Add HealthEndpointGroupsRegistry and its Customizer

Prior to this commit, `HealthContributor` would be exposed under the
main `HealthEndpoint` and subgroups, `HealthEndpointGroups`. Groups are
driven by configuration properties and there was no way to contribute
programmatically new groups.

This commit introduces the `HealthEndpointGroupsRegistry` (a mutable
version of `HealthEndpointGroups`) and a
`HealthEndpointGroupsRegistryCustomizer`. This allows configurations to
add/remove groups during Actuator auto-configuration.

Closes gh-20554

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/health/HealthEndpointGroup.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -23,6 +23,7 @@ import org.springframework.boot.actuate.endpoint.SecurityContext;
  * by the {@link HealthEndpoint}.
  *
  * @author Phillip Webb
+ * @author Brian Clozel
  * @since 2.2.0
  */
 public interface HealthEndpointGroup {
@@ -62,4 +63,27 @@ public interface HealthEndpointGroup {
 	 */
 	HttpCodeStatusMapper getHttpCodeStatusMapper();
 
+	/**
+	 * Options for showing items in responses from the {@link HealthEndpointGroup} web
+	 * extensions.
+	 */
+	enum Show {
+
+		/**
+		 * Never show the item in the response.
+		 */
+		NEVER,
+
+		/**
+		 * Show the item in the response when accessed by an authorized user.
+		 */
+		WHEN_AUTHORIZED,
+
+		/**
+		 * Always show the item in the response.
+		 */
+		ALWAYS
+
+	}
+
 }

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/health/HealthEndpointGroupConfigurer.java

@@ -0,0 +1,84 @@
+/*
+ * Copyright 2012-2020 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.health;
+
+import org.springframework.boot.actuate.health.HealthEndpointGroup.Show;
+
+/**
+ * A configurer for customizing an {@link HealthEndpointGroup} being built.
+ *
+ * @author Brian Clozel
+ * @since 2.3.0
+ */
+public interface HealthEndpointGroupConfigurer {
+
+	/**
+	 * Configure the indicator endpoint ids to include in this group.
+	 * @param indicators the indicator endpoint ids
+	 * @return the configurer instance
+	 */
+	HealthEndpointGroupConfigurer include(String... indicators);
+
+	/**
+	 * Configure the indicator endpoint ids to exclude from this group.
+	 * @param indicators the indicator endpoint ids
+	 * @return the configurer instance
+	 */
+	HealthEndpointGroupConfigurer exclude(String... indicators);
+
+	/**
+	 * Configure the {@link StatusAggregator} to use for this group.
+	 * <p>
+	 * If none set, this will default to the globalmy configured {@link StatusAggregator}.
+	 * @param statusAggregator the status aggregator
+	 * @return the configurer instance
+	 */
+	HealthEndpointGroupConfigurer statusAggregator(StatusAggregator statusAggregator);
+
+	/**
+	 * Configure the {@link HttpCodeStatusMapper} to use for this group.
+	 * <p>
+	 * If none set, this will default to the globalmy configured
+	 * {@link HttpCodeStatusMapper}.
+	 * @param httpCodeStatusMapper the status code mapper
+	 * @return the configurer instance
+	 */
+	HealthEndpointGroupConfigurer httpCodeStatusMapper(HttpCodeStatusMapper httpCodeStatusMapper);
+
+	/**
+	 * Configure the {@link Show visbility option} for showing components of this group.
+	 * @param showComponents the components visibility
+	 * @return the configurer instance
+	 */
+	HealthEndpointGroupConfigurer showComponents(Show showComponents);
+
+	/**
+	 * Configure the {@link Show visbility option} for showing details of this group.
+	 * @param showDetails the details visibility
+	 * @return the configurer instance
+	 */
+	HealthEndpointGroupConfigurer showDetails(Show showDetails);
+
+	/**
+	 * Configure roles used to determine whether or not a user is authorized to be shown
+	 * details.
+	 * @param roles the roles
+	 * @return the configurer instance
+	 */
+	HealthEndpointGroupConfigurer roles(String... roles);
+
+}

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/health/HealthEndpointGroupsRegistry.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2012-2020 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.health;
+
+import java.util.function.Consumer;
+
+/**
+ * Builder for an {@link HealthEndpointGroups} immutable instance.
+ *
+ * @author Brian Clozel
+ * @since 2.3.0
+ */
+public interface HealthEndpointGroupsRegistry extends HealthEndpointGroups {
+
+	/**
+	 * Add a new {@link HealthEndpointGroup}.
+	 * @param groupName the name of the group to add
+	 * @param builder the group to add
+	 * @return the builder instance
+	 */
+	HealthEndpointGroupsRegistry add(String groupName, Consumer<HealthEndpointGroupConfigurer> builder);
+
+	/**
+	 * Remove an existing {@link HealthEndpointGroup}.
+	 * @param groupName the name of the group to remove
+	 * @return the builder instance
+	 */
+	HealthEndpointGroupsRegistry remove(String groupName);
+
+	/**
+	 * Build an immutable {@link HealthEndpointGroups}.
+	 * @return the {@link HealthEndpointGroups}
+	 */
+	HealthEndpointGroups toGroups();
+
+}

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/health/HealthEndpointGroupsRegistryCustomizer.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2012-2020 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.health;
+
+/**
+ * Callback interface that can be used to customize a
+ * {@link HealthEndpointGroupsRegistry}.
+ *
+ * @author Brian Clozel
+ * @since 2.3.0
+ */
+@FunctionalInterface
+public interface HealthEndpointGroupsRegistryCustomizer {
+
+	/**
+	 * Callback to customize a {@link HealthEndpointGroupsRegistry} instance.
+	 * @param healthEndpointGroupsRegistry the registry to customize
+	 */
+	void customize(HealthEndpointGroupsRegistry healthEndpointGroupsRegistry);
+
+}