Add HealthContributor and refactor HealthEndpoint

Overhaul `HealthEndpoint` support to make it easier to support health
groups. Prior to this commit the `HealthIndicator` interface was used
for both regular indicators and composite indicators. In addition the
`Health` result was used to both represent individual, system and
composite health. This design unfortunately means that all health
contributors need to be aware of the `HealthAggregator` and could not
easily support heath groups if per-group aggregation is required.

This commit reworks many aspects of the health support in order to
provide a cleaner separation between a `HealthIndicator`and a
composite. The following changes have been made:

- A `HealthContributor` interface has been introduced to represent
  the general concept of something that contributes health information.
  A contributor can either be a `HealthIndicator` or a
  `CompositeHealthContributor`.

- A `HealthComponent` class has been introduced to mirror the
  contributor arrangement. The component can be either
  `CompositeHealth` or `Health`.

- The `HealthAggregator` interface has been replaced with a more
  focused `StatusAggregator` interface which only deals with `Status`
  results.

- `CompositeHealthIndicator` has been replaced with
  `CompositeHealthContributor` which only provides access to other
  contributors. A composite can no longer directly return `Health`.

- `HealthIndicatorRegistry` has been replaced with
  `HealthContributorRegistry` and the default implementation now
  uses a copy-on-write strategy.

- `HealthEndpoint`, `HealthEndpointWebExtension` and
  `ReactiveHealthEndpointWebExtension` now extend a common
  `HealthEndpointSupport` class. They are now driven by a
  health contributor registry and `HealthEndpointSettings`.

- The `HealthStatusHttpMapper` class has been replaced by a
  `HttpCodeStatusMapper` interface.

- The `HealthWebEndpointResponseMapper` class has been replaced
  by a `HealthEndpointSettings` strategy. This allows us to move
  role related logic and `ShowDetails` to the auto-configure module.

- `SimpleHttpCodeStatusMapper` and `SimpleStatusAggregator`
  implementations have been added which are configured via constructor
  arguments rather than setters.

- Endpoint auto-configuration has been reworked and the
  `CompositeHealthIndicatorConfiguration` class has been replaced
  by `CompositeHealthContributorConfiguration`.

- The endpoint JSON has been changed make `details` distinct from
  `components`.

See spring-projectsgh-17926

Author: philwebb

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/cloudfoundry/reactive/CloudFoundryReactiveHealthEndpointWebExtension.java

@@ -19,13 +19,15 @@
 import reactor.core.publisher.Mono;
 
 import org.springframework.boot.actuate.autoconfigure.cloudfoundry.EndpointCloudFoundryExtension;
+import org.springframework.boot.actuate.endpoint.SecurityContext;
 import org.springframework.boot.actuate.endpoint.annotation.EndpointExtension;
 import org.springframework.boot.actuate.endpoint.annotation.ReadOperation;
+import org.springframework.boot.actuate.endpoint.annotation.Selector;
+import org.springframework.boot.actuate.endpoint.annotation.Selector.Match;
 import org.springframework.boot.actuate.endpoint.web.WebEndpointResponse;
-import org.springframework.boot.actuate.health.Health;
+import org.springframework.boot.actuate.health.HealthComponent;
 import org.springframework.boot.actuate.health.HealthEndpoint;
 import org.springframework.boot.actuate.health.ReactiveHealthEndpointWebExtension;
-import org.springframework.boot.actuate.health.ShowDetails;
 
 /**
  * Reactive {@link EndpointExtension @EndpointExtension} for the {@link HealthEndpoint}
@@ -44,8 +46,14 @@ public CloudFoundryReactiveHealthEndpointWebExtension(ReactiveHealthEndpointWebE
 	}
 
 	@ReadOperation
-	public Mono<WebEndpointResponse<Health>> health() {
-		return this.delegate.health(null, ShowDetails.ALWAYS);
+	public Mono<WebEndpointResponse<? extends HealthComponent>> health() {
+		return this.delegate.health(SecurityContext.NONE, true);
+	}
+
+	@ReadOperation
+	public Mono<WebEndpointResponse<? extends HealthComponent>> health(
+			@Selector(match = Match.ALL_REMAINING) String... path) {
+		return this.delegate.health(SecurityContext.NONE, true, path);
 	}
 
 }

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/cloudfoundry/servlet/CloudFoundryHealthEndpointWebExtension.java

@@ -17,13 +17,15 @@
 package org.springframework.boot.actuate.autoconfigure.cloudfoundry.servlet;
 
 import org.springframework.boot.actuate.autoconfigure.cloudfoundry.EndpointCloudFoundryExtension;
+import org.springframework.boot.actuate.endpoint.SecurityContext;
 import org.springframework.boot.actuate.endpoint.annotation.EndpointExtension;
 import org.springframework.boot.actuate.endpoint.annotation.ReadOperation;
+import org.springframework.boot.actuate.endpoint.annotation.Selector;
+import org.springframework.boot.actuate.endpoint.annotation.Selector.Match;
 import org.springframework.boot.actuate.endpoint.web.WebEndpointResponse;
-import org.springframework.boot.actuate.health.Health;
+import org.springframework.boot.actuate.health.HealthComponent;
 import org.springframework.boot.actuate.health.HealthEndpoint;
 import org.springframework.boot.actuate.health.HealthEndpointWebExtension;
-import org.springframework.boot.actuate.health.ShowDetails;
 
 /**
  * {@link EndpointExtension @EndpointExtension} for the {@link HealthEndpoint} that always
@@ -42,8 +44,13 @@ public CloudFoundryHealthEndpointWebExtension(HealthEndpointWebExtension delegat
 	}
 
 	@ReadOperation
-	public WebEndpointResponse<Health> getHealth() {
-		return this.delegate.getHealth(null, ShowDetails.ALWAYS);
+	public WebEndpointResponse<HealthComponent> health() {
+		return this.delegate.health(SecurityContext.NONE, true);
+	}
+
+	@ReadOperation
+	public WebEndpointResponse<HealthComponent> health(@Selector(match = Match.ALL_REMAINING) String... path) {
+		return this.delegate.health(SecurityContext.NONE, true, path);
 	}
 
 }

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

@@ -0,0 +1,73 @@
+/*
+ * 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.
+ * 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.health;
+
+import java.lang.reflect.Constructor;
+import java.util.Map;
+
+import org.springframework.beans.BeanUtils;
+import org.springframework.core.ResolvableType;
+import org.springframework.util.Assert;
+
+/**
+ * Base class for health contributor configurations that can combine source beans into a
+ * composite.
+ *
+ * @param <C> the contributor type
+ * @param <I> the health indicator type
+ * @param <B> the bean type
+ * @author Stephane Nicoll
+ * @author Phillip Webb
+ * @since 2.2.0
+ */
+public abstract class AbstractCompositeHealthContributorConfiguration<C, I extends C, B> {
+
+	private final Class<?> indicatorType;
+
+	private final Class<?> beanType;
+
+	AbstractCompositeHealthContributorConfiguration() {
+		ResolvableType type = ResolvableType.forClass(AbstractCompositeHealthContributorConfiguration.class,
+				getClass());
+		this.indicatorType = type.resolveGeneric(1);
+		this.beanType = type.resolveGeneric(2);
+
+	}
+
+	protected final C createContributor(Map<String, B> beans) {
+		Assert.notEmpty(beans, "Beans must not be empty");
+		if (beans.size() == 1) {
+			return createIndicator(beans.values().iterator().next());
+		}
+		return createComposite(beans);
+	}
+
+	protected abstract C createComposite(Map<String, B> beans);
+
+	@SuppressWarnings("unchecked")
+	protected I createIndicator(B bean) {
+		try {
+			Constructor<I> constructor = (Constructor<I>) this.indicatorType.getDeclaredConstructor(this.beanType);
+			return BeanUtils.instantiateClass(constructor, bean);
+		}
+		catch (Exception ex) {
+			throw new IllegalStateException(
+					"Unable to create health indicator " + this.indicatorType + " for bean type " + this.beanType, ex);
+		}
+	}
+
+}

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

@@ -0,0 +1,91 @@
+/*
+ * 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.
+ * 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.health;
+
+import java.util.Collection;
+
+import org.springframework.boot.actuate.autoconfigure.health.HealthEndpointProperties.ShowDetails;
+import org.springframework.boot.actuate.endpoint.SecurityContext;
+import org.springframework.boot.actuate.health.HealthEndpointSettings;
+import org.springframework.boot.actuate.health.HttpCodeStatusMapper;
+import org.springframework.boot.actuate.health.StatusAggregator;
+import org.springframework.util.CollectionUtils;
+
+/**
+ * Auto-configured {@link HealthEndpointSettings} backed by
+ * {@link HealthEndpointProperties}.
+ *
+ * @author Phillip Webb
+ * @author Andy Wilkinson
+ */
+class AutoConfiguredHealthEndpointSettings implements HealthEndpointSettings {
+
+	private final StatusAggregator statusAggregator;
+
+	private final HttpCodeStatusMapper httpCodeStatusMapper;
+
+	private final ShowDetails showDetails;
+
+	private final Collection<String> roles;
+
+	/**
+	 * Create a new {@link AutoConfiguredHealthEndpointSettings} instance.
+	 * @param statusAggregator the status aggregator to use
+	 * @param httpCodeStatusMapper the HTTP code status mapper to use
+	 * @param showDetails the show details setting
+	 * @param roles the roles to match
+	 */
+	AutoConfiguredHealthEndpointSettings(StatusAggregator statusAggregator, HttpCodeStatusMapper httpCodeStatusMapper,
+			ShowDetails showDetails, Collection<String> roles) {
+		this.statusAggregator = statusAggregator;
+		this.httpCodeStatusMapper = httpCodeStatusMapper;
+		this.showDetails = showDetails;
+		this.roles = roles;
+	}
+
+	@Override
+	public boolean includeDetails(SecurityContext securityContext) {
+		ShowDetails showDetails = this.showDetails;
+		switch (showDetails) {
+		case NEVER:
+			return false;
+		case ALWAYS:
+			return true;
+		case WHEN_AUTHORIZED:
+			return isAuthorized(securityContext);
+		}
+		throw new IllegalStateException("Unsupported ShowDetails value " + showDetails);
+	}
+
+	private boolean isAuthorized(SecurityContext securityContext) {
+		if (securityContext.getPrincipal() == null) {
+			return false;
+		}
+		return CollectionUtils.isEmpty(this.roles) || this.roles.stream().anyMatch(securityContext::isUserInRole);
+	}
+
+	@Override
+	public StatusAggregator getStatusAggregator() {
+		return this.statusAggregator;
+	}
+
+	@Override
+	public HttpCodeStatusMapper getHttpCodeStatusMapper() {
+		return this.httpCodeStatusMapper;
+	}
+
+}

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

@@ -0,0 +1,43 @@
+/*
+ * 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.
+ * 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.health;
+
+import java.util.Map;
+
+import org.springframework.boot.actuate.health.CompositeHealthContributor;
+import org.springframework.boot.actuate.health.HealthContributor;
+import org.springframework.boot.actuate.health.HealthIndicator;
+
+/**
+ * Base class for health contributor configurations that can combine source beans into a
+ * composite.
+ *
+ * @param <I> the health indicator type
+ * @param <B> the bean type
+ * @author Stephane Nicoll
+ * @author Phillip Webb
+ * @since 2.2.0
+ */
+public abstract class CompositeHealthContributorConfiguration<I extends HealthIndicator, B>
+		extends AbstractCompositeHealthContributorConfiguration<HealthContributor, I, B> {
+
+	@Override
+	protected final HealthContributor createComposite(Map<String, B> beans) {
+		return CompositeHealthContributor.fromMap(beans, this::createIndicator);
+	}
+
+}

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

@@ -34,7 +34,9 @@
  * @param <S> the bean source type
  * @author Stephane Nicoll
  * @since 2.0.0
+ * @deprecated since 2.0.0 in favor of {@link CompositeHealthContributorConfiguration}
  */
+@Deprecated
 public abstract class CompositeHealthIndicatorConfiguration<H extends HealthIndicator, S> {
 
 	@Autowired

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

@@ -0,0 +1,43 @@
+/*
+ * 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.
+ * 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.health;
+
+import java.util.Map;
+
+import org.springframework.boot.actuate.health.CompositeReactiveHealthContributor;
+import org.springframework.boot.actuate.health.ReactiveHealthContributor;
+import org.springframework.boot.actuate.health.ReactiveHealthIndicator;
+
+/**
+ * Base class for health contributor configurations that can combine source beans into a
+ * composite.
+ *
+ * @param <I> the health indicator type
+ * @param <B> the bean type
+ * @author Stephane Nicoll
+ * @author Phillip Webb
+ * @since 2.2.0
+ */
+public abstract class CompositeReactiveHealthContributorConfiguration<I extends ReactiveHealthIndicator, B>
+		extends AbstractCompositeHealthContributorConfiguration<ReactiveHealthContributor, I, B> {
+
+	@Override
+	protected final ReactiveHealthContributor createComposite(Map<String, B> beans) {
+		return CompositeReactiveHealthContributor.fromMap(beans, this::createIndicator);
+	}
+
+}

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

@@ -33,7 +33,10 @@
  * @param <S> the bean source type
  * @author Stephane Nicoll
  * @since 2.0.0
+ * @deprecated since 2.2.0 in favor of
+ * {@link CompositeReactiveHealthContributorConfiguration}
  */
+@Deprecated
 public abstract class CompositeReactiveHealthIndicatorConfiguration<H extends ReactiveHealthIndicator, S> {
 
 	@Autowired