Use object provider for LoadBalancerRestClientPostProcessor (#1366)

Author: OlgaMaciaszek

spring-cloud-commons/src/main/java/org/springframework/cloud/client/loadbalancer/LoadBalancerAutoConfiguration.java

@@ -49,6 +49,7 @@
  * @author Will Tran
  * @author Gang Li
  * @author Olga Maciaszek-Sharma
+ * @author Henning Pöttker
  */
 @AutoConfiguration
 @Conditional(BlockingRestClassesPresentCondition.class)
@@ -86,17 +87,18 @@ static class DeferringLoadBalancerInterceptorConfig {
 
 		@Bean
 		@ConditionalOnMissingBean
-		public DeferringLoadBalancerInterceptor deferringLoadBalancerInterceptor(
+		public static DeferringLoadBalancerInterceptor deferringLoadBalancerInterceptor(
 				ObjectProvider<BlockingLoadBalancerInterceptor> loadBalancerInterceptorObjectProvider) {
 			return new DeferringLoadBalancerInterceptor(loadBalancerInterceptorObjectProvider);
 		}
 
 		@Bean
 		@ConditionalOnBean(DeferringLoadBalancerInterceptor.class)
-		@ConditionalOnMissingBean
-		LoadBalancerRestClientBuilderBeanPostProcessor lbRestClientPostProcessor(
-				DeferringLoadBalancerInterceptor loadBalancerInterceptor, ApplicationContext context) {
-			return new LoadBalancerRestClientBuilderBeanPostProcessor(loadBalancerInterceptor, context);
+		@ConditionalOnMissingBean(LoadBalancerRestClientBuilderBeanPostProcessor.class)
+		static LoadBalancerRestClientBuilderBeanPostProcessor<DeferringLoadBalancerInterceptor> lbRestClientPostProcessor(
+				ObjectProvider<DeferringLoadBalancerInterceptor> loadBalancerInterceptorProvider,
+				ApplicationContext context) {
+			return new LoadBalancerRestClientBuilderBeanPostProcessor<>(loadBalancerInterceptorProvider, context);
 		}
 
 	}

spring-cloud-commons/src/main/java/org/springframework/cloud/client/loadbalancer/LoadBalancerRestClientBuilderBeanPostProcessor.java

@@ -17,6 +17,7 @@
 package org.springframework.cloud.client.loadbalancer;
 
 import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.beans.factory.config.BeanPostProcessor;
 import org.springframework.context.ApplicationContext;
 import org.springframework.http.client.ClientHttpRequestInterceptor;
@@ -29,15 +30,21 @@
  * @author Olga Maciaszek-Sharma
  * @since 4.1.0
  */
-public class LoadBalancerRestClientBuilderBeanPostProcessor implements BeanPostProcessor {
+public class LoadBalancerRestClientBuilderBeanPostProcessor<T extends ClientHttpRequestInterceptor>
+		implements BeanPostProcessor {
 
-	private final ClientHttpRequestInterceptor loadBalancerInterceptor;
+	private final ObjectProvider<T> loadBalancerInterceptorProvider;
 
 	private final ApplicationContext context;
 
-	public LoadBalancerRestClientBuilderBeanPostProcessor(ClientHttpRequestInterceptor loadBalancerInterceptor,
+	public LoadBalancerRestClientBuilderBeanPostProcessor(T loadBalancerInterceptor, ApplicationContext context) {
+		this.loadBalancerInterceptorProvider = new SimpleObjectProvider<>(loadBalancerInterceptor);
+		this.context = context;
+	}
+
+	public LoadBalancerRestClientBuilderBeanPostProcessor(ObjectProvider<T> loadBalancerInterceptorProvider,
 			ApplicationContext context) {
-		this.loadBalancerInterceptor = loadBalancerInterceptor;
+		this.loadBalancerInterceptorProvider = loadBalancerInterceptorProvider;
 		this.context = context;
 	}
 
@@ -47,7 +54,11 @@ public Object postProcessBeforeInitialization(Object bean, String beanName) thro
 			if (context.findAnnotationOnBean(beanName, LoadBalanced.class) == null) {
 				return bean;
 			}
-			((RestClient.Builder) bean).requestInterceptor(loadBalancerInterceptor);
+			ClientHttpRequestInterceptor interceptor = loadBalancerInterceptorProvider.getIfAvailable();
+			if (interceptor == null) {
+				throw new IllegalStateException(ClientHttpRequestInterceptor.class.getSimpleName() + " not available.");
+			}
+			((RestClient.Builder) bean).requestInterceptor(interceptor);
 		}
 		return bean;
 	}

spring-cloud-commons/src/main/java/org/springframework/cloud/client/loadbalancer/SimpleObjectProvider.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2012-2024 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.client.loadbalancer;
+
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.ObjectProvider;
+import org.springframework.cloud.client.loadbalancer.reactive.LoadBalancerWebClientBuilderBeanPostProcessor;
+
+/**
+ * Wrapper for {@link ObjectProvider}. Added to use for a workaround in
+ * {@link LoadBalancerWebClientBuilderBeanPostProcessor}.
+ *
+ * @param <T> type of the object to fetch
+ * @author Spencer Gibb
+ * @deprecated for removal in 4.0
+ */
+@Deprecated(forRemoval = true)
+public class SimpleObjectProvider<T> implements ObjectProvider<T> {
+
+	private final T object;
+
+	public SimpleObjectProvider(T object) {
+		this.object = object;
+	}
+
+	@Override
+	public T getObject(Object... args) throws BeansException {
+		return this.object;
+	}
+
+	@Override
+	public T getIfAvailable() throws BeansException {
+		return this.object;
+	}
+
+	@Override
+	public T getIfUnique() throws BeansException {
+		return this.object;
+	}
+
+	@Override
+	public T getObject() throws BeansException {
+		return this.object;
+	}
+
+}

spring-cloud-commons/src/main/java/org/springframework/cloud/client/loadbalancer/reactive/DeferringLoadBalancerExchangeFilterFunction.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2024 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.
@@ -55,7 +55,7 @@ void tryResolveDelegate() {
 		if (delegate == null) {
 			delegate = exchangeFilterFunctionProvider.getIfAvailable();
 			if (delegate == null) {
-				throw new IllegalStateException("ReactorLoadBalancerExchangeFilterFunction not available.");
+				throw new IllegalStateException("LoadBalancer ExchangeFilterFunction not available.");
 			}
 		}
 	}

spring-cloud-commons/src/main/java/org/springframework/cloud/client/loadbalancer/reactive/LoadBalancerBeanPostProcessorAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2024 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.
@@ -39,16 +39,19 @@
  * beans.
  *
  * @author Olga Maciaszek-Sharma
+ * @author Henning Pöttker
  * @since 2.2.0
  */
 @Configuration(proxyBeanMethods = false)
 @ConditionalOnClass(WebClient.class)
 @Conditional(LoadBalancerBeanPostProcessorAutoConfiguration.OnAnyLoadBalancerImplementationPresentCondition.class)
 public class LoadBalancerBeanPostProcessorAutoConfiguration {
 
+	@SuppressWarnings("rawtypes")
 	@Bean
-	public LoadBalancerWebClientBuilderBeanPostProcessor loadBalancerWebClientBuilderBeanPostProcessor(
-			DeferringLoadBalancerExchangeFilterFunction deferringExchangeFilterFunction, ApplicationContext context) {
+	public static LoadBalancerWebClientBuilderBeanPostProcessor loadBalancerWebClientBuilderBeanPostProcessor(
+			ObjectProvider<DeferringLoadBalancerExchangeFilterFunction> deferringExchangeFilterFunction,
+			ApplicationContext context) {
 		return new LoadBalancerWebClientBuilderBeanPostProcessor(deferringExchangeFilterFunction, context);
 	}
 
@@ -58,7 +61,7 @@ protected static class ReactorDeferringLoadBalancerFilterConfig {
 
 		@Bean
 		@Primary
-		DeferringLoadBalancerExchangeFilterFunction<LoadBalancedExchangeFilterFunction> reactorDeferringLoadBalancerExchangeFilterFunction(
+		static DeferringLoadBalancerExchangeFilterFunction<LoadBalancedExchangeFilterFunction> reactorDeferringLoadBalancerExchangeFilterFunction(
 				ObjectProvider<LoadBalancedExchangeFilterFunction> exchangeFilterFunctionProvider) {
 			return new DeferringLoadBalancerExchangeFilterFunction<>(exchangeFilterFunctionProvider);
 		}

spring-cloud-commons/src/main/java/org/springframework/cloud/client/loadbalancer/reactive/LoadBalancerWebClientBuilderBeanPostProcessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2024 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.
@@ -17,8 +17,10 @@
 package org.springframework.cloud.client.loadbalancer.reactive;
 
 import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.beans.factory.config.BeanPostProcessor;
 import org.springframework.cloud.client.loadbalancer.LoadBalanced;
+import org.springframework.cloud.client.loadbalancer.SimpleObjectProvider;
 import org.springframework.context.ApplicationContext;
 import org.springframework.web.reactive.function.client.WebClient;
 
@@ -30,15 +32,28 @@
  * @author Olga Maciaszek-Sharma
  * @since 2.2.0
  */
+@SuppressWarnings({ "removal", "rawtypes" })
 public class LoadBalancerWebClientBuilderBeanPostProcessor implements BeanPostProcessor {
 
-	private final DeferringLoadBalancerExchangeFilterFunction exchangeFilterFunction;
+	private final ObjectProvider<DeferringLoadBalancerExchangeFilterFunction> exchangeFilterFunctionObjectProvider;
 
 	private final ApplicationContext context;
 
+	/**
+	 * @deprecated in favour of
+	 * {@link LoadBalancerWebClientBuilderBeanPostProcessor#LoadBalancerWebClientBuilderBeanPostProcessor(ObjectProvider, ApplicationContext)}
+	 */
+	@Deprecated(forRemoval = true)
 	public LoadBalancerWebClientBuilderBeanPostProcessor(
 			DeferringLoadBalancerExchangeFilterFunction exchangeFilterFunction, ApplicationContext context) {
-		this.exchangeFilterFunction = exchangeFilterFunction;
+		this.exchangeFilterFunctionObjectProvider = new SimpleObjectProvider<>(exchangeFilterFunction);
+		this.context = context;
+	}
+
+	public LoadBalancerWebClientBuilderBeanPostProcessor(
+			ObjectProvider<DeferringLoadBalancerExchangeFilterFunction> exchangeFilterFunction,
+			ApplicationContext context) {
+		this.exchangeFilterFunctionObjectProvider = exchangeFilterFunction;
 		this.context = context;
 	}
 
@@ -48,7 +63,12 @@ public Object postProcessBeforeInitialization(Object bean, String beanName) thro
 			if (context.findAnnotationOnBean(beanName, LoadBalanced.class) == null) {
 				return bean;
 			}
-			((WebClient.Builder) bean).filter(exchangeFilterFunction);
+			DeferringLoadBalancerExchangeFilterFunction exchangeFilterFunction = exchangeFilterFunctionObjectProvider
+				.getIfAvailable();
+			if (exchangeFilterFunction == null) {
+				throw new IllegalStateException("LoadBalancerExchangeFilterFunction not found");
+			}
+			((WebClient.Builder) bean).filter(exchangeFilterFunctionObjectProvider.getIfAvailable());
 		}
 		return bean;
 	}