Disable all mappings endpoint infra when endpoint is unavailable

Previously, when the mappings endpoint was not available, the beans
that provide mapping descriptions were still created. This resulted
in unnecessary CPU and memory usage collecting and storing
information that would never by used.

This commit updates the auto-configuration for the mappings endpoint
so that all the beans that it creates are conditional on the endpoint
being available, rather than only the endpoint bean itself.

Closes gh-23977

Author: wilkinsona

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/web/mappings/MappingsEndpointAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -44,10 +44,10 @@
  * @since 2.0.0
  */
 @Configuration(proxyBeanMethods = false)
+@ConditionalOnAvailableEndpoint(endpoint = MappingsEndpoint.class)
 public class MappingsEndpointAutoConfiguration {
 
 	@Bean
-	@ConditionalOnAvailableEndpoint
 	public MappingsEndpoint mappingsEndpoint(ApplicationContext applicationContext,
 			ObjectProvider<MappingDescriptionProvider> descriptionProviders) {
 		return new MappingsEndpoint(descriptionProviders.orderedStream().collect(Collectors.toList()),

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/web/mappings/MappingsEndpointAutoConfigurationTests.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2012-2021 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.actuate.autoconfigure.web.mappings;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.actuate.autoconfigure.endpoint.EndpointAutoConfiguration;
+import org.springframework.boot.actuate.autoconfigure.endpoint.web.WebEndpointAutoConfiguration;
+import org.springframework.boot.actuate.autoconfigure.endpoint.web.servlet.WebMvcEndpointManagementContextConfiguration;
+import org.springframework.boot.actuate.web.mappings.MappingDescriptionProvider;
+import org.springframework.boot.actuate.web.mappings.MappingsEndpoint;
+import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration;
+import org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration;
+import org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration;
+import org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration;
+import org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration;
+import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link MappingsEndpointAutoConfiguration}.
+ *
+ * @author Andy Wilkinson
+ */
+public class MappingsEndpointAutoConfigurationTests {
+
+	@Test
+	public void whenEndpointIsUnavailableThenEndpointAndDescriptionProvidersAreNotCreated() {
+		new WebApplicationContextRunner()
+				.withConfiguration(AutoConfigurations.of(MappingsEndpointAutoConfiguration.class,
+						JacksonAutoConfiguration.class, HttpMessageConvertersAutoConfiguration.class,
+						WebMvcAutoConfiguration.class, DispatcherServletAutoConfiguration.class,
+						EndpointAutoConfiguration.class, WebEndpointAutoConfiguration.class,
+						WebMvcEndpointManagementContextConfiguration.class, PropertyPlaceholderAutoConfiguration.class))
+				.run((context) -> {
+					assertThat(context).doesNotHaveBean(MappingsEndpoint.class);
+					assertThat(context).doesNotHaveBean(MappingDescriptionProvider.class);
+				});
+
+	}
+
+	@Test
+	public void whenEndpointIsAvailableThenEndpointAndDescriptionProvidersAreCreated() {
+		new WebApplicationContextRunner()
+				.withConfiguration(AutoConfigurations.of(MappingsEndpointAutoConfiguration.class,
+						JacksonAutoConfiguration.class, HttpMessageConvertersAutoConfiguration.class,
+						WebMvcAutoConfiguration.class, DispatcherServletAutoConfiguration.class,
+						EndpointAutoConfiguration.class, WebEndpointAutoConfiguration.class,
+						WebMvcEndpointManagementContextConfiguration.class, PropertyPlaceholderAutoConfiguration.class))
+				.withPropertyValues("management.endpoints.web.exposure.include=mappings").run((context) -> {
+					assertThat(context).hasSingleBean(MappingsEndpoint.class);
+					assertThat(context.getBeansOfType(MappingDescriptionProvider.class)).hasSize(3);
+				});
+
+	}
+
+}