Wrap exceptions in WebClient

This commit makes sure that exceptions emitted by WebClient are wrapped
by WebClientExceptions:

- Exceptions emitted by the ClientHttpConnector are wrapped in a new
  WebClientRequestException.

- Exceptions emitted after a response is received are wrapped in a
  WebClientResponseException

Closes gh-23842

spring-webflux/src/test/java/org/springframework/web/reactive/function/client/WebClientDataBufferAllocatingTests.java

@@ -40,7 +40,6 @@ import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
 import org.springframework.http.client.reactive.ReactorClientHttpConnector;
 import org.springframework.http.client.reactive.ReactorResourceFactory;
-import org.springframework.web.reactive.function.UnsupportedMediaTypeException;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.TestInstance.Lifecycle.PER_CLASS;
@@ -127,7 +126,7 @@ class WebClientDataBufferAllocatingTests extends AbstractDataBufferAllocatingTes
 				.retrieve()
 				.bodyToMono(new ParameterizedTypeReference<Map<String, String>>() {});
 
-		StepVerifier.create(mono).expectError(UnsupportedMediaTypeException.class).verify(Duration.ofSeconds(3));
+		StepVerifier.create(mono).expectError(WebClientResponseException.class).verify(Duration.ofSeconds(3));
 		assertThat(this.server.getRequestCount()).isEqualTo(1);
 	}
 

spring-webflux/src/test/java/org/springframework/web/reactive/function/client/WebClientIntegrationTests.java

@@ -1013,7 +1013,12 @@ class WebClientIntegrationTests {
 		Mono<ClientResponse> responseMono = WebClient.builder().build().get().uri(uri).exchange();
 
 		StepVerifier.create(responseMono)
-				.expectErrorMessage("URI is not absolute: " + uri)
+				.expectErrorSatisfies(throwable -> {
+					assertThat(throwable).isInstanceOf(WebClientRequestException.class);
+					WebClientRequestException ex = (WebClientRequestException) throwable;
+					assertThat(ex.getMethod()).isEqualTo(HttpMethod.GET);
+					assertThat(ex.getUri()).isEqualTo(URI.create(uri));
+				})
 				.verify(Duration.ofSeconds(5));
 	}
 
@@ -1126,6 +1131,25 @@ class WebClientIntegrationTests {
 		expectRequestCount(1);
 	}
 
+	@ParameterizedWebClientTest
+	void invalidDomain(ClientHttpConnector connector) {
+		startServer(connector);
+
+		String url = "http://example.invalid";
+		Mono<ClientResponse> result = this.webClient.get().
+				uri(url)
+				.exchange();
+
+		StepVerifier.create(result)
+				.expectErrorSatisfies(throwable -> {
+					assertThat(throwable).isInstanceOf(WebClientRequestException.class);
+					WebClientRequestException ex = (WebClientRequestException) throwable;
+					assertThat(ex.getMethod()).isEqualTo(HttpMethod.GET);
+					assertThat(ex.getUri()).isEqualTo(URI.create(url));
+				})
+				.verify();
+	}
+
 
 	private void prepareResponse(Consumer<MockResponse> consumer) {
 		MockResponse response = new MockResponse();