Consistent handling of 4xx/5xx status codes in WebClient

This commit changes the handling of 4xx/5xx status codes in the
WebClient to the following simple rule: if there is no way for the user
to get the response status code, then a WebClientException is returned.
If there is a way to get to the status code, then we do not return an
exception.

Issue: SPR-15486

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

@@ -29,7 +29,6 @@ import org.junit.Before;
 import org.junit.Test;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
-import reactor.test.StepVerifier;
 
 import org.springframework.core.codec.StringDecoder;
 import org.springframework.core.io.buffer.DataBuffer;
@@ -48,7 +47,7 @@ import org.springframework.util.MultiValueMap;
 
 import static org.junit.Assert.*;
 import static org.mockito.Mockito.*;
-import static org.springframework.web.reactive.function.BodyExtractors.*;
+import static org.springframework.web.reactive.function.BodyExtractors.toMono;
 
 /**
  * @author Arjen Poutsma
@@ -151,24 +150,6 @@ public class DefaultClientResponseTests {
 		assertEquals("foo", resultMono.block());
 	}
 
-	@Test
-	public void bodyToMonoError() throws Exception {
-		HttpHeaders httpHeaders = new HttpHeaders();
-		httpHeaders.setContentType(MediaType.TEXT_PLAIN);
-		when(mockResponse.getHeaders()).thenReturn(httpHeaders);
-		when(mockResponse.getStatusCode()).thenReturn(HttpStatus.NOT_FOUND);
-
-		Set<HttpMessageReader<?>> messageReaders = Collections
-				.singleton(new DecoderHttpMessageReader<>(StringDecoder.allMimeTypes(true)));
-		when(mockExchangeStrategies.messageReaders()).thenReturn(messageReaders::stream);
-
-		Mono<String> resultMono = defaultClientResponse.bodyToMono(String.class);
-
-		StepVerifier.create(resultMono)
-				.expectError(WebClientException.class)
-				.verify();
-	}
-
 	@Test
 	public void bodyToFlux() throws Exception {
 		DefaultDataBufferFactory factory = new DefaultDataBufferFactory();
@@ -191,21 +172,4 @@ public class DefaultClientResponseTests {
 		assertEquals(Collections.singletonList("foo"), result.block());
 	}
 
-	@Test
-	public void bodyToFluxError() throws Exception {
-		HttpHeaders httpHeaders = new HttpHeaders();
-		httpHeaders.setContentType(MediaType.TEXT_PLAIN);
-		when(mockResponse.getHeaders()).thenReturn(httpHeaders);
-		when(mockResponse.getStatusCode()).thenReturn(HttpStatus.INTERNAL_SERVER_ERROR);
-
-		Set<HttpMessageReader<?>> messageReaders = Collections
-				.singleton(new DecoderHttpMessageReader<>(StringDecoder.allMimeTypes(true)));
-		when(mockExchangeStrategies.messageReaders()).thenReturn(messageReaders::stream);
-
-		Flux<String> resultFlux = defaultClientResponse.bodyToFlux(String.class);
-		StepVerifier.create(resultFlux)
-				.expectError(WebClientException.class)
-				.verify();
-	}
-
 }

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

@@ -334,7 +334,7 @@ public class WebClientIntegrationTests {
 	}
 
 	@Test
-	public void notFound() throws Exception {
+	public void exchangeNotFound() throws Exception {
 		this.server.enqueue(new MockResponse().setResponseCode(404)
 				.setHeader("Content-Type", "text/plain").setBody("Not Found"));
 
@@ -351,6 +351,47 @@ public class WebClientIntegrationTests {
 		Assert.assertEquals("/greeting?name=Spring", recordedRequest.getPath());
 	}
 
+	@Test
+	public void retrieveBodyToMonoNotFound() throws Exception {
+		this.server.enqueue(new MockResponse().setResponseCode(404)
+				.setHeader("Content-Type", "text/plain").setBody("Not Found"));
+
+		Mono<String> result = this.webClient.get()
+				.uri("/greeting?name=Spring")
+				.retrieve()
+				.bodyToMono(String.class);
+
+		StepVerifier.create(result)
+				.expectError(WebClientException.class)
+				.verify(Duration.ofSeconds(3));
+
+		RecordedRequest recordedRequest = server.takeRequest();
+		Assert.assertEquals(1, server.getRequestCount());
+		Assert.assertEquals("*/*", recordedRequest.getHeader(HttpHeaders.ACCEPT));
+		Assert.assertEquals("/greeting?name=Spring", recordedRequest.getPath());
+	}
+
+	@Test
+	public void retrieveToEntityNotFound() throws Exception {
+		this.server.enqueue(new MockResponse().setResponseCode(404)
+				.setHeader("Content-Type", "text/plain").setBody("Not Found"));
+
+		Mono<ResponseEntity<String>> result = this.webClient.get()
+				.uri("/greeting?name=Spring")
+				.retrieve()
+				.toEntity(String.class);
+
+		StepVerifier.create(result)
+				.consumeNextWith(response -> assertEquals(HttpStatus.NOT_FOUND, response.getStatusCode()))
+				.expectComplete()
+				.verify(Duration.ofSeconds(3));
+
+		RecordedRequest recordedRequest = server.takeRequest();
+		Assert.assertEquals(1, server.getRequestCount());
+		Assert.assertEquals("*/*", recordedRequest.getHeader(HttpHeaders.ACCEPT));
+		Assert.assertEquals("/greeting?name=Spring", recordedRequest.getPath());
+	}
+
 	@Test
 	public void buildFilter() throws Exception {
 		this.server.enqueue(new MockResponse().setHeader("Content-Type", "text/plain").setBody("Hello Spring!"));