Add libraries actuator endpoint

Adds a libraries actuator endpoint that displays details about the libraries used by the application.
Provides out-of-the-box support for displaying details about Java libraries that are bundled within the application jar/war archive.

The spring-boot-maven-plugin and spring-boot-gradle-plugin now generate a META-INF/bundled-libraries.yaml file when they package the application archive.
The file is included in the packaged application archive.

At runtime, libraries are contributed to the libraries endpoint via LibrariesContributor beans, similar to how InfoContributers contribute to the info endpoint.

spring-boot-actuator-autoconfigure auto-configures a LibrariesContributor that adds the libraries from META-INF/bundled-libraries.yaml to the libraries endpoint.
This auto-configuration can be disabled using environment properties similar to how other actuator endpoints behave.

An application can provide other LibrariesContributor instances to contribute more libraries to the libraries endpoint.
For example, an application might want to contribute libraries dynamically added at runtime.
Or an application might want to contribute details about front-end libraries.

Each Library is described as a simple set of key/value pairs.
For example, Java libraries with coordinates in a Maven repository typically contain entries for `groupId`, `artifactId`, and `version`.

Fixes #22924

Author: philsttr

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/libraries/ConditionalOnEnabledLibrariesContributor.java

@@ -0,0 +1,49 @@
+/*
+ * 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.libraries;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.springframework.context.annotation.Conditional;
+
+/**
+ * {@link Conditional @Conditional} that checks whether or not a default libraries
+ * contributor is enabled. Matches if the value of the
+ * {@code management.libraries.<name>.enabled} property is {@code true}. Otherwise,
+ * matches if the value of the {@code management.libraries.defaults.enabled} property is
+ * {@code true} or if it is not configured.
+ *
+ * @author Phil Clay
+ * @since 2.5.0
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ ElementType.TYPE, ElementType.METHOD })
+@Documented
+@Conditional(OnEnabledLibrariesContributorCondition.class)
+public @interface ConditionalOnEnabledLibrariesContributor {
+
+	/**
+	 * The name of the libraries contributor.
+	 * @return the name of the libraries contributor
+	 */
+	String value();
+
+}

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/libraries/LibrariesEndpointAutoConfiguration.java

@@ -0,0 +1,79 @@
+/*
+ * 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.libraries;
+
+import java.io.IOException;
+import java.util.stream.Collectors;
+
+import org.springframework.beans.factory.ObjectProvider;
+import org.springframework.boot.actuate.autoconfigure.endpoint.condition.ConditionalOnAvailableEndpoint;
+import org.springframework.boot.actuate.autoconfigure.libraries.LibrariesProperties.Bundled;
+import org.springframework.boot.actuate.libraries.BasicLibrariesContributor;
+import org.springframework.boot.actuate.libraries.LibrariesContributor;
+import org.springframework.boot.actuate.libraries.LibrariesEndpoint;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnResource;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.core.Ordered;
+import org.springframework.core.annotation.Order;
+
+/**
+ * {@link EnableAutoConfiguration Auto-configuration} for the {@link LibrariesEndpoint}.
+ *
+ * @author Phil Clay
+ * @since 2.5.0
+ */
+@Configuration(proxyBeanMethods = false)
+@EnableConfigurationProperties(LibrariesProperties.class)
+@ConditionalOnAvailableEndpoint(endpoint = LibrariesEndpoint.class)
+public class LibrariesEndpointAutoConfiguration {
+
+	/**
+	 * The default order for the core {@link LibrariesContributor} beans.
+	 */
+	public static final int DEFAULT_ORDER = Ordered.HIGHEST_PRECEDENCE + 10;
+
+	/**
+	 * A {@link LibrariesContributor} that contributes libraries that were bundled in the
+	 * spring boot application at build time, typically by the spring boot maven or gradle
+	 * plugins.
+	 * @param librariesProperties libraries configuration properties
+	 * @return a {@link LibrariesContributor} that contributes libraries that were bundled
+	 * in the spring boot application at build time, typically by the spring boot maven or
+	 * gradle plugins.
+	 * @throws IOException if an exception occurs reading the build libraries yaml file
+	 */
+	@Bean
+	@ConditionalOnEnabledLibrariesContributor("bundled")
+	@ConditionalOnResource(resources = "${" + LibrariesProperties.CONFIGURATION_PROPERTIES_PREFIX
+			+ ".bundled.location:classpath:" + Bundled.DEFAULT_CLASSPATH_LOCATION + "}")
+	@Order(DEFAULT_ORDER)
+	public LibrariesContributor bundledLibrariesContributor(LibrariesProperties librariesProperties)
+			throws IOException {
+		return BasicLibrariesContributor.fromYamlResource("bundled", librariesProperties.getBundled().getLocation());
+	}
+
+	@Bean
+	@ConditionalOnMissingBean
+	public LibrariesEndpoint librariesEndpoint(ObjectProvider<LibrariesContributor> librariesContributors) {
+		return new LibrariesEndpoint(librariesContributors.orderedStream().collect(Collectors.toList()));
+	}
+
+}

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/libraries/LibrariesProperties.java

@@ -0,0 +1,90 @@
+/*
+ * 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.libraries;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.core.io.Resource;
+
+/**
+ * Configuration properties for core libraries contributors.
+ *
+ * @author Phil Clay
+ * @since 2.5.0
+ */
+@ConfigurationProperties(LibrariesProperties.CONFIGURATION_PROPERTIES_PREFIX)
+public class LibrariesProperties {
+
+	static final String CONFIGURATION_PROPERTIES_PREFIX = "management.libraries";
+
+	private final Bundled bundled = new Bundled();
+
+	/**
+	 * Gets the properties for exposing the libraries bundled in the application archive,
+	 * typically by the spring boot maven or gradle plugins.
+	 * @return the properties for exposing the libraries bundled in the application
+	 * archive
+	 */
+	public Bundled getBundled() {
+		return this.bundled;
+	}
+
+	/**
+	 * Properties for exposing the libraries bundled in the application archive, typically
+	 * by the spring boot maven or gradle plugins.
+	 */
+	public static class Bundled {
+
+		/**
+		 * The default classpath location of the {@code bundled-libraries.yaml} file. This
+		 * location is where the spring boot maven and gradle plugins will write the
+		 * {@code bundled-libraries.yaml} file within the jar/war.
+		 */
+		public static final String DEFAULT_CLASSPATH_LOCATION = "META-INF/bundled-libraries.yaml";
+
+		/**
+		 * Location of the generated {@code bundled-libraries.yaml} file.
+		 */
+		private Resource location = new ClassPathResource(DEFAULT_CLASSPATH_LOCATION);
+
+		/**
+		 * Gets the location of the generated {@code bundled-libraries.yaml} file.
+		 *
+		 * <p>
+		 * Defaults to {@value #DEFAULT_CLASSPATH_LOCATION}.
+		 * </p>
+		 * @return the location of the generated {@code bundled-libraries.yaml} file.
+		 */
+		public Resource getLocation() {
+			return this.location;
+		}
+
+		/**
+		 * Sets the location of the generated {@code bundled-libraries.yaml} file.
+		 * <p>
+		 * Defaults to {@value #DEFAULT_CLASSPATH_LOCATION}.
+		 * </p>
+		 * @param location the location of the generated {@code bundled-libraries.yaml}
+		 * file.
+		 */
+		public void setLocation(Resource location) {
+			this.location = location;
+		}
+
+	}
+
+}

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/libraries/OnEnabledLibrariesContributorCondition.java

@@ -0,0 +1,33 @@
+/*
+ * 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.libraries;
+
+import org.springframework.boot.actuate.autoconfigure.OnEndpointElementCondition;
+import org.springframework.context.annotation.Condition;
+
+/**
+ * {@link Condition} that checks if a libraries contributor is enabled.
+ *
+ * @author Phil Clay
+ */
+class OnEnabledLibrariesContributorCondition extends OnEndpointElementCondition {
+
+	OnEnabledLibrariesContributorCondition() {
+		super("management.libraries.", ConditionalOnEnabledLibrariesContributor.class);
+	}
+
+}

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/libraries/package-info.java

@@ -0,0 +1,20 @@
+/*
+ * 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.
+ */
+
+/**
+ * Auto-configuration for actuator libraries concerns.
+ */
+package org.springframework.boot.actuate.autoconfigure.libraries;

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -273,6 +273,12 @@
       "name": "management.info.git.mode",
       "defaultValue": "simple"
     },
+    {
+      "name": "management.libraries.bundled.enabled",
+      "type": "java.lang.Boolean",
+      "description": "Whether the libraries endpoint should show the libraries bundled in the application archive.",
+      "defaultValue": true
+    },
     {
       "name": "management.metrics.binders.files.enabled",
       "type": "java.lang.Boolean",

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

@@ -33,6 +33,7 @@ org.springframework.boot.actuate.autoconfigure.jdbc.DataSourceHealthContributorA
 org.springframework.boot.actuate.autoconfigure.jms.JmsHealthContributorAutoConfiguration,\
 org.springframework.boot.actuate.autoconfigure.jolokia.JolokiaEndpointAutoConfiguration,\
 org.springframework.boot.actuate.autoconfigure.ldap.LdapHealthContributorAutoConfiguration,\
+org.springframework.boot.actuate.autoconfigure.libraries.LibrariesEndpointAutoConfiguration,\
 org.springframework.boot.actuate.autoconfigure.liquibase.LiquibaseEndpointAutoConfiguration,\
 org.springframework.boot.actuate.autoconfigure.logging.LogFileWebEndpointAutoConfiguration,\
 org.springframework.boot.actuate.autoconfigure.logging.LoggersEndpointAutoConfiguration,\