Disable ReactorResourceFactory use of global resources in tests

Add `ContextCustomizerFactory` to automatically disable the use of
`ReactorResourceFactory` global resources in tests.

Fixes gh-38199

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/web/reactor/netty/DisableReactorResourceFactoryGlobalResourcesBeanPostProcessor.java

@@ -0,0 +1,39 @@
+/*
+ * 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.boot.test.web.reactor.netty;
+
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.config.BeanPostProcessor;
+import org.springframework.http.client.ReactorResourceFactory;
+
+/**
+ * {@link BeanPostProcessor} to disable the use of global resources in
+ * {@link ReactorResourceFactory} preventing test cleanup issues.
+ *
+ * @author Phillip Webb
+ */
+class DisableReactorResourceFactoryGlobalResourcesBeanPostProcessor implements BeanPostProcessor {
+
+	@Override
+	public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
+		if (bean instanceof ReactorResourceFactory reactorResourceFactory) {
+			reactorResourceFactory.setUseGlobalResources(false);
+		}
+		return bean;
+	}
+
+}

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/web/reactor/netty/DisableReactorResourceFactoryGlobalResourcesContextCustomizerFactory.java

@@ -0,0 +1,74 @@
+/*
+ * 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.boot.test.web.reactor.netty;
+
+import java.util.List;
+
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.http.client.ReactorResourceFactory;
+import org.springframework.test.context.ContextConfigurationAttributes;
+import org.springframework.test.context.ContextCustomizer;
+import org.springframework.test.context.ContextCustomizerFactory;
+import org.springframework.test.context.MergedContextConfiguration;
+import org.springframework.util.ClassUtils;
+
+/**
+ * {@link ContextCustomizerFactory} to disable the use of global resources in
+ * {@link ReactorResourceFactory} preventing test cleanup issues.
+ *
+ * @author Phillip Webb
+ */
+class DisableReactorResourceFactoryGlobalResourcesContextCustomizerFactory implements ContextCustomizerFactory {
+
+	String REACTOR_RESOURCE_FACTORY_CLASS = "org.springframework.http.client.ReactorResourceFactory";
+
+	@Override
+	public ContextCustomizer createContextCustomizer(Class<?> testClass,
+			List<ContextConfigurationAttributes> configAttributes) {
+		if (ClassUtils.isPresent(this.REACTOR_RESOURCE_FACTORY_CLASS, testClass.getClassLoader())) {
+			return new DisableReactorResourceFactoryGlobalResourcesContextCustomizerCustomizer();
+		}
+		return null;
+
+	}
+
+	static final class DisableReactorResourceFactoryGlobalResourcesContextCustomizerCustomizer
+			implements ContextCustomizer {
+
+		private DisableReactorResourceFactoryGlobalResourcesContextCustomizerCustomizer() {
+		}
+
+		@Override
+		public void customizeContext(ConfigurableApplicationContext context, MergedContextConfiguration mergedConfig) {
+			context.getBeanFactory()
+				.registerSingleton(DisableReactorResourceFactoryGlobalResourcesBeanPostProcessor.class.getName(),
+						new DisableReactorResourceFactoryGlobalResourcesBeanPostProcessor());
+		}
+
+		@Override
+		public boolean equals(Object obj) {
+			return (obj instanceof DisableReactorResourceFactoryGlobalResourcesContextCustomizerCustomizer);
+		}
+
+		@Override
+		public int hashCode() {
+			return getClass().hashCode();
+		}
+
+	}
+
+}

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/web/reactor/netty/package-info.java

@@ -0,0 +1,20 @@
+/*
+ * 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.
+ */
+
+/**
+ * Spring Boot support for testing Reactor Netty.
+ */
+package org.springframework.boot.test.web.reactor.netty;

spring-boot-project/spring-boot-test/src/main/resources/META-INF/spring.factories

@@ -6,7 +6,8 @@ org.springframework.boot.test.graphql.tester.HttpGraphQlTesterContextCustomizerF
 org.springframework.boot.test.json.DuplicateJsonObjectContextCustomizerFactory,\
 org.springframework.boot.test.mock.mockito.MockitoContextCustomizerFactory,\
 org.springframework.boot.test.web.client.TestRestTemplateContextCustomizerFactory,\
-org.springframework.boot.test.web.reactive.server.WebTestClientContextCustomizerFactory
+org.springframework.boot.test.web.reactive.server.WebTestClientContextCustomizerFactory,\
+org.springframework.boot.test.web.reactor.netty.DisableReactorResourceFactoryGlobalResourcesContextCustomizerFactory
 
 # Test Execution Listeners
 org.springframework.test.context.TestExecutionListener=\

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/web/reactor/netty/DisableReactorResourceFactoryGlobalResourcesContextCustomizerFactoryTests.java

@@ -0,0 +1,55 @@
+/*
+ * 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.boot.test.web.reactor.netty;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.http.client.ReactorResourceFactory;
+import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link DisableReactorResourceFactoryGlobalResourcesContextCustomizerFactory}.
+ *
+ * @author Phillip Webb
+ */
+@SpringJUnitConfig
+class DisableReactorResourceFactoryGlobalResourcesContextCustomizerFactoryTests {
+
+	@Autowired
+	private ReactorResourceFactory reactorResourceFactory;
+
+	@Test
+	void disablesUseGlobalResources() {
+		assertThat(this.reactorResourceFactory.isUseGlobalResources()).isFalse();
+	}
+
+	@Configuration
+	static class Config {
+
+		@Bean
+		ReactorResourceFactory reactorResourceFactory() {
+			return new ReactorResourceFactory();
+		}
+
+	}
+
+}