Apply attributes to the underlying HTTP request

See gh-29958

spring-test/src/main/java/org/springframework/mock/http/client/reactive/MockClientHttpRequest.java

@@ -119,6 +119,10 @@ public class MockClientHttpRequest extends AbstractClientHttpRequest {
 				.forEach(cookie -> getHeaders().add(HttpHeaders.COOKIE, cookie.toString()));
 	}
 
+	@Override
+	protected void applyAttributes() {
+	}
+
 	@Override
 	public Mono<Void> writeWith(Publisher<? extends DataBuffer> body) {
 		return doCommit(() -> Mono.defer(() -> this.writeHandler.apply(Flux.from(body))));

spring-test/src/main/java/org/springframework/test/web/reactive/server/DefaultWebTestClientBuilder.java

@@ -94,6 +94,8 @@ class DefaultWebTestClientBuilder implements WebTestClient.Builder {
 	@Nullable
 	private MultiValueMap<String, String> defaultCookies;
 
+	private boolean applyAttributes;
+
 	@Nullable
 	private List<ExchangeFilterFunction> filters;
 
@@ -155,6 +157,7 @@ class DefaultWebTestClientBuilder implements WebTestClient.Builder {
 		}
 		this.defaultCookies = (other.defaultCookies != null ?
 				new LinkedMultiValueMap<>(other.defaultCookies) : null);
+		this.applyAttributes = other.applyAttributes;
 		this.filters = (other.filters != null ? new ArrayList<>(other.filters) : null);
 		this.entityResultConsumer = other.entityResultConsumer;
 		this.strategies = other.strategies;
@@ -213,6 +216,12 @@ class DefaultWebTestClientBuilder implements WebTestClient.Builder {
 		return this.defaultCookies;
 	}
 
+	@Override
+	public WebTestClient.Builder applyAttributes(boolean applyAttributes) {
+		this.applyAttributes = applyAttributes;
+		return this;
+	}
+
 	@Override
 	public WebTestClient.Builder filter(ExchangeFilterFunction filter) {
 		Assert.notNull(filter, "ExchangeFilterFunction is required");
@@ -312,22 +321,25 @@ class DefaultWebTestClientBuilder implements WebTestClient.Builder {
 				this.entityResultConsumer, this.responseTimeout, new DefaultWebTestClientBuilder(this));
 	}
 
-	private static ClientHttpConnector initConnector() {
+	private ClientHttpConnector initConnector() {
+		final ClientHttpConnector connector;
 		if (reactorNettyClientPresent) {
-			return new ReactorClientHttpConnector();
+			connector = new ReactorClientHttpConnector();
 		}
 		else if (reactorNetty2ClientPresent) {
 			return new ReactorNetty2ClientHttpConnector();
 		}
 		else if (jettyClientPresent) {
-			return new JettyClientHttpConnector();
+			connector = new JettyClientHttpConnector();
 		}
 		else if (httpComponentsClientPresent) {
-			return new HttpComponentsClientHttpConnector();
+			connector = new HttpComponentsClientHttpConnector();
 		}
 		else {
-			return new JdkClientHttpConnector();
+			connector = new JdkClientHttpConnector();
 		}
+		connector.setApplyAttributes(this.applyAttributes);
+		return connector;
 	}
 
 	private ExchangeStrategies initExchangeStrategies() {

spring-test/src/main/java/org/springframework/test/web/reactive/server/HttpHandlerConnector.java

@@ -64,6 +64,8 @@ public class HttpHandlerConnector implements ClientHttpConnector {
 
 	private final HttpHandler handler;
 
+	private boolean applyAttributes = true;
+
 
 	/**
 	 * Constructor with the {@link HttpHandler} to handle requests with.
@@ -82,6 +84,16 @@ public class HttpHandlerConnector implements ClientHttpConnector {
 				.subscribeOn(Schedulers.parallel());
 	}
 
+	@Override
+	public void setApplyAttributes(boolean applyAttributes) {
+		this.applyAttributes = applyAttributes;
+	}
+
+	@Override
+	public boolean getApplyAttributes() {
+		return this.applyAttributes;
+	}
+
 	private Mono<ClientHttpResponse> doConnect(
 			HttpMethod httpMethod, URI uri, Function<? super ClientHttpRequest, Mono<Void>> requestCallback) {
 

spring-test/src/main/java/org/springframework/test/web/reactive/server/WebTestClient.java

@@ -425,6 +425,13 @@ public interface WebTestClient {
 		 */
 		Builder defaultCookies(Consumer<MultiValueMap<String, String>> cookiesConsumer);
 
+		/**
+		 * Global option to specify whether or not attributes should be applied to every request,
+		 * if the used {@link ClientHttpConnector} allows it.
+		 * @param applyAttributes whether or not to apply attributes
+		 */
+		Builder applyAttributes(boolean applyAttributes);
+
 		/**
 		 * Add the given filter to the filter chain.
 		 * @param filter the filter to be added to the chain

spring-test/src/main/java/org/springframework/test/web/reactive/server/WiretapConnector.java

@@ -55,6 +55,8 @@ class WiretapConnector implements ClientHttpConnector {
 
 	private final Map<String, ClientExchangeInfo> exchanges = new ConcurrentHashMap<>();
 
+	private boolean applyAttributes = true;
+
 
 	WiretapConnector(ClientHttpConnector delegate) {
 		this.delegate = delegate;
@@ -84,6 +86,16 @@ class WiretapConnector implements ClientHttpConnector {
 				});
 	}
 
+	@Override
+	public void setApplyAttributes(boolean applyAttributes) {
+		this.applyAttributes = applyAttributes;
+	}
+
+	@Override
+	public boolean getApplyAttributes() {
+		return this.applyAttributes;
+	}
+
 	/**
 	 * Create the {@link ExchangeResult} for the given "request-id" header value.
 	 */

spring-test/src/main/java/org/springframework/test/web/servlet/client/MockMvcHttpConnector.java

@@ -86,6 +86,8 @@ public class MockMvcHttpConnector implements ClientHttpConnector {
 
 	private final List<RequestPostProcessor> requestPostProcessors;
 
+	private boolean applyAttributes = true;
+
 
 	public MockMvcHttpConnector(MockMvc mockMvc) {
 		this(mockMvc, Collections.emptyList());
@@ -115,6 +117,16 @@ public class MockMvcHttpConnector implements ClientHttpConnector {
 		}
 	}
 
+	@Override
+	public void setApplyAttributes(boolean applyAttributes) {
+		this.applyAttributes = applyAttributes;
+	}
+
+	@Override
+	public boolean getApplyAttributes() {
+		return this.applyAttributes;
+	}
+
 	private RequestBuilder adaptRequest(
 			HttpMethod httpMethod, URI uri, Function<? super ClientHttpRequest, Mono<Void>> requestCallback) {
 

spring-test/src/test/java/org/springframework/test/web/reactive/server/WiretapConnectorTests.java

@@ -18,6 +18,7 @@ package org.springframework.test.web.reactive.server;
 
 import java.net.URI;
 import java.time.Duration;
+import java.util.function.Function;
 
 import org.junit.jupiter.api.Test;
 import reactor.core.publisher.Mono;
@@ -48,7 +49,22 @@ public class WiretapConnectorTests {
 	public void captureAndClaim() {
 		ClientHttpRequest request = new MockClientHttpRequest(HttpMethod.GET, "/test");
 		ClientHttpResponse response = new MockClientHttpResponse(HttpStatus.OK);
-		ClientHttpConnector connector = (method, uri, fn) -> fn.apply(request).then(Mono.just(response));
+		ClientHttpConnector connector = new ClientHttpConnector() {
+			@Override
+			public Mono<ClientHttpResponse> connect(HttpMethod method, URI uri, Function<? super ClientHttpRequest, Mono<Void>> requestCallback) {
+				return requestCallback.apply(request).then(Mono.just(response));
+			}
+
+			@Override
+			public void setApplyAttributes(boolean applyAttributes) {
+
+			}
+
+			@Override
+			public boolean getApplyAttributes() {
+				return false;
+			}
+		};
 
 		ClientRequest clientRequest = ClientRequest.create(HttpMethod.GET, URI.create("/test"))
 				.header(WebTestClient.WEBTESTCLIENT_REQUEST_ID, "1").build();

spring-web/src/main/java/org/springframework/http/client/reactive/AbstractClientHttpRequest.java

@@ -17,7 +17,10 @@
 package org.springframework.http.client.reactive;
 
 import java.util.ArrayList;
+import java.util.Collections;
+import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Supplier;
 
@@ -55,6 +58,10 @@ public abstract class AbstractClientHttpRequest implements ClientHttpRequest {
 
 	private final MultiValueMap<String, HttpCookie> cookies;
 
+	private final Map<String, Object> attributes;
+
+	private final boolean applyAttributes;
+
 	private final AtomicReference<State> state = new AtomicReference<>(State.NEW);
 
 	private final List<Supplier<? extends Publisher<Void>>> commitActions = new ArrayList<>(4);
@@ -64,13 +71,19 @@ public abstract class AbstractClientHttpRequest implements ClientHttpRequest {
 
 
 	public AbstractClientHttpRequest() {
-		this(new HttpHeaders());
+		this(new HttpHeaders(), false);
+	}
+
+	public AbstractClientHttpRequest(boolean applyAttributes) {
+		this(new HttpHeaders(), applyAttributes);
 	}
 
-	public AbstractClientHttpRequest(HttpHeaders headers) {
+	public AbstractClientHttpRequest(HttpHeaders headers, boolean applyAttributes) {
 		Assert.notNull(headers, "HttpHeaders must not be null");
 		this.headers = headers;
 		this.cookies = new LinkedMultiValueMap<>();
+		this.attributes = new LinkedHashMap<>();
+		this.applyAttributes = applyAttributes;
 	}
 
 
@@ -106,6 +119,14 @@ public abstract class AbstractClientHttpRequest implements ClientHttpRequest {
 		return this.cookies;
 	}
 
+	@Override
+	public Map<String, Object> getAttributes() {
+		if (State.COMMITTED.equals(this.state.get())) {
+			return Collections.unmodifiableMap(this.attributes);
+		}
+		return this.attributes;
+	}
+
 	@Override
 	public void beforeCommit(Supplier<? extends Mono<Void>> action) {
 		Assert.notNull(action, "Action must not be null");
@@ -140,6 +161,9 @@ public abstract class AbstractClientHttpRequest implements ClientHttpRequest {
 				Mono.fromRunnable(() -> {
 					applyHeaders();
 					applyCookies();
+					if (this.applyAttributes) {
+						applyAttributes();
+					}
 					this.state.set(State.COMMITTED);
 				}));
 
@@ -168,4 +192,10 @@ public abstract class AbstractClientHttpRequest implements ClientHttpRequest {
 	 */
 	protected abstract void applyCookies();
 
+	/**
+	 * Add additional attributes from {@link #getAttributes()} to the underlying request.
+	 * This method is called once only.
+	 */
+	protected abstract void applyAttributes();
+
 }

spring-web/src/main/java/org/springframework/http/client/reactive/ClientHttpConnector.java

@@ -48,4 +48,14 @@ public interface ClientHttpConnector {
 	Mono<ClientHttpResponse> connect(HttpMethod method, URI uri,
 			Function<? super ClientHttpRequest, Mono<Void>> requestCallback);
 
+	/**
+	 * Set whether or not attributes should be applied to the underlying http-client library request.
+	 */
+	void setApplyAttributes(boolean applyAttributes);
+
+	/**
+	 * Whether or not attributes should be applied to the underlying http-client library request.
+	 */
+	boolean getApplyAttributes();
+
 }

spring-web/src/main/java/org/springframework/http/client/reactive/ClientHttpRequest.java

@@ -17,6 +17,7 @@
 package org.springframework.http.client.reactive;
 
 import java.net.URI;
+import java.util.Map;
 
 import org.springframework.http.HttpCookie;
 import org.springframework.http.HttpMethod;
@@ -54,4 +55,9 @@ public interface ClientHttpRequest extends ReactiveHttpOutputMessage {
 	 */
 	<T> T getNativeRequest();
 
+	/**
+	 * Return a mutable map of the request attributes.
+	 */
+	Map<String, Object> getAttributes();
+
 }

spring-web/src/main/java/org/springframework/http/client/reactive/ClientHttpRequestDecorator.java

@@ -17,6 +17,7 @@
 package org.springframework.http.client.reactive;
 
 import java.net.URI;
+import java.util.Map;
 import java.util.function.Supplier;
 
 import org.reactivestreams.Publisher;
@@ -85,6 +86,11 @@ public class ClientHttpRequestDecorator implements ClientHttpRequest {
 		return this.delegate.getNativeRequest();
 	}
 
+	@Override
+	public Map<String, Object> getAttributes() {
+		return this.delegate.getAttributes();
+	}
+
 	@Override
 	public void beforeCommit(Supplier<? extends Mono<Void>> action) {
 		this.delegate.beforeCommit(action);

spring-web/src/main/java/org/springframework/http/client/reactive/HttpComponentsClientHttpConnector.java

@@ -59,6 +59,7 @@ public class HttpComponentsClientHttpConnector implements ClientHttpConnector, C
 
 	private DataBufferFactory dataBufferFactory = DefaultDataBufferFactory.sharedInstance;
 
+	private boolean applyAttributes = true;
 
 	/**
 	 * Default constructor that creates and starts a new instance of {@link CloseableHttpAsyncClient}.
@@ -67,6 +68,7 @@ public class HttpComponentsClientHttpConnector implements ClientHttpConnector, C
 		this(HttpAsyncClients.createDefault());
 	}
 
+
 	/**
 	 * Constructor with a pre-configured {@link CloseableHttpAsyncClient} instance.
 	 * @param client the client to use
@@ -111,11 +113,22 @@ public class HttpComponentsClientHttpConnector implements ClientHttpConnector, C
 			context.setCookieStore(new BasicCookieStore());
 		}
 
-		HttpComponentsClientHttpRequest request =
-				new HttpComponentsClientHttpRequest(method, uri, context, this.dataBufferFactory);
+		HttpComponentsClientHttpRequest request = new HttpComponentsClientHttpRequest(
+				method, uri, context, this.dataBufferFactory, this.applyAttributes);
+
 		return requestCallback.apply(request).then(Mono.defer(() -> execute(request, context)));
 	}
 
+	@Override
+	public void setApplyAttributes(boolean applyAttributes) {
+		this.applyAttributes = applyAttributes;
+	}
+
+	@Override
+	public boolean getApplyAttributes() {
+		return this.applyAttributes;
+	}
+
 	private Mono<ClientHttpResponse> execute(HttpComponentsClientHttpRequest request, HttpClientContext context) {
 		AsyncRequestProducer requestProducer = request.toRequestProducer();
 

spring-web/src/main/java/org/springframework/http/client/reactive/HttpComponentsClientHttpRequest.java

@@ -66,8 +66,8 @@ class HttpComponentsClientHttpRequest extends AbstractClientHttpRequest {
 
 
 	public HttpComponentsClientHttpRequest(HttpMethod method, URI uri, HttpClientContext context,
-			DataBufferFactory dataBufferFactory) {
-
+			DataBufferFactory dataBufferFactory, boolean applyAttributes) {
+		super(applyAttributes);
 		this.context = context;
 		this.httpRequest = new BasicHttpRequest(method.name(), uri);
 		this.dataBufferFactory = dataBufferFactory;
@@ -157,6 +157,18 @@ class HttpComponentsClientHttpRequest extends AbstractClientHttpRequest {
 				});
 	}
 
+	/**
+	 * Applies the attributes to the {@link HttpClientContext}.
+	 */
+	@Override
+	protected void applyAttributes() {
+		getAttributes().forEach((key, value) -> {
+			if(this.context.getAttribute(key) == null) {
+				this.context.setAttribute(key, value);
+			}
+		});
+	}
+
 	@Override
 	protected HttpHeaders initReadOnlyHeaders() {
 		return HttpHeaders.readOnlyHttpHeaders(new HttpComponentsHeadersAdapter(this.httpRequest));

spring-web/src/main/java/org/springframework/http/client/reactive/JdkClientHttpConnector.java

@@ -96,7 +96,7 @@ public class JdkClientHttpConnector implements ClientHttpConnector {
 	public Mono<ClientHttpResponse> connect(
 			HttpMethod method, URI uri, Function<? super ClientHttpRequest, Mono<Void>> requestCallback) {
 
-		JdkClientHttpRequest jdkClientHttpRequest = new JdkClientHttpRequest(method, uri, this.bufferFactory);
+		JdkClientHttpRequest jdkClientHttpRequest = new JdkClientHttpRequest(method, uri, this.bufferFactory, getApplyAttributes());
 
 		return requestCallback.apply(jdkClientHttpRequest).then(Mono.defer(() -> {
 			HttpRequest httpRequest = jdkClientHttpRequest.getNativeRequest();
@@ -109,4 +109,19 @@ public class JdkClientHttpConnector implements ClientHttpConnector {
 		}));
 	}
 
+	/**
+	 * Sets nothing, since {@link JdkClientHttpConnector} does not offer any possibility to add attributes.
+	 */
+	@Override
+	public void setApplyAttributes(boolean applyAttributes) {
+	}
+
+	/**
+	 * Returns false, since {@link JdkClientHttpConnector} does not offer any possibility to add attributes.
+	 */
+	@Override
+	public boolean getApplyAttributes() {
+		return false;
+	}
+
 }

spring-web/src/main/java/org/springframework/http/client/reactive/JdkClientHttpRequest.java

@@ -56,7 +56,8 @@ class JdkClientHttpRequest extends AbstractClientHttpRequest {
 	private final HttpRequest.Builder builder;
 
 
-	public JdkClientHttpRequest(HttpMethod httpMethod, URI uri, DataBufferFactory bufferFactory) {
+	public JdkClientHttpRequest(HttpMethod httpMethod, URI uri, DataBufferFactory bufferFactory, boolean applyAttributes) {
+		super(applyAttributes);
 		Assert.notNull(httpMethod, "HttpMethod is required");
 		Assert.notNull(uri, "URI is required");
 		Assert.notNull(bufferFactory, "DataBufferFactory is required");
@@ -112,6 +113,15 @@ class JdkClientHttpRequest extends AbstractClientHttpRequest {
 				.flatMap(List::stream).map(HttpCookie::toString).collect(Collectors.joining(";")));
 	}
 
+	/**
+	 * Not implemented, since {@link HttpRequest} does not offer any possibility to add request attributes.
+	 */
+	@Override
+	protected void applyAttributes() {
+		// TODO
+		throw new RuntimeException(String.format("Using attributes is not available for %s", HttpRequest.class.getName()));
+	}
+
 	@Override
 	public Mono<Void> writeWith(Publisher<? extends DataBuffer> body) {
 		return doCommit(() -> {

spring-web/src/main/java/org/springframework/http/client/reactive/JettyClientHttpConnector.java

@@ -52,6 +52,8 @@ public class JettyClientHttpConnector implements ClientHttpConnector {
 
 	private DataBufferFactory bufferFactory = DefaultDataBufferFactory.sharedInstance;
 
+	private boolean applyAttributes = true;
+
 
 	/**
 	 * Default constructor that creates a new instance of {@link HttpClient}.
@@ -126,11 +128,21 @@ public class JettyClientHttpConnector implements ClientHttpConnector {
 		}
 
 		Request jettyRequest = this.httpClient.newRequest(uri).method(method.toString());
-		JettyClientHttpRequest request = new JettyClientHttpRequest(jettyRequest, this.bufferFactory);
+		JettyClientHttpRequest request = new JettyClientHttpRequest(jettyRequest, this.bufferFactory, getApplyAttributes());
 
 		return requestCallback.apply(request).then(execute(request));
 	}
 
+	@Override
+	public void setApplyAttributes(boolean applyAttributes) {
+		this.applyAttributes = applyAttributes;
+	}
+
+	@Override
+	public boolean getApplyAttributes() {
+		return this.applyAttributes;
+	}
+
 	private Mono<ClientHttpResponse> execute(JettyClientHttpRequest request) {
 		return Mono.fromDirect(request.toReactiveRequest()
 				.response((reactiveResponse, chunkPublisher) -> {

spring-web/src/main/java/org/springframework/http/client/reactive/JettyClientHttpRequest.java

@@ -55,7 +55,8 @@ class JettyClientHttpRequest extends AbstractClientHttpRequest {
 	private final ReactiveRequest.Builder builder;
 
 
-	public JettyClientHttpRequest(Request jettyRequest, DataBufferFactory bufferFactory) {
+	public JettyClientHttpRequest(Request jettyRequest, DataBufferFactory bufferFactory, boolean applyAttributes) {
+		super(applyAttributes);
 		this.jettyRequest = jettyRequest;
 		this.bufferFactory = bufferFactory;
 		this.builder = ReactiveRequest.newBuilder(this.jettyRequest).abortOnCancel(true);
@@ -138,6 +139,14 @@ class JettyClientHttpRequest extends AbstractClientHttpRequest {
 				.forEach(this.jettyRequest::cookie);
 	}
 
+	/**
+	 * Applies the attributes to {@link Request#getAttributes()}.
+	 */
+	@Override
+	protected void applyAttributes() {
+		getAttributes().forEach(this.jettyRequest::attribute);
+	}
+
 	@Override
 	protected void applyHeaders() {
 		HttpHeaders headers = getHeaders();

spring-web/src/main/java/org/springframework/http/client/reactive/ReactorClientHttpConnector.java

@@ -66,6 +66,7 @@ public class ReactorClientHttpConnector implements ClientHttpConnector, SmartLif
 
 	private final Object lifecycleMonitor = new Object();
 
+	private boolean applyAttributes = true;
 
 	/**
 	 * Default constructor. Initializes {@link HttpClient} via:
@@ -170,10 +171,20 @@ public class ReactorClientHttpConnector implements ClientHttpConnector, SmartLif
 		return requestSender.uri(uri.toString());
 	}
 
+	@Override
+	public void setApplyAttributes(boolean applyAttributes) {
+		this.applyAttributes = applyAttributes;
+	}
+
+	@Override
+	public boolean getApplyAttributes() {
+		return this.applyAttributes;
+	}
+
 	private ReactorClientHttpRequest adaptRequest(HttpMethod method, URI uri, HttpClientRequest request,
 			NettyOutbound nettyOutbound) {
 
-		return new ReactorClientHttpRequest(method, uri, request, nettyOutbound);
+		return new ReactorClientHttpRequest(method, uri, request, nettyOutbound, this.applyAttributes);
 	}
 
 	@Override

spring-web/src/main/java/org/springframework/http/client/reactive/ReactorClientHttpRequest.java

@@ -18,13 +18,16 @@ package org.springframework.http.client.reactive;
 
 import java.net.URI;
 import java.nio.file.Path;
+import java.util.Map;
 
 import io.netty.buffer.ByteBuf;
 import io.netty.handler.codec.http.cookie.DefaultCookie;
+import io.netty.util.AttributeKey;
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 import reactor.netty.NettyOutbound;
+import reactor.netty.channel.ChannelOperations;
 import reactor.netty.http.client.HttpClientRequest;
 
 import org.springframework.core.io.buffer.DataBuffer;
@@ -45,6 +48,8 @@ import org.springframework.http.support.Netty4HeadersAdapter;
  */
 class ReactorClientHttpRequest extends AbstractClientHttpRequest implements ZeroCopyHttpOutputMessage {
 
+	public static final String ATTRIBUTES_CHANNEL_KEY = "attributes";
+
 	private final HttpMethod httpMethod;
 
 	private final URI uri;
@@ -56,7 +61,8 @@ class ReactorClientHttpRequest extends AbstractClientHttpRequest implements Zero
 	private final NettyDataBufferFactory bufferFactory;
 
 
-	public ReactorClientHttpRequest(HttpMethod method, URI uri, HttpClientRequest request, NettyOutbound outbound) {
+	public ReactorClientHttpRequest(HttpMethod method, URI uri, HttpClientRequest request, NettyOutbound outbound, boolean applyAttributes) {
+		super(applyAttributes);
 		this.httpMethod = method;
 		this.uri = uri;
 		this.request = request;
@@ -135,6 +141,17 @@ class ReactorClientHttpRequest extends AbstractClientHttpRequest implements Zero
 		}));
 	}
 
+	/**
+	 * Applies the request attributes to the {@link reactor.netty.http.client.HttpClientRequest} by setting
+	 * a single {@link Map} into the {@link reactor.netty.channel.ChannelOperations#channel()},
+	 * with {@link io.netty5.util.AttributeKey#name()} equal to {@link #ATTRIBUTES_CHANNEL_KEY}.
+	 */
+	@Override
+	protected void applyAttributes() {
+		((ChannelOperations<?, ?>) this.request)
+				.channel().attr(AttributeKey.valueOf(ATTRIBUTES_CHANNEL_KEY)).set(getAttributes());
+	}
+
 	@Override
 	protected HttpHeaders initReadOnlyHeaders() {
 		return HttpHeaders.readOnlyHttpHeaders(new Netty4HeadersAdapter(this.request.requestHeaders()));

spring-web/src/main/java/org/springframework/http/client/reactive/ReactorNetty2ClientHttpConnector.java

@@ -46,6 +46,8 @@ public class ReactorNetty2ClientHttpConnector implements ClientHttpConnector {
 
 	private final HttpClient httpClient;
 
+	private boolean applyAttributes = true;
+
 
 	/**
 	 * Default constructor. Initializes {@link HttpClient} via:
@@ -126,10 +128,20 @@ public class ReactorNetty2ClientHttpConnector implements ClientHttpConnector {
 				});
 	}
 
+	@Override
+	public void setApplyAttributes(boolean applyAttributes) {
+		this.applyAttributes = applyAttributes;
+	}
+
+	@Override
+	public boolean getApplyAttributes() {
+		return this.applyAttributes;
+	}
+
 	private ReactorNetty2ClientHttpRequest adaptRequest(HttpMethod method, URI uri, HttpClientRequest request,
 			NettyOutbound nettyOutbound) {
 
-		return new ReactorNetty2ClientHttpRequest(method, uri, request, nettyOutbound);
+		return new ReactorNetty2ClientHttpRequest(method, uri, request, nettyOutbound, getApplyAttributes());
 	}
 
 }

spring-web/src/main/java/org/springframework/http/client/reactive/ReactorNetty2ClientHttpRequest.java

@@ -18,13 +18,16 @@ package org.springframework.http.client.reactive;
 
 import java.net.URI;
 import java.nio.file.Path;
+import java.util.Map;
 
 import io.netty5.buffer.Buffer;
 import io.netty5.handler.codec.http.headers.DefaultHttpCookiePair;
+import io.netty5.util.AttributeKey;
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 import reactor.netty5.NettyOutbound;
+import reactor.netty5.channel.ChannelOperations;
 import reactor.netty5.http.client.HttpClientRequest;
 
 import org.springframework.core.io.buffer.DataBuffer;
@@ -46,6 +49,8 @@ import org.springframework.http.support.Netty5HeadersAdapter;
  */
 class ReactorNetty2ClientHttpRequest extends AbstractClientHttpRequest implements ZeroCopyHttpOutputMessage {
 
+	public static final String ATTRIBUTES_CHANNEL_KEY = "attributes";
+
 	private final HttpMethod httpMethod;
 
 	private final URI uri;
@@ -57,7 +62,8 @@ class ReactorNetty2ClientHttpRequest extends AbstractClientHttpRequest implement
 	private final Netty5DataBufferFactory bufferFactory;
 
 
-	public ReactorNetty2ClientHttpRequest(HttpMethod method, URI uri, HttpClientRequest request, NettyOutbound outbound) {
+	public ReactorNetty2ClientHttpRequest(HttpMethod method, URI uri, HttpClientRequest request, NettyOutbound outbound, boolean applyAttributes) {
+		super(applyAttributes);
 		this.httpMethod = method;
 		this.uri = uri;
 		this.request = request;
@@ -136,6 +142,17 @@ class ReactorNetty2ClientHttpRequest extends AbstractClientHttpRequest implement
 		}));
 	}
 
+	/**
+	 * Applies the request attributes to the {@link reactor.netty.http.client.HttpClientRequest} by setting
+	 * a single {@link Map} into the {@link reactor.netty.channel.ChannelOperations#channel()},
+	 * with {@link AttributeKey#name()} equal to {@link #ATTRIBUTES_CHANNEL_KEY}.
+	 */
+	@Override
+	protected void applyAttributes() {
+		((ChannelOperations<?, ?>) this.request)
+				.channel().attr(AttributeKey.valueOf(ATTRIBUTES_CHANNEL_KEY)).set(getAttributes());
+	}
+
 	@Override
 	protected HttpHeaders initReadOnlyHeaders() {
 		return HttpHeaders.readOnlyHttpHeaders(new Netty5HeadersAdapter(this.request.requestHeaders()));

spring-web/src/testFixtures/java/org/springframework/web/testfixture/http/client/reactive/MockClientHttpRequest.java

@@ -121,6 +121,10 @@ public class MockClientHttpRequest extends AbstractClientHttpRequest implements
 				.forEach(cookie -> getHeaders().add(HttpHeaders.COOKIE, cookie.toString()));
 	}
 
+	@Override
+	protected void applyAttributes() {
+	}
+
 	@Override
 	public Mono<Void> writeWith(Publisher<? extends DataBuffer> body) {
 		return doCommit(() -> Mono.defer(() -> this.writeHandler.apply(Flux.from(body))));

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

@@ -265,6 +265,12 @@ final class DefaultClientRequestBuilder implements ClientRequest.Builder {
 					requestCookies.add(name, cookie);
 				}));
 			}
+
+			Map<String, Object> requestAttributes = request.getAttributes();
+			if (!this.attributes.isEmpty()) {
+				this.attributes.forEach((key, value) -> requestAttributes.put(key, value));
+			}
+
 			if (this.httpRequestConsumer != null) {
 				this.httpRequestConsumer.accept(request);
 			}

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

@@ -89,6 +89,8 @@ final class DefaultWebClientBuilder implements WebClient.Builder {
 	@Nullable
 	private MultiValueMap<String, String> defaultCookies;
 
+	private boolean applyAttributes;
+
 	@Nullable
 	private Consumer<WebClient.RequestHeadersSpec<?>> defaultRequest;
 
@@ -137,6 +139,7 @@ final class DefaultWebClientBuilder implements WebClient.Builder {
 
 		this.defaultCookies = (other.defaultCookies != null ?
 				new LinkedMultiValueMap<>(other.defaultCookies) : null);
+		this.applyAttributes = other.applyAttributes;
 		this.defaultRequest = other.defaultRequest;
 		this.statusHandlers = (other.statusHandlers != null ? new LinkedHashMap<>(other.statusHandlers) : null);
 		this.filters = (other.filters != null ? new ArrayList<>(other.filters) : null);
@@ -200,6 +203,12 @@ final class DefaultWebClientBuilder implements WebClient.Builder {
 		return this;
 	}
 
+	@Override
+	public WebClient.Builder applyAttributes(boolean applyAttributes) {
+		this.applyAttributes = applyAttributes;
+		return this;
+	}
+
 	private MultiValueMap<String, String> initCookies() {
 		if (this.defaultCookies == null) {
 			this.defaultCookies = new LinkedMultiValueMap<>(3);
@@ -335,21 +344,24 @@ final class DefaultWebClientBuilder implements WebClient.Builder {
 	}
 
 	private ClientHttpConnector initConnector() {
+		final ClientHttpConnector connector;
 		if (reactorNettyClientPresent) {
-			return new ReactorClientHttpConnector();
+			connector = new ReactorClientHttpConnector();
 		}
 		else if (reactorNetty2ClientPresent) {
 			return new ReactorNetty2ClientHttpConnector();
 		}
 		else if (jettyClientPresent) {
-			return new JettyClientHttpConnector();
+			connector = new JettyClientHttpConnector();
 		}
 		else if (httpComponentsClientPresent) {
-			return new HttpComponentsClientHttpConnector();
+			connector = new HttpComponentsClientHttpConnector();
 		}
 		else {
-			return new JdkClientHttpConnector();
+			connector = new JdkClientHttpConnector();
 		}
+		connector.setApplyAttributes(this.applyAttributes);
+		return connector;
 	}
 
 	private ExchangeStrategies initExchangeStrategies() {

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

@@ -250,6 +250,13 @@ public interface WebClient {
 		 */
 		Builder defaultCookies(Consumer<MultiValueMap<String, String>> cookiesConsumer);
 
+		/**
+		 * Global option to specify whether or not the request attributes should be applied
+		 * to the underlying http-client request, if the used {@link ClientHttpConnector} allows it.
+		 * @param applyAttributes whether or not to apply the attributes
+		 */
+		Builder applyAttributes(boolean applyAttributes);
+
 		/**
 		 * Provide a consumer to customize every request being built.
 		 * @param defaultRequest the consumer to use for modifying requests

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

@@ -34,14 +34,18 @@ import java.time.Duration;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Consumer;
 import java.util.function.Function;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
+import io.netty.util.Attribute;
+import io.netty.util.AttributeKey;
 import okhttp3.mockwebserver.MockResponse;
 import okhttp3.mockwebserver.MockWebServer;
 import okhttp3.mockwebserver.RecordedRequest;
+import org.eclipse.jetty.client.Request;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Named;
 import org.junit.jupiter.api.Test;
@@ -50,6 +54,7 @@ import org.junit.jupiter.params.provider.MethodSource;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 import reactor.core.publisher.Sinks;
+import reactor.netty.channel.ChannelOperations;
 import reactor.netty.http.client.HttpClient;
 import reactor.netty.resources.ConnectionProvider;
 import reactor.test.StepVerifier;
@@ -186,6 +191,67 @@ class WebClientIntegrationTests {
 		});
 	}
 
+	@ParameterizedWebClientTest
+	void applyAttributesInNativeRequest(ClientHttpConnector connector) {
+		startServer(connector);
+		connector.setApplyAttributes(true);
+		checkAttributesInNativeRequest(true);
+	}
+
+	@ParameterizedWebClientTest
+	void dontApplyAttributesInNativeRequest(ClientHttpConnector connector) {
+		startServer(connector);
+		connector.setApplyAttributes(false);
+		checkAttributesInNativeRequest(false);
+	}
+
+	private void checkAttributesInNativeRequest(boolean expectAttributesApplied){
+		prepareResponse(response -> {});
+
+		final AtomicReference<Object> nativeRequest = new AtomicReference<>();
+		Mono<Void> result = this.webClient.get()
+				.uri("/pojo")
+				.attribute("foo","bar")
+				.httpRequest(clientHttpRequest -> nativeRequest.set(clientHttpRequest.getNativeRequest()))
+				.retrieve()
+				.bodyToMono(Void.class);
+		StepVerifier.create(result)
+				.expectComplete()
+				.verify();
+		if (nativeRequest.get() instanceof ChannelOperations<?,?> nativeReq) {
+			Attribute<Map<String, Object>> attributes = nativeReq.channel().attr(AttributeKey.valueOf("attributes"));
+			if (expectAttributesApplied) {
+				assertThat(attributes.get()).isNotNull();
+				assertThat(attributes.get()).containsEntry("foo", "bar");
+			}
+			else {
+				assertThat(attributes.get()).isNull();
+			}
+		}
+		else if (nativeRequest.get() instanceof reactor.netty5.channel.ChannelOperations<?,?> nativeReq) {
+			io.netty5.util.Attribute<Map<String, Object>> attributes = nativeReq.channel().attr(io.netty5.util.AttributeKey.valueOf("attributes"));
+			if (expectAttributesApplied) {
+				assertThat(attributes.get()).isNotNull();
+				assertThat(attributes.get()).containsEntry("foo", "bar");
+			}
+			else {
+				assertThat(attributes.get()).isNull();
+			}
+		}
+		else if (nativeRequest.get() instanceof Request nativeReq) {
+			if (expectAttributesApplied) {
+				assertThat(nativeReq.getAttributes()).containsEntry("foo", "bar");
+			}
+			else {
+				assertThat(nativeReq.getAttributes()).doesNotContainEntry("foo", "bar");
+			}
+		}
+		else if (nativeRequest.get() instanceof org.apache.hc.core5.http.HttpRequest nativeReq) {
+			// TODO get attributes from HttpClientContext
+		}
+	}
+
+
 	@ParameterizedWebClientTest
 	void retrieveJsonWithParameterizedTypeReference(ClientHttpConnector connector) {
 		startServer(connector);