Do not auto-configure RestTemplateBuilder in reactive web apps

Closes gh-15718

Author: wilkinsona

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/client/RestTemplateAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2018 the original author or authors.
+ * Copyright 2012-2019 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.
@@ -24,11 +24,16 @@
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication.Type;
+import org.springframework.boot.autoconfigure.condition.NoneNestedConditions;
 import org.springframework.boot.autoconfigure.http.HttpMessageConverters;
 import org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration;
+import org.springframework.boot.autoconfigure.web.client.RestTemplateAutoConfiguration.NotReactiveWebApplicationCondition;
 import org.springframework.boot.web.client.RestTemplateBuilder;
 import org.springframework.boot.web.client.RestTemplateCustomizer;
 import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Conditional;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.util.CollectionUtils;
 import org.springframework.web.client.RestTemplate;
@@ -43,6 +48,7 @@
 @Configuration
 @AutoConfigureAfter(HttpMessageConvertersAutoConfiguration.class)
 @ConditionalOnClass(RestTemplate.class)
+@Conditional(NotReactiveWebApplicationCondition.class)
 public class RestTemplateAutoConfiguration {
 
 	private final ObjectProvider<HttpMessageConverters> messageConverters;
@@ -73,4 +79,17 @@ public RestTemplateBuilder restTemplateBuilder() {
 		return builder;
 	}
 
+	static class NotReactiveWebApplicationCondition extends NoneNestedConditions {
+
+		NotReactiveWebApplicationCondition() {
+			super(ConfigurationPhase.PARSE_CONFIGURATION);
+		}
+
+		@ConditionalOnWebApplication(type = Type.REACTIVE)
+		private static class ReactiveWebApplication {
+
+		}
+
+	}
+
 }

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/client/RestTemplateAutoConfigurationTests.java

@@ -24,6 +24,8 @@
 import org.springframework.boot.autoconfigure.http.HttpMessageConverters;
 import org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration;
 import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+import org.springframework.boot.test.context.runner.ReactiveWebApplicationContextRunner;
+import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
 import org.springframework.boot.web.client.RestTemplateBuilder;
 import org.springframework.boot.web.client.RestTemplateCustomizer;
 import org.springframework.context.annotation.Bean;
@@ -124,6 +126,24 @@ public void builderShouldBeFreshForEachUse() {
 				.run((context) -> assertThat(context).hasNotFailed());
 	}
 
+	@Test
+	public void whenServletWebApplicationRestTemplateBuilderIsConfigured() {
+		new WebApplicationContextRunner()
+				.withConfiguration(
+						AutoConfigurations.of(RestTemplateAutoConfiguration.class))
+				.run((context) -> assertThat(context)
+						.hasSingleBean(RestTemplateBuilder.class));
+	}
+
+	@Test
+	public void whenReactiveWebApplicationRestTemplateIsNotConfigured() {
+		new ReactiveWebApplicationContextRunner()
+				.withConfiguration(
+						AutoConfigurations.of(RestTemplateAutoConfiguration.class))
+				.run((context) -> assertThat(context)
+						.doesNotHaveBean(RestTemplateBuilder.class));
+	}
+
 	@Configuration
 	static class RestTemplateConfig {