From 441b14b0c1405688a9f3101cf039a352cc9ec147 Mon Sep 17 00:00:00 2001
From: rstoyanchev <rossen.stoyanchev@broadcom.com>
Date: Fri, 29 Aug 2025 16:02:14 +0300
Subject: [PATCH] Handle error responses in RestClientAdapter

Closes gh-35375
---
 .../web/client/support/RestClientAdapter.java | 41 +++++++++++++------
 .../support/RestClientAdapterTests.java       | 11 +++++
 2 files changed, 39 insertions(+), 13 deletions(-)

diff --git a/spring-web/src/main/java/org/springframework/web/client/support/RestClientAdapter.java b/spring-web/src/main/java/org/springframework/web/client/support/RestClientAdapter.java
index af979f08eeb..d58fac3a0a5 100644
--- a/spring-web/src/main/java/org/springframework/web/client/support/RestClientAdapter.java
+++ b/spring-web/src/main/java/org/springframework/web/client/support/RestClientAdapter.java
@@ -16,6 +16,7 @@
 
 package org.springframework.web.client.support;
 
+import java.io.IOException;
 import java.io.InputStream;
 import java.net.URI;
 import java.util.ArrayList;
@@ -72,13 +73,10 @@ public final class RestClientAdapter implements HttpExchangeAdapter {
 		return newRequest(values).retrieve().toBodilessEntity().getHeaders();
 	}
 
-	@SuppressWarnings("unchecked")
 	@Override
 	public <T> @Nullable T exchangeForBody(HttpRequestValues values, ParameterizedTypeReference<T> bodyType) {
-		if (bodyType.getType().equals(InputStream.class)) {
-			return (T) newRequest(values).exchange((request, response) -> response.getBody(), false);
-		}
-		return newRequest(values).retrieve().body(bodyType);
+		return (bodyType.getType().equals(InputStream.class) ?
+				exchangeForInputStream(values) : newRequest(values).retrieve().body(bodyType));
 	}
 
 	@Override
@@ -86,16 +84,23 @@ public final class RestClientAdapter implements HttpExchangeAdapter {
 		return newRequest(values).retrieve().toBodilessEntity();
 	}
 
-	@SuppressWarnings("unchecked")
 	@Override
 	public <T> ResponseEntity<T> exchangeForEntity(HttpRequestValues values, ParameterizedTypeReference<T> bodyType) {
-		if (bodyType.getType().equals(InputStream.class)) {
-			return (ResponseEntity<T>) newRequest(values).exchangeForRequiredValue((request, response) ->
-					ResponseEntity.status(response.getStatusCode())
-							.headers(response.getHeaders())
-							.body(response.getBody()), false);
-		}
-		return newRequest(values).retrieve().toEntity(bodyType);
+		return (bodyType.getType().equals(InputStream.class) ?
+				exchangeForEntityInputStream(values) : newRequest(values).retrieve().toEntity(bodyType));
+	}
+
+	@SuppressWarnings("unchecked")
+	private <T> T exchangeForInputStream(HttpRequestValues values) {
+		return (T) newRequest(values).exchange((request, response) -> getInputStream(response), false);
+	}
+
+	@SuppressWarnings("unchecked")
+	private <T> ResponseEntity<T> exchangeForEntityInputStream(HttpRequestValues values) {
+		return (ResponseEntity<T>) newRequest(values).exchangeForRequiredValue((request, response) ->
+				ResponseEntity.status(response.getStatusCode())
+						.headers(response.getHeaders())
+						.body(getInputStream(response)), false);
 	}
 
 	@SuppressWarnings("unchecked")
@@ -157,6 +162,16 @@ public final class RestClientAdapter implements HttpExchangeAdapter {
 		return bodySpec;
 	}
 
+	private static InputStream getInputStream(
+			RestClient.RequestHeadersSpec.ConvertibleClientHttpResponse response) throws IOException {
+
+		if (response.getStatusCode().isError()) {
+			throw response.createException();
+		}
+		return response.getBody();
+	}
+
+
 
 	/**
 	 * Create a {@link RestClientAdapter} for the given {@link RestClient}.
diff --git a/spring-web/src/test/java/org/springframework/web/client/support/RestClientAdapterTests.java b/spring-web/src/test/java/org/springframework/web/client/support/RestClientAdapterTests.java
index b288a6e6591..648accfd3f9 100644
--- a/spring-web/src/test/java/org/springframework/web/client/support/RestClientAdapterTests.java
+++ b/spring-web/src/test/java/org/springframework/web/client/support/RestClientAdapterTests.java
@@ -56,6 +56,7 @@ import org.springframework.web.bind.annotation.RequestHeader;
 import org.springframework.web.bind.annotation.RequestParam;
 import org.springframework.web.bind.annotation.RequestPart;
 import org.springframework.web.client.ApiVersionInserter;
+import org.springframework.web.client.HttpClientErrorException;
 import org.springframework.web.client.RestClient;
 import org.springframework.web.client.RestTemplate;
 import org.springframework.web.multipart.MultipartFile;
@@ -69,6 +70,7 @@ import org.springframework.web.util.DefaultUriBuilderFactory;
 import org.springframework.web.util.UriBuilderFactory;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 /**
  * Integration tests for {@link HttpServiceProxyFactory} with {@link RestClient}
@@ -335,6 +337,15 @@ class RestClientAdapterTests {
 		assertThat(StreamUtils.copyToString(inputStream, StandardCharsets.UTF_8)).isEqualTo("Hello Spring 2!");
 	}
 
+	@Test // gh-35375
+	void getInputStreamWithError() {
+		prepareResponse(builder -> builder.code(400).body("rejected"));
+
+		assertThatThrownBy(() -> initService().getInputStream())
+				.isExactlyInstanceOf(HttpClientErrorException.BadRequest.class)
+				.hasMessage("400 Client Error: \"rejected\"");
+	}
+
 	@Test
 	void postOutputStream() throws Exception {
 		prepareResponse(builder ->