Allow custom observation convention for RestClient

This commit allows to use a custom `ObservationConvention`
in the `DefaultRestClient`, and to set it through the
`RestClient.Builder`.

Closes gh-31325

spring-web/src/main/java/org/springframework/web/client/DefaultRestClient.java

@@ -107,6 +107,9 @@ final class DefaultRestClient implements RestClient {
 
 	private final ObservationRegistry observationRegistry;
 
+	@Nullable
+	private final ClientRequestObservationConvention observationConvention;
+
 
 	DefaultRestClient(ClientHttpRequestFactory clientRequestFactory,
 			@Nullable List<ClientHttpRequestInterceptor> interceptors,
@@ -116,6 +119,7 @@ final class DefaultRestClient implements RestClient {
 			@Nullable List<StatusHandler> statusHandlers,
 			List<HttpMessageConverter<?>> messageConverters,
 			ObservationRegistry observationRegistry,
+			@Nullable ClientRequestObservationConvention observationConvention,
 			DefaultRestClientBuilder builder) {
 
 		this.clientRequestFactory = clientRequestFactory;
@@ -126,6 +130,7 @@ final class DefaultRestClient implements RestClient {
 		this.defaultStatusHandlers = (statusHandlers != null ? new ArrayList<>(statusHandlers) : new ArrayList<>());
 		this.messageConverters = messageConverters;
 		this.observationRegistry = observationRegistry;
+		this.observationConvention = observationConvention;
 		this.builder = builder;
 	}
 
@@ -393,7 +398,7 @@ final class DefaultRestClient implements RestClient {
 				clientRequest.getHeaders().addAll(headers);
 				ClientRequestObservationContext observationContext = new ClientRequestObservationContext(clientRequest);
 				observationContext.setUriTemplate((String) this.attributes.get(URI_TEMPLATE_ATTRIBUTE));
-				observation = ClientHttpObservationDocumentation.HTTP_CLIENT_EXCHANGES.observation(null,
+				observation = ClientHttpObservationDocumentation.HTTP_CLIENT_EXCHANGES.observation(observationConvention,
 						DEFAULT_OBSERVATION_CONVENTION, () -> observationContext, observationRegistry).start();
 				if (this.body != null) {
 					this.body.writeTo(clientRequest);

spring-web/src/main/java/org/springframework/web/client/DefaultRestClientBuilder.java

@@ -35,6 +35,7 @@ import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
 import org.springframework.http.client.JdkClientHttpRequestFactory;
 import org.springframework.http.client.JettyClientHttpRequestFactory;
 import org.springframework.http.client.SimpleClientHttpRequestFactory;
+import org.springframework.http.client.observation.ClientRequestObservationConvention;
 import org.springframework.http.converter.ByteArrayHttpMessageConverter;
 import org.springframework.http.converter.HttpMessageConverter;
 import org.springframework.http.converter.ResourceHttpMessageConverter;
@@ -132,6 +133,9 @@ final class DefaultRestClientBuilder implements RestClient.Builder {
 
 	private ObservationRegistry observationRegistry = ObservationRegistry.NOOP;
 
+	@Nullable
+	private ClientRequestObservationConvention observationConvention;
+
 
 	public DefaultRestClientBuilder() {
 	}
@@ -161,6 +165,7 @@ final class DefaultRestClientBuilder implements RestClient.Builder {
 		this.interceptors = (other.interceptors != null) ? new ArrayList<>(other.interceptors) : null;
 		this.initializers = (other.initializers != null) ? new ArrayList<>(other.initializers) : null;
 		this.observationRegistry = other.observationRegistry;
+		this.observationConvention = other.observationConvention;
 	}
 
 	public DefaultRestClientBuilder(RestTemplate restTemplate) {
@@ -182,6 +187,7 @@ final class DefaultRestClientBuilder implements RestClient.Builder {
 			this.initializers = new ArrayList<>(restTemplate.getClientHttpRequestInitializers());
 		}
 		this.observationRegistry = restTemplate.getObservationRegistry();
+		this.observationConvention = restTemplate.getObservationConvention();
 	}
 
 
@@ -307,6 +313,12 @@ final class DefaultRestClientBuilder implements RestClient.Builder {
 		return this;
 	}
 
+	@Override
+	public RestClient.Builder observationConvention(ClientRequestObservationConvention observationConvention) {
+		this.observationConvention = observationConvention;
+		return this;
+	}
+
 	@Override
 	public RestClient.Builder apply(Consumer<RestClient.Builder> builderConsumer) {
 		builderConsumer.accept(this);
@@ -362,6 +374,7 @@ final class DefaultRestClientBuilder implements RestClient.Builder {
 				this.statusHandlers,
 				messageConverters,
 				this.observationRegistry,
+				this.observationConvention,
 				new DefaultRestClientBuilder(this)
 				);
 	}

spring-web/src/main/java/org/springframework/web/client/RestClient.java

@@ -42,6 +42,7 @@ import org.springframework.http.client.ClientHttpRequestFactory;
 import org.springframework.http.client.ClientHttpRequestInitializer;
 import org.springframework.http.client.ClientHttpRequestInterceptor;
 import org.springframework.http.client.ClientHttpResponse;
+import org.springframework.http.client.observation.ClientRequestObservationConvention;
 import org.springframework.http.converter.HttpMessageConverter;
 import org.springframework.lang.Nullable;
 import org.springframework.web.util.DefaultUriBuilderFactory;
@@ -374,6 +375,16 @@ public interface RestClient {
 		 */
 		Builder observationRegistry(ObservationRegistry observationRegistry);
 
+		/**
+		 * Configure the {@link io.micrometer.observation.ObservationConvention} to use
+		 * for collecting metadata for the request observation. Will use
+		 * {@link org.springframework.http.client.observation.DefaultClientRequestObservationConvention}
+		 * if none provided.
+		 * @param observationConvention the observation convention to use
+		 * @return this builder
+		 */
+		Builder observationConvention(ClientRequestObservationConvention observationConvention);
+
 		/**
 		 * Apply the given {@code Consumer} to this builder instance.
 		 * <p>This can be useful for applying pre-packaged customizations.

spring-web/src/main/java/org/springframework/web/client/RestTemplate.java

@@ -375,6 +375,15 @@ public class RestTemplate extends InterceptingHttpAccessor implements RestOperat
 		this.observationConvention = observationConvention;
 	}
 
+	/**
+	 * Return the configured {@link ClientRequestObservationConvention}, or {@code null} if not set.
+	 * @since 6.1
+	 */
+	@Nullable
+	public ClientRequestObservationConvention getObservationConvention() {
+		return this.observationConvention;
+	}
+
 	// GET
 
 	@Override