Creates HttpClientCustomizer.

This allows users to customize the Reactor Netty HttpClient without loosing auto configuration.

fixes gh-1546

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/config/GatewayAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2019 the original author or authors.
+ * Copyright 2013-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -137,9 +137,11 @@ import org.springframework.context.annotation.Conditional;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.DependsOn;
 import org.springframework.context.annotation.Primary;
+import org.springframework.core.annotation.AnnotationAwareOrderComparator;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.env.Environment;
 import org.springframework.http.codec.ServerCodecConfigurer;
+import org.springframework.util.CollectionUtils;
 import org.springframework.util.StringUtils;
 import org.springframework.validation.Validator;
 import org.springframework.web.reactive.DispatcherHandler;
@@ -579,7 +581,8 @@ public class GatewayAutoConfiguration {
 
 		@Bean
 		@ConditionalOnMissingBean
-		public HttpClient gatewayHttpClient(HttpClientProperties properties) {
+		public HttpClient gatewayHttpClient(HttpClientProperties properties,
+				List<HttpClientCustomizer> customizers) {
 
 			// configure pool resources
 			HttpClientProperties.Pool pool = properties.getPool();
@@ -599,6 +602,7 @@ public class GatewayAutoConfiguration {
 			}
 
 			HttpClient httpClient = HttpClient.create(connectionProvider)
+					// TODO: move customizations to HttpClientCustomizers
 					.httpResponseDecoder(spec -> {
 						if (properties.getMaxHeaderSize() != null) {
 							// cast to int is ok, since @Max is Integer.MAX_VALUE
@@ -677,6 +681,13 @@ public class GatewayAutoConfiguration {
 				httpClient = httpClient.wiretap(true);
 			}
 
+			if (!CollectionUtils.isEmpty(customizers)) {
+				customizers.sort(AnnotationAwareOrderComparator.INSTANCE);
+				for (HttpClientCustomizer customizer : customizers) {
+					httpClient = customizer.customize(httpClient);
+				}
+			}
+
 			return httpClient;
 		}
 

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/config/HttpClientCustomizer.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2013-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.gateway.config;
+
+import reactor.netty.http.client.HttpClient;
+
+@FunctionalInterface
+public interface HttpClientCustomizer {
+
+	/**
+	 * Customize the specified {@link HttpClient}.
+	 * @param httpClient the http client to customize.
+	 * @return the customized HttpClient.
+	 */
+	HttpClient customize(HttpClient httpClient);
+
+}

spring-cloud-gateway-core/src/test/java/org/springframework/cloud/gateway/config/GatewayAutoConfigurationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2019 the original author or authors.
+ * Copyright 2013-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,8 @@
 
 package org.springframework.cloud.gateway.config;
 
+import java.util.concurrent.atomic.AtomicBoolean;
+
 import org.junit.Test;
 import reactor.netty.http.client.HttpClient;
 
@@ -30,6 +32,8 @@ import org.springframework.boot.test.context.runner.ReactiveWebApplicationContex
 import org.springframework.cloud.gateway.actuate.GatewayControllerEndpoint;
 import org.springframework.cloud.gateway.actuate.GatewayLegacyControllerEndpoint;
 import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
 import org.springframework.web.filter.reactive.HiddenHttpMethodFilter;
 import org.springframework.web.reactive.socket.client.ReactorNettyWebSocketClient;
 
@@ -81,7 +85,7 @@ public class GatewayAutoConfigurationTests {
 				.withConfiguration(AutoConfigurations.of(WebFluxAutoConfiguration.class,
 						MetricsAutoConfiguration.class,
 						SimpleMetricsExportAutoConfiguration.class,
-						GatewayAutoConfiguration.class))
+						GatewayAutoConfiguration.class, HttpClientCustomizedConfig.class))
 				.withPropertyValues(
 						"spring.cloud.gateway.httpclient.ssl.use-insecure-trust-manager=true",
 						"spring.cloud.gateway.httpclient.connect-timeout=10",
@@ -113,6 +117,9 @@ public class GatewayAutoConfigurationTests {
 							.getBean(ReactorNettyWebSocketClient.class);
 					assertThat(webSocketClient.getMaxFramePayloadLength())
 							.isEqualTo(1024);
+					HttpClientCustomizedConfig config = context
+							.getBean(HttpClientCustomizedConfig.class);
+					assertThat(config.called.get()).isTrue();
 				});
 	}
 
@@ -143,4 +150,19 @@ public class GatewayAutoConfigurationTests {
 
 	}
 
+	@Configuration
+	protected static class HttpClientCustomizedConfig {
+
+		private final AtomicBoolean called = new AtomicBoolean();
+
+		@Bean
+		HttpClientCustomizer myCustomCustomizer() {
+			return httpClient -> {
+				called.compareAndSet(false, true);
+				return httpClient;
+			};
+		}
+
+	}
+
 }