Add docs on exceptions for HTTP interface client

Closes gh-28533

Author: rstoyanchev

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/support/WebClientAdapter.java

@@ -25,7 +25,6 @@
 import org.springframework.http.HttpMethod;
 import org.springframework.http.ResponseEntity;
 import org.springframework.util.Assert;
-import org.springframework.web.reactive.function.client.ClientResponse;
 import org.springframework.web.reactive.function.client.WebClient;
 import org.springframework.web.service.invoker.HttpClientAdapter;
 import org.springframework.web.service.invoker.HttpRequestValues;
@@ -57,41 +56,41 @@ private WebClientAdapter(WebClient webClient) {
 
 	@Override
 	public Mono<Void> requestToVoid(HttpRequestValues requestValues) {
-		return toBodySpec(requestValues).exchangeToMono(ClientResponse::releaseBody);
+		return newRequest(requestValues).retrieve().toBodilessEntity().then();
 	}
 
 	@Override
 	public Mono<HttpHeaders> requestToHeaders(HttpRequestValues requestValues) {
-		return toBodySpec(requestValues).retrieve().toBodilessEntity().map(ResponseEntity::getHeaders);
+		return newRequest(requestValues).retrieve().toBodilessEntity().map(ResponseEntity::getHeaders);
 	}
 
 	@Override
 	public <T> Mono<T> requestToBody(HttpRequestValues requestValues, ParameterizedTypeReference<T> bodyType) {
-		return toBodySpec(requestValues).retrieve().bodyToMono(bodyType);
+		return newRequest(requestValues).retrieve().bodyToMono(bodyType);
 	}
 
 	@Override
 	public <T> Flux<T> requestToBodyFlux(HttpRequestValues requestValues, ParameterizedTypeReference<T> bodyType) {
-		return toBodySpec(requestValues).retrieve().bodyToFlux(bodyType);
+		return newRequest(requestValues).retrieve().bodyToFlux(bodyType);
 	}
 
 	@Override
 	public Mono<ResponseEntity<Void>> requestToBodilessEntity(HttpRequestValues requestValues) {
-		return toBodySpec(requestValues).retrieve().toBodilessEntity();
+		return newRequest(requestValues).retrieve().toBodilessEntity();
 	}
 
 	@Override
 	public <T> Mono<ResponseEntity<T>> requestToEntity(HttpRequestValues requestValues, ParameterizedTypeReference<T> bodyType) {
-		return toBodySpec(requestValues).retrieve().toEntity(bodyType);
+		return newRequest(requestValues).retrieve().toEntity(bodyType);
 	}
 
 	@Override
 	public <T> Mono<ResponseEntity<Flux<T>>> requestToEntityFlux(HttpRequestValues requestValues, ParameterizedTypeReference<T> bodyType) {
-		return toBodySpec(requestValues).retrieve().toEntityFlux(bodyType);
+		return newRequest(requestValues).retrieve().toEntityFlux(bodyType);
 	}
 
 	@SuppressWarnings("ReactiveStreamsUnusedPublisher")
-	private WebClient.RequestBodySpec toBodySpec(HttpRequestValues requestValues) {
+	private WebClient.RequestBodySpec newRequest(HttpRequestValues requestValues) {
 
 		HttpMethod httpMethod = requestValues.getHttpMethod();
 		Assert.notNull(httpMethod, "HttpMethod is required");

src/docs/asciidoc/integration.adoc

@@ -371,7 +371,7 @@ methods for HTTP exchanges. You can then generate a proxy that implements this i
 and performs the exchanges. This helps to simplify HTTP remote access which often
 involves a facade that wraps the details of using the underlying HTTP client.
 
-To start, declare an interface with annotated, HTTP exchange methods:
+One, declare an interface with `@HttpExchange` methods:
 
 [source,java,indent=0,subs="verbatim,quotes"]
 ----
@@ -385,8 +385,7 @@ To start, declare an interface with annotated, HTTP exchange methods:
 	}
 ----
 
-Now you create a proxy for the interface that performs the declared exchanges through
-the `WebClient`:
+Two, create a proxy that will perform the declared HTTP exchanges:
 
 [source,java,indent=0,subs="verbatim,quotes"]
 ----
@@ -396,7 +395,7 @@ the `WebClient`:
 	RepositoryService service = factory.createClient(RepositoryService.class);
 ----
 
-An HTTP service interface can declare common attributes at the type level:
+`@HttpExchange` is supported at the type level where it applies to all methods:
 
 [source,java,indent=0,subs="verbatim,quotes"]
 ----
@@ -504,6 +503,27 @@ TIP: You can also use any other async or reactive types registered in the
 `ReactiveAdapterRegistry`.
 
 
+[[rest-http-interface-exceptions]]
+==== Exception Handling
+
+By default, `WebClient` raises `WebClientResponseException` for 4xx and 5xx HTTP status
+codes. To customize this, you can register a response status handler that applies to all
+responses performed through the client:
+
+[source,java,indent=0,subs="verbatim,quotes"]
+----
+	WebClient webClient = WebClient.builder()
+			.defaultStatusHandler(HttpStatusCode::isError, resp -> ...)
+			.build();
+
+	HttpServiceProxyFactory proxyFactory =
+			WebClientAdapter.createHttpServiceProxyFactory(webClient);
+----
+
+For more details and options, such as suppressing error status codes, see the Javadoc of
+`defaultStatusHandler` in `WebClient.Builder`.
+
+
 
 
 [[jms]]