Introduce request attributes in RestClient

This commit introduces request attributes in the RestClient and
underlying infrastructure (i.e. HttpRequest).

Closes gh-32027

framework-docs/modules/ROOT/pages/integration/rest-clients.adoc

@@ -1007,7 +1007,8 @@ method parameters:
   is supported for non-String values.
 
 | `@RequestAttribute`
-| Provide an `Object` to add as a request attribute. Only supported by `WebClient`.
+| Provide an `Object` to add as a request attribute. Only supported by `RestClient`
+  and `WebClient`.
 
 | `@RequestBody`
 | Provide the body of the request either as an Object to be serialized, or a

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

@@ -18,6 +18,8 @@
 
 import java.io.IOException;
 import java.net.URI;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 
 import org.springframework.http.HttpMethod;
 import org.springframework.http.client.ClientHttpRequest;
@@ -46,6 +48,9 @@ public class MockClientHttpRequest extends MockHttpOutputMessage implements Clie
 
 	private boolean executed = false;
 
+	@Nullable
+	Map<String, Object> attributes;
+
 
 	/**
 	 * Create a {@code MockClientHttpRequest} with {@link HttpMethod#GET GET} as
@@ -115,6 +120,16 @@ public boolean isExecuted() {
 		return this.executed;
 	}
 
+	@Override
+	public Map<String, Object> getAttributes() {
+		Map<String, Object> attributes = this.attributes;
+		if (attributes == null) {
+			attributes = new ConcurrentHashMap<>();
+			this.attributes = attributes;
+		}
+		return attributes;
+	}
+
 	/**
 	 * Set the {@link #isExecuted() executed} flag to {@code true} and return the
 	 * configured {@link #setResponse(ClientHttpResponse) response}.

spring-web/src/main/java/org/springframework/http/HttpRequest.java

@@ -17,6 +17,7 @@
 package org.springframework.http;
 
 import java.net.URI;
+import java.util.Map;
 
 /**
  * Represents an HTTP request message, consisting of a
@@ -41,4 +42,10 @@ public interface HttpRequest extends HttpMessage {
 	 */
 	URI getURI();
 
+	/**
+	 * Return a mutable map of request attributes for this request.
+	 * @since 6.2
+	 */
+	Map<String, Object> getAttributes();
+
 }

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

@@ -18,6 +18,8 @@
 
 import java.io.IOException;
 import java.io.OutputStream;
+import java.util.LinkedHashMap;
+import java.util.Map;
 
 import org.springframework.http.HttpHeaders;
 import org.springframework.lang.Nullable;
@@ -39,6 +41,9 @@ public abstract class AbstractClientHttpRequest implements ClientHttpRequest {
 	@Nullable
 	private HttpHeaders readOnlyHeaders;
 
+	@Nullable
+	private Map<String, Object> attributes;
+
 
 	@Override
 	public final HttpHeaders getHeaders() {
@@ -60,6 +65,16 @@ public final OutputStream getBody() throws IOException {
 		return getBodyInternal(this.headers);
 	}
 
+	@Override
+	public Map<String, Object> getAttributes() {
+		Map<String, Object> attributes = this.attributes;
+		if (attributes == null) {
+			attributes = new LinkedHashMap<>();
+			this.attributes = attributes;
+		}
+		return attributes;
+	}
+
 	@Override
 	public final ClientHttpResponse execute() throws IOException {
 		assertNotExecuted();

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

@@ -91,6 +91,7 @@ public ClientHttpResponse execute(HttpRequest request, byte[] body) throws IOExc
 				HttpMethod method = request.getMethod();
 				ClientHttpRequest delegate = requestFactory.createRequest(request.getURI(), method);
 				request.getHeaders().forEach((key, value) -> delegate.getHeaders().addAll(key, value));
+				request.getAttributes().forEach((key, value) -> delegate.getAttributes().put(key, value));
 				if (body.length > 0) {
 					if (delegate instanceof StreamingHttpOutputMessage streamingOutputMessage) {
 						streamingOutputMessage.setBody(new StreamingHttpOutputMessage.Body() {

spring-web/src/main/java/org/springframework/http/client/support/HttpRequestWrapper.java

@@ -17,6 +17,7 @@
 package org.springframework.http.client.support;
 
 import java.net.URI;
+import java.util.Map;
 
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
@@ -70,6 +71,14 @@ public URI getURI() {
 		return this.request.getURI();
 	}
 
+	/**
+	 * Return the attributes of the wrapped request.
+	 */
+	@Override
+	public Map<String, Object> getAttributes() {
+		return this.request.getAttributes();
+	}
+
 	/**
 	 * Return the headers of the wrapped request.
 	 */

spring-web/src/main/java/org/springframework/http/server/ServletServerHttpRequest.java

@@ -29,11 +29,16 @@
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
 import java.security.Principal;
+import java.util.AbstractCollection;
+import java.util.AbstractMap;
+import java.util.AbstractSet;
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.Enumeration;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 import jakarta.servlet.http.HttpServletRequest;
 
@@ -67,6 +72,10 @@ public class ServletServerHttpRequest implements ServerHttpRequest {
 	@Nullable
 	private HttpHeaders headers;
 
+	@Nullable
+	private Map<String, Object> attributes;
+
+
 	@Nullable
 	private ServerHttpAsyncRequestControl asyncRequestControl;
 
@@ -207,6 +216,16 @@ public InetSocketAddress getRemoteAddress() {
 		return new InetSocketAddress(this.servletRequest.getRemoteHost(), this.servletRequest.getRemotePort());
 	}
 
+	@Override
+	public Map<String, Object> getAttributes() {
+		Map<String, Object> attributes = this.attributes;
+		if (attributes == null) {
+			attributes = new AttributesMap();
+			this.attributes = attributes;
+		}
+		return attributes;
+	}
+
 	@Override
 	public InputStream getBody() throws IOException {
 		if (isFormPost(this.servletRequest) && this.servletRequest.getQueryString() == null) {
@@ -276,4 +295,151 @@ private InputStream getBodyFromServletRequestParameters(HttpServletRequest reque
 		return new ByteArrayInputStream(bytes);
 	}
 
+
+	private final class AttributesMap extends AbstractMap<String, Object> {
+
+		@Nullable
+		private transient Set<String> keySet;
+
+		@Nullable
+		private transient Collection<Object> values;
+
+		@Nullable
+		private transient Set<Entry<String, Object>> entrySet;
+
+
+		@Override
+		public int size() {
+			int size = 0;
+			for (Enumeration<?> names = servletRequest.getAttributeNames(); names.hasMoreElements(); names.nextElement()) {
+				size++;
+			}
+			return size;
+		}
+
+		@Override
+		@Nullable
+		public Object get(Object key) {
+			if (key instanceof String name) {
+				return servletRequest.getAttribute(name);
+			}
+			else {
+				return null;
+			}
+		}
+
+		@Override
+		@Nullable
+		public Object put(String key, Object value) {
+			Object old = get(key);
+			servletRequest.setAttribute(key, value);
+			return old;
+		}
+
+		@Override
+		@Nullable
+		public Object remove(Object key) {
+			if (key instanceof String name) {
+				Object old = get(key);
+				servletRequest.removeAttribute(name);
+				return old;
+			}
+			else {
+				return null;
+			}
+		}
+
+		@Override
+		public void clear() {
+			for (Enumeration<String> names = servletRequest.getAttributeNames(); names.hasMoreElements(); ) {
+				String name = names.nextElement();
+				servletRequest.removeAttribute(name);
+			}
+		}
+
+		@Override
+		public Set<String> keySet() {
+			Set<String> keySet = this.keySet;
+			if (keySet == null) {
+				keySet = new AbstractSet<>() {
+					@Override
+					public Iterator<String> iterator() {
+						return servletRequest.getAttributeNames().asIterator();
+					}
+
+					@Override
+					public int size() {
+						return AttributesMap.this.size();
+					}
+				};
+				this.keySet = keySet;
+			}
+			return keySet;
+		}
+
+		@Override
+		public Collection<Object> values() {
+			Collection<Object> values = this.values;
+			if (values == null) {
+				values = new AbstractCollection<>() {
+					@Override
+					public Iterator<Object> iterator() {
+						Enumeration<String> e = servletRequest.getAttributeNames();
+						return new Iterator<>() {
+							@Override
+							public boolean hasNext() {
+								return e.hasMoreElements();
+							}
+
+							@Override
+							public Object next() {
+								String name = e.nextElement();
+								return servletRequest.getAttribute(name);
+							}
+						};
+					}
+
+					@Override
+					public int size() {
+						return AttributesMap.this.size();
+					}
+				};
+				this.values = values;
+			}
+			return values;
+		}
+
+		@Override
+		public Set<Entry<String, Object>> entrySet() {
+			Set<Entry<String, Object>> entrySet = this.entrySet;
+			if (entrySet == null) {
+				entrySet = new AbstractSet<>() {
+					@Override
+					public Iterator<Entry<String, Object>> iterator() {
+						Enumeration<String> e = servletRequest.getAttributeNames();
+						return new Iterator<>() {
+							@Override
+							public boolean hasNext() {
+								return e.hasMoreElements();
+							}
+
+							@Override
+							public Entry<String, Object> next() {
+								String name = e.nextElement();
+								Object value = servletRequest.getAttribute(name);
+								return new SimpleImmutableEntry<>(name, value);
+							}
+						};
+					}
+
+					@Override
+					public int size() {
+						return AttributesMap.this.size();
+					}
+				};
+				this.entrySet = entrySet;
+			}
+			return entrySet;
+		}
+	}
 }

spring-web/src/main/java/org/springframework/http/server/reactive/AbstractServerHttpRequest.java

@@ -19,6 +19,9 @@
 import java.net.URI;
 import java.net.URLDecoder;
 import java.nio.charset.StandardCharsets;
+import java.util.Collections;
+import java.util.Map;
+import java.util.function.Supplier;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -68,6 +71,9 @@ public abstract class AbstractServerHttpRequest implements ServerHttpRequest {
 	@Nullable
 	private String logPrefix;
 
+	@Nullable
+	private Supplier<Map<String, Object>> attributesSupplier;
+
 
 	/**
 	 * Constructor with the method, URI and headers for the request.
@@ -122,6 +128,16 @@ public URI getURI() {
 		return this.uri;
 	}
 
+	@Override
+	public Map<String, Object> getAttributes() {
+		if (this.attributesSupplier != null) {
+			return this.attributesSupplier.get();
+		}
+		else {
+			return Collections.emptyMap();
+		}
+	}
+
 	@Override
 	public RequestPath getPath() {
 		return this.path;
@@ -230,4 +246,12 @@ protected String initLogPrefix() {
 		return getId();
 	}
 
+	/**
+	 * Set the attribute supplier.
+	 * <p><strong>Note:</strong> This is exposed mainly for internal framework
+	 * use.
+	 */
+	public void setAttributesSupplier(Supplier<Map<String, Object>> attributesSupplier) {
+		this.attributesSupplier = attributesSupplier;
+	}
 }

spring-web/src/main/java/org/springframework/http/server/reactive/ServerHttpRequestDecorator.java

@@ -18,6 +18,7 @@
 
 import java.net.InetSocketAddress;
 import java.net.URI;
+import java.util.Map;
 
 import reactor.core.publisher.Flux;
 
@@ -70,6 +71,11 @@ public URI getURI() {
 		return getDelegate().getURI();
 	}
 
+	@Override
+	public Map<String, Object> getAttributes() {
+		return getDelegate().getAttributes();
+	}
+
 	@Override
 	public RequestPath getPath() {
 		return getDelegate().getPath();