class, 666);

public RestTemplate() {
  this.messageConverters.add(new ByteArrayHttpMessageConverter());
  this.messageConverters.add(new StringHttpMessageConverter());
  this.messageConverters.add(new ResourceHttpMessageConverter(false));
  // ...其它转换器
  if (jackson2Present) {
    this.messageConverters.add(new MappingJackson2HttpMessageConverter());
  }
  else if (gsonPresent) {
    this.messageConverters.add(new GsonHttpMessageConverter());
  }
  else if (jsonbPresent) {
    this.messageConverters.add(new JsonbHttpMessageConverter());
  }
  // ...其它转换器
  this.uriTemplateHandler = initUriTemplateHandler();
}

Mono<Person> result = client.get()
  .uri("/users/{userId}", id).accept(MediaType.APPLICATION_JSON)
  .retrieve()
  .bodyToMono(User.class);

@HttpExchange(url = "/demos")
public interface DemoInterface {


  @PostExchange("/format3/{id}")
  Users queryUser(@PathVariable Long id);


}

@Service
public class DemoService {


  private final DemoInterface demoInterface ;


  public DemoService() {
    // 基于响应式调用；你当前的环境需要引入webflux
    WebClient client = WebClient.builder().baseUrl("http://localhost:8088/").build() ;
    HttpServiceProxyFactory factory = HttpServiceProxyFactory.builder(WebClientAdapter.forClient(client)).build() ;
    this.demoInterface = factory.createClient(DemoInterface.class) ;
  }


  public Users queryUser(Long id) {
    return this.demoInterface.queryUser(id) ;
  }


}

@Resource
private DemoService demoService ;




@GetMapping("/{id}")
public Users getUser(@PathVariable("id") Long id) {
  return this.demoService.queryUser(id) ;
}

WebClient client = WebClient.builder()
    // 状态码为4xx或5xx
    .defaultStatusHandler(HttpStatusCode::isError, resp -> Mono.just(new RuntimeException(resp.statusCode().toString() + "请求错误")))
    .baseUrl("http://localhost:8088/").build() ;
HttpServiceProxyFactory factory = HttpServiceProxyFactory
    .builder(WebClientAdapter.forClient(client)).build() ;

// 默认通过静态方法创建
RestClient restClient = RestClient.create();
// 自定义方式
RestClient restClient = RestClient.builder()
  .requestFactory(new HttpComponentsClientHttpRequestFactory())
  // 自定义消息转换器
  // .messageConverters(converters -> converters.add(new PackCustomMessageConverter()))
  .baseUrl("http://localhost:8088")
  .defaultUriVariables(Map.of("id", "888"))
  .defaultHeader("x-api-token", "aabbcc")
  .requestInterceptor(new ClientHttpRequestInterceptor() {
    @Override
    public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution)
        throws IOException {
      System.out.println("我是拦截器") ;
      return execution.execute(request, body) ;
    }
  })
  .requestInitializer(new ClientHttpRequestInitializer() {
    @Override
    public void initialize(ClientHttpRequest request) {
      System.out.println("我是初始化器") ;
      request.getHeaders().add("x-version", "1.0.0") ;
    }
  })
  .build() ;

Users users = customClient.get()
  .uri("/demos/users/{id}")
  .retrieve()
  .body(Users.class) ;

Users user = new Users();
ResponseEntity<Void> response = restClient.post() 
  .uri("/demos/users") 
  .contentType(APPLICATION_JSON) 
  .body(user) 
  .retrieve()
  .toBodilessEntity() ;

Users users = customClient.get()
  .uri("/demos/users/{id}")
  .retrieve()
  // 处理返回状态码为：4xx和5xx
  .onStatus(HttpStatusCode::isError, (request, response) -> {
    throw new RuntimeException(response.getStatusCode().toString() + "请求错误") ;
  })
  .body(Users.class) ;