Polish "Introduce HealthIndicatorRegistry"

See gh-4965

Co-authored-by: Andy Wilkinson <awilkinson@pivotal.io>

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

@@ -20,8 +20,10 @@ import java.util.Map;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.actuate.health.CompositeHealthIndicator;
+import org.springframework.boot.actuate.health.DefaultHealthIndicatorRegistry;
 import org.springframework.boot.actuate.health.HealthAggregator;
 import org.springframework.boot.actuate.health.HealthIndicator;
+import org.springframework.boot.actuate.health.HealthIndicatorRegistry;
 import org.springframework.core.ResolvableType;
 
 /**
@@ -42,11 +44,10 @@ public abstract class CompositeHealthIndicatorConfiguration<H extends HealthIndi
 		if (beans.size() == 1) {
 			return createHealthIndicator(beans.values().iterator().next());
 		}
-		CompositeHealthIndicator composite = new CompositeHealthIndicator(
-				this.healthAggregator);
-		beans.forEach((name, source) -> composite.addHealthIndicator(name,
-				createHealthIndicator(source)));
-		return composite;
+		HealthIndicatorRegistry registry = new DefaultHealthIndicatorRegistry();
+		beans.forEach(
+				(name, source) -> registry.register(name, createHealthIndicator(source)));
+		return new CompositeHealthIndicator(this.healthAggregator, registry);
 	}
 
 	@SuppressWarnings("unchecked")

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

@@ -16,13 +16,13 @@
 
 package org.springframework.boot.actuate.autoconfigure.health;
 
-import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.boot.actuate.autoconfigure.endpoint.condition.ConditionalOnEnabledEndpoint;
+import org.springframework.boot.actuate.health.CompositeHealthIndicator;
 import org.springframework.boot.actuate.health.HealthAggregator;
 import org.springframework.boot.actuate.health.HealthEndpoint;
 import org.springframework.boot.actuate.health.HealthIndicatorRegistry;
-import org.springframework.boot.actuate.health.OrderedHealthAggregator;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnSingleCandidate;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 
@@ -30,27 +30,18 @@ import org.springframework.context.annotation.Configuration;
  * Configuration for {@link HealthEndpoint}.
  *
  * @author Stephane Nicoll
- * @author Vedran Pavic
  */
 @Configuration
+@ConditionalOnSingleCandidate(HealthIndicatorRegistry.class)
 class HealthEndpointConfiguration {
 
-	private final HealthAggregator healthAggregator;
-
-	private final HealthIndicatorRegistry healthIndicatorRegistry;
-
-	HealthEndpointConfiguration(ObjectProvider<HealthAggregator> healthAggregator,
-			ObjectProvider<HealthIndicatorRegistry> healthIndicatorRegistry) {
-		this.healthAggregator = healthAggregator
-				.getIfAvailable(OrderedHealthAggregator::new);
-		this.healthIndicatorRegistry = healthIndicatorRegistry.getObject();
-	}
-
 	@Bean
 	@ConditionalOnMissingBean
 	@ConditionalOnEnabledEndpoint
-	public HealthEndpoint healthEndpoint() {
-		return new HealthEndpoint(this.healthAggregator, this.healthIndicatorRegistry);
+	public HealthEndpoint healthEndpoint(HealthAggregator healthAggregator,
+			HealthIndicatorRegistry registry) {
+		return new HealthEndpoint(
+				new CompositeHealthIndicator(healthAggregator, registry));
 	}
 
 }

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

@@ -16,11 +16,7 @@
 
 package org.springframework.boot.actuate.autoconfigure.health;
 
-import java.util.LinkedHashMap;
-import java.util.Map;
-
 import org.springframework.boot.actuate.health.ApplicationHealthIndicator;
-import org.springframework.boot.actuate.health.DefaultHealthIndicatorRegistry;
 import org.springframework.boot.actuate.health.HealthAggregator;
 import org.springframework.boot.actuate.health.HealthIndicator;
 import org.springframework.boot.actuate.health.HealthIndicatorRegistry;
@@ -32,7 +28,6 @@ import org.springframework.boot.context.properties.EnableConfigurationProperties
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.util.ClassUtils;
 
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for {@link HealthIndicator}s.
@@ -73,30 +68,7 @@ public class HealthIndicatorAutoConfiguration {
 	@ConditionalOnMissingBean(HealthIndicatorRegistry.class)
 	public HealthIndicatorRegistry healthIndicatorRegistry(
 			ApplicationContext applicationContext) {
-		HealthIndicatorRegistry registry = new DefaultHealthIndicatorRegistry();
-		Map<String, HealthIndicator> indicators = new LinkedHashMap<>();
-		indicators.putAll(applicationContext.getBeansOfType(HealthIndicator.class));
-		if (ClassUtils.isPresent("reactor.core.publisher.Flux", null)) {
-			new ReactiveHealthIndicators().get(applicationContext)
-					.forEach(indicators::putIfAbsent);
-		}
-		indicators.forEach(registry::register);
-		return registry;
-	}
-
-	private static class ReactiveHealthIndicators {
-
-		public Map<String, HealthIndicator> get(ApplicationContext applicationContext) {
-			Map<String, HealthIndicator> indicators = new LinkedHashMap<>();
-			applicationContext.getBeansOfType(ReactiveHealthIndicator.class)
-					.forEach((name, indicator) -> indicators.put(name, adapt(indicator)));
-			return indicators;
-		}
-
-		private HealthIndicator adapt(ReactiveHealthIndicator indicator) {
-			return () -> indicator.health().block();
-		}
-
+		return HealthIndicatorRegistryBeans.get(applicationContext);
 	}
 
 }

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

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2012-2018 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
+ *
+ *      http://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.LinkedHashMap;
+import java.util.Map;
+
+import org.springframework.boot.actuate.health.HealthIndicator;
+import org.springframework.boot.actuate.health.HealthIndicatorRegistry;
+import org.springframework.boot.actuate.health.HealthIndicatorRegistryFactory;
+import org.springframework.boot.actuate.health.ReactiveHealthIndicator;
+import org.springframework.context.ApplicationContext;
+import org.springframework.util.ClassUtils;
+
+/**
+ * Creates a {@link HealthIndicatorRegistry} from beans in the {@link ApplicationContext}.
+ *
+ * @author Phillip Webb
+ * @author Stephane Nicoll
+ */
+final class HealthIndicatorRegistryBeans {
+
+	private HealthIndicatorRegistryBeans() {
+	}
+
+	public static HealthIndicatorRegistry get(ApplicationContext applicationContext) {
+		Map<String, HealthIndicator> indicators = new LinkedHashMap<>();
+		indicators.putAll(applicationContext.getBeansOfType(HealthIndicator.class));
+		if (ClassUtils.isPresent("reactor.core.publisher.Flux", null)) {
+			new ReactiveHealthIndicators().get(applicationContext)
+					.forEach(indicators::putIfAbsent);
+		}
+		HealthIndicatorRegistryFactory factory = new HealthIndicatorRegistryFactory();
+		return factory.createHealthIndicatorRegistry(indicators);
+	}
+
+	private static class ReactiveHealthIndicators {
+
+		public Map<String, HealthIndicator> get(ApplicationContext applicationContext) {
+			Map<String, HealthIndicator> indicators = new LinkedHashMap<>();
+			applicationContext.getBeansOfType(ReactiveHealthIndicator.class)
+					.forEach((name, indicator) -> indicators.put(name, adapt(indicator)));
+			return indicators;
+		}
+
+		private HealthIndicator adapt(ReactiveHealthIndicator indicator) {
+			return () -> indicator.health().block();
+		}
+
+	}
+
+}

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/cloudfoundry/CloudFoundryWebEndpointDiscovererTests.java

@@ -34,9 +34,8 @@ import org.springframework.boot.actuate.endpoint.web.ExposableWebEndpoint;
 import org.springframework.boot.actuate.endpoint.web.PathMapper;
 import org.springframework.boot.actuate.endpoint.web.WebOperation;
 import org.springframework.boot.actuate.endpoint.web.annotation.EndpointWebExtension;
-import org.springframework.boot.actuate.health.HealthAggregator;
 import org.springframework.boot.actuate.health.HealthEndpoint;
-import org.springframework.boot.actuate.health.HealthIndicatorRegistry;
+import org.springframework.boot.actuate.health.HealthIndicator;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -110,8 +109,7 @@ public class CloudFoundryWebEndpointDiscovererTests {
 
 		@Bean
 		public HealthEndpoint healthEndpoint() {
-			return new HealthEndpoint(mock(HealthAggregator.class),
-					mock(HealthIndicatorRegistry.class));
+			return new HealthEndpoint(mock(HealthIndicator.class));
 		}
 
 		@Bean

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/endpoint/web/documentation/HealthEndpointDocumentationTests.java

@@ -23,10 +23,10 @@ import javax.sql.DataSource;
 
 import org.junit.Test;
 
-import org.springframework.boot.actuate.health.DefaultHealthIndicatorRegistry;
+import org.springframework.boot.actuate.health.CompositeHealthIndicator;
 import org.springframework.boot.actuate.health.HealthEndpoint;
 import org.springframework.boot.actuate.health.HealthIndicator;
-import org.springframework.boot.actuate.health.HealthIndicatorRegistry;
+import org.springframework.boot.actuate.health.HealthIndicatorRegistryFactory;
 import org.springframework.boot.actuate.health.OrderedHealthAggregator;
 import org.springframework.boot.actuate.jdbc.DataSourceHealthIndicator;
 import org.springframework.boot.actuate.system.DiskSpaceHealthIndicator;
@@ -73,9 +73,9 @@ public class HealthEndpointDocumentationTests extends MockMvcEndpointDocumentati
 
 		@Bean
 		public HealthEndpoint endpoint(Map<String, HealthIndicator> healthIndicators) {
-			HealthIndicatorRegistry registry = new DefaultHealthIndicatorRegistry();
-			healthIndicators.forEach(registry::register);
-			return new HealthEndpoint(new OrderedHealthAggregator(), registry);
+			return new HealthEndpoint(new CompositeHealthIndicator(
+					new OrderedHealthAggregator(), new HealthIndicatorRegistryFactory()
+							.createHealthIndicatorRegistry(healthIndicators)));
 		}
 
 		@Bean

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/integrationtest/JmxEndpointIntegrationTests.java

@@ -48,7 +48,8 @@ public class JmxEndpointIntegrationTests {
 	private final WebApplicationContextRunner contextRunner = new WebApplicationContextRunner()
 			.withConfiguration(AutoConfigurations.of(JmxAutoConfiguration.class,
 					EndpointAutoConfiguration.class, JmxEndpointAutoConfiguration.class,
-					HttpTraceAutoConfiguration.class, HealthIndicatorAutoConfiguration.class))
+					HealthIndicatorAutoConfiguration.class,
+					HttpTraceAutoConfiguration.class))
 			.withConfiguration(
 					AutoConfigurations.of(EndpointAutoConfigurationClasses.ALL));
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -19,8 +19,6 @@ package org.springframework.boot.actuate.health;
 import java.util.LinkedHashMap;
 import java.util.Map;
 
-import org.springframework.util.Assert;
-
 /**
  * {@link HealthIndicator} that returns health indications from all registered delegates.
  *
@@ -31,43 +29,71 @@ import org.springframework.util.Assert;
  */
 public class CompositeHealthIndicator implements HealthIndicator {
 
-	private final Map<String, HealthIndicator> indicators;
+	private final HealthIndicatorRegistry registry;
 
-	private final HealthAggregator healthAggregator;
+	private final HealthAggregator aggregator;
 
 	/**
 	 * Create a new {@link CompositeHealthIndicator}.
 	 * @param healthAggregator the health aggregator
+	 * @deprecated since 2.1.0 in favour of
+	 * {@link #CompositeHealthIndicator(HealthAggregator, HealthIndicatorRegistry)}
 	 */
+	@Deprecated
 	public CompositeHealthIndicator(HealthAggregator healthAggregator) {
-		this(healthAggregator, new LinkedHashMap<>());
+		this(healthAggregator, new DefaultHealthIndicatorRegistry());
 	}
 
 	/**
-	 * Create a new {@link CompositeHealthIndicator} from the specified indicators.
+	 * Create a new {@link CompositeHealthIndicator} from the specified
+	 * indicators.
 	 * @param healthAggregator the health aggregator
-	 * @param indicators a map of {@link HealthIndicator}s with the key being used as an
-	 * indicator name.
+	 * @param indicators a map of {@link HealthIndicator HealthIndicators} with
+	 * the key being used as an indicator name.
+	 * @deprecated since 2.1.0 in favour of
+	 * {@link #CompositeHealthIndicator(HealthAggregator, HealthIndicatorRegistry)}
 	 */
+	@Deprecated
 	public CompositeHealthIndicator(HealthAggregator healthAggregator,
 			Map<String, HealthIndicator> indicators) {
-		Assert.notNull(healthAggregator, "HealthAggregator must not be null");
-		Assert.notNull(indicators, "Indicators must not be null");
-		this.indicators = new LinkedHashMap<>(indicators);
-		this.healthAggregator = healthAggregator;
+		this(healthAggregator, new DefaultHealthIndicatorRegistry(indicators));
 	}
 
+	/**
+	 * Create a new {@link CompositeHealthIndicator} from the indicators in the
+	 * given {@code registry}.
+	 * @param healthAggregator the health aggregator
+	 * @param registry the registry of {@link HealthIndicator HealthIndicators}.
+	 */
+	public CompositeHealthIndicator(HealthAggregator healthAggregator,
+			HealthIndicatorRegistry registry) {
+		this.aggregator = healthAggregator;
+		this.registry = registry;
+	}
+
+	/**
+	 * Adds the given {@code healthIndicator}, associating it with the given
+	 * {@code name}.
+	 * @param name the name of the indicator
+	 * @param indicator the indicator
+	 * @throws IllegalStateException if an indicator with the given {@code name}
+	 * is already registered.
+	 * @deprecated since 2.1.0 in favour of
+	 * {@link HealthIndicatorRegistry#register(String, HealthIndicator)}
+	 */
+	@Deprecated
 	public void addHealthIndicator(String name, HealthIndicator indicator) {
-		this.indicators.put(name, indicator);
+		this.registry.register(name, indicator);
 	}
 
 	@Override
 	public Health health() {
 		Map<String, Health> healths = new LinkedHashMap<>();
-		for (Map.Entry<String, HealthIndicator> entry : this.indicators.entrySet()) {
+		for (Map.Entry<String, HealthIndicator> entry : this.registry.getAll()
+				.entrySet()) {
 			healths.put(entry.getKey(), entry.getValue().health());
 		}
-		return this.healthAggregator.aggregate(healths);
+		return this.aggregator.aggregate(healths);
 	}
 
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -26,20 +26,23 @@ import org.springframework.util.Assert;
  *
  * @author Stephane Nicoll
  * @since 2.0.0
+ * @deprecated since 2.1.0 in favor of
+ * {@link CompositeHealthIndicator#CompositeHealthIndicator(HealthAggregator, HealthIndicatorRegistry)}
  */
+@Deprecated
 public class CompositeHealthIndicatorFactory {
 
 	private final Function<String, String> healthIndicatorNameFactory;
 
+	public CompositeHealthIndicatorFactory() {
+		this(new HealthIndicatorNameFactory());
+	}
+
 	public CompositeHealthIndicatorFactory(
 			Function<String, String> healthIndicatorNameFactory) {
 		this.healthIndicatorNameFactory = healthIndicatorNameFactory;
 	}
 
-	public CompositeHealthIndicatorFactory() {
-		this(new HealthIndicatorNameFactory());
-	}
-
 	/**
 	 * Create a {@link CompositeHealthIndicator} based on the specified health indicators.
 	 * @param healthAggregator the {@link HealthAggregator}
@@ -52,13 +55,10 @@ public class CompositeHealthIndicatorFactory {
 			Map<String, HealthIndicator> healthIndicators) {
 		Assert.notNull(healthAggregator, "HealthAggregator must not be null");
 		Assert.notNull(healthIndicators, "HealthIndicators must not be null");
-		CompositeHealthIndicator healthIndicator = new CompositeHealthIndicator(
-				healthAggregator);
-		for (Map.Entry<String, HealthIndicator> entry : healthIndicators.entrySet()) {
-			String name = this.healthIndicatorNameFactory.apply(entry.getKey());
-			healthIndicator.addHealthIndicator(name, entry.getValue());
-		}
-		return healthIndicator;
+		HealthIndicatorRegistryFactory factory = new HealthIndicatorRegistryFactory(
+				this.healthIndicatorNameFactory);
+		return new CompositeHealthIndicator(
+				healthAggregator, factory.createHealthIndicatorRegistry(healthIndicators));
 	}
 
 }

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

@@ -17,7 +17,7 @@
 package org.springframework.boot.actuate.health;
 
 import java.util.Collections;
-import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.Map;
 
 import org.springframework.util.Assert;
@@ -26,42 +26,68 @@ import org.springframework.util.Assert;
  * Default implementation of {@link HealthIndicatorRegistry}.
  *
  * @author Vedran Pavic
+ * @author Stephane Nicoll
  * @since 2.1.0
  */
 public class DefaultHealthIndicatorRegistry implements HealthIndicatorRegistry {
 
-	private final Map<String, HealthIndicator> healthIndicators = new HashMap<>();
+	private final Object monitor = new Object();
+
+	private final Map<String, HealthIndicator> healthIndicators;
+
+	/**
+	 * Create a new {@link DefaultHealthIndicatorRegistry}.
+	 */
+	public DefaultHealthIndicatorRegistry() {
+		this(new LinkedHashMap<>());
+	}
+
+	/**
+	 * Create a new {@link DefaultHealthIndicatorRegistry} from the specified
+	 * indicators.
+	 * @param healthIndicators a map of {@link HealthIndicator}s with the key
+	 * being used as an indicator name.
+	 */
+	public DefaultHealthIndicatorRegistry(Map<String, HealthIndicator> healthIndicators) {
+		Assert.notNull(healthIndicators, "HealthIndicators must not be null");
+		this.healthIndicators = new LinkedHashMap<>(healthIndicators);
+	}
 
 	@Override
 	public void register(String name, HealthIndicator healthIndicator) {
 		Assert.notNull(healthIndicator, "HealthIndicator must not be null");
-		synchronized (this.healthIndicators) {
-			if (this.healthIndicators.get(name) != null) {
+		Assert.notNull(name, "Name must not be null");
+		synchronized (this.monitor) {
+			HealthIndicator existing = this.healthIndicators.putIfAbsent(name,
+					healthIndicator);
+			if (existing != null) {
 				throw new IllegalStateException(
 						"HealthIndicator with name '" + name + "' already registered");
 			}
-			this.healthIndicators.put(name, healthIndicator);
 		}
 	}
 
 	@Override
 	public HealthIndicator unregister(String name) {
-		synchronized (this.healthIndicators) {
+		Assert.notNull(name, "Name must not be null");
+		synchronized (this.monitor) {
 			return this.healthIndicators.remove(name);
 		}
 	}
 
 	@Override
 	public HealthIndicator get(String name) {
-		synchronized (this.healthIndicators) {
+		Assert.notNull(name, "Name must not be null");
+		synchronized (this.monitor) {
 			return this.healthIndicators.get(name);
 		}
 	}
 
 	@Override
 	public Map<String, HealthIndicator> getAll() {
-		synchronized (this.healthIndicators) {
-			return Collections.unmodifiableMap(new HashMap<>(this.healthIndicators));
+		synchronized (this.monitor) {
+			return Collections
+					.unmodifiableMap(new LinkedHashMap<>(this.healthIndicators));
 		}
 	}
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -19,8 +19,7 @@ package org.springframework.boot.actuate.health;
 import java.util.Map;
 
 /**
- * Strategy interface used by {@link CompositeHealthIndicator} to aggregate {@link Health}
- * instances into a final one.
+ * Strategy interface used to aggregate {@link Health} instances into a final one.
  * <p>
  * This is especially useful to combine subsystem states expressed through
  * {@link Health#getStatus()} into one state for the entire system. The default

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

@@ -26,35 +26,26 @@ import org.springframework.util.Assert;
  * @author Dave Syer
  * @author Christian Dupuis
  * @author Andy Wilkinson
- * @author Vedran Pavic
  * @since 2.0.0
  */
 @Endpoint(id = "health")
 public class HealthEndpoint {
 
-	private final HealthAggregator healthAggregator;
-
-	private final HealthIndicatorRegistry healthIndicatorRegistry;
+	private final HealthIndicator healthIndicator;
 
 	/**
-	 * Create a new {@link HealthEndpoint} instance.
-	 * @param healthAggregator the health aggregator
-	 * @param healthIndicatorRegistry the health indicator registry
+	 * Create a new {@link HealthEndpoint} instance that will use the given
+	 * {@code healthIndicator} to generate its response.
+	 * @param healthIndicator the health indicator
 	 */
-	public HealthEndpoint(HealthAggregator healthAggregator,
-			HealthIndicatorRegistry healthIndicatorRegistry) {
-		Assert.notNull(healthAggregator, "healthAggregator must not be null");
-		Assert.notNull(healthIndicatorRegistry, "healthIndicatorRegistry must not be null");
-		this.healthAggregator = healthAggregator;
-		this.healthIndicatorRegistry = healthIndicatorRegistry;
+	public HealthEndpoint(HealthIndicator healthIndicator) {
+		Assert.notNull(healthIndicator, "HealthIndicator must not be null");
+		this.healthIndicator = healthIndicator;
 	}
 
 	@ReadOperation
 	public Health health() {
-		CompositeHealthIndicatorFactory factory = new CompositeHealthIndicatorFactory();
-		CompositeHealthIndicator healthIndicator = factory.createHealthIndicator(
-				this.healthAggregator, this.healthIndicatorRegistry.getAll());
-		return healthIndicator.health();
+		return this.healthIndicator.health();
 	}
 
 }

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

@@ -19,46 +19,48 @@ package org.springframework.boot.actuate.health;
 import java.util.Map;
 
 /**
- * A registry of {@link HealthIndicator}s.
+ * A registry of {@link HealthIndicator HealthIndicators}.
  * <p>
  * Implementations <strong>must</strong> be thread-safe.
  *
  * @author Andy Wilkinson
  * @author Vedran Pavic
+ * @author Stephane Nicoll
  * @since 2.1.0
  */
 public interface HealthIndicatorRegistry {
 
 	/**
-	 * Registers the given {@code healthIndicator}, associating it with the given
-	 * {@code name}.
+	 * Registers the given {@code healthIndicator}, associating it with the
+	 * given {@code name}.
 	 * @param name the name of the indicator
 	 * @param healthIndicator the indicator
-	 * @throws IllegalStateException if an indicator with the given {@code name} is
-	 * already registered.
+	 * @throws IllegalStateException if an indicator with the given {@code name}
+	 * is already registered.
 	 */
 	void register(String name, HealthIndicator healthIndicator);
 
 	/**
-	 * Unregisters the {@code HealthIndicator} previously registered with the given
-	 * {@code name}.
+	 * Unregisters the {@code HealthIndicator} previously registered with the
+	 * given {@code name}.
 	 * @param name the name of the indicator
-	 * @return the unregistered indicator, or {@code null} if no indicator was found in
-	 * the registry for the given {@code name}.
+	 * @return the unregistered indicator, or {@code null} if no indicator was
+	 * found in the registry for the given {@code name}.
 	 */
 	HealthIndicator unregister(String name);
 
 	/**
 	 * Returns the health indicator registered with the given {@code name}.
 	 * @param name the name of the indicator
-	 * @return the health indicator, or {@code null} if no indicator was registered with
-	 * the given {@code name}.
+	 * @return the health indicator, or {@code null} if no indicator was
+	 * registered with the given {@code name}.
 	 */
 	HealthIndicator get(String name);
 
 	/**
-	 * Returns a snapshot of the registered health indicators and their names. The
-	 * contents of the map do not reflect subsequent changes to the registry.
+	 * Returns a snapshot of the registered health indicators and their names.
+	 * The contents of the map do not reflect subsequent changes to the
+	 * registry.
 	 * @return the snapshot of registered health indicators
 	 */
 	Map<String, HealthIndicator> getAll();

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

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2012-2018 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
+ *
+ *      http://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.Map;
+import java.util.function.Function;
+
+import org.springframework.util.Assert;
+
+/**
+ * Factory to create a {@link HealthIndicatorRegistry}.
+ *
+ * @author Stephane Nicoll
+ * @since 2.1.0
+ */
+public class HealthIndicatorRegistryFactory {
+
+	private final Function<String, String> healthIndicatorNameFactory;
+
+	public HealthIndicatorRegistryFactory(
+			Function<String, String> healthIndicatorNameFactory) {
+		this.healthIndicatorNameFactory = healthIndicatorNameFactory;
+	}
+
+	public HealthIndicatorRegistryFactory() {
+		this(new HealthIndicatorNameFactory());
+	}
+
+	/**
+	 * Create a {@link HealthIndicatorRegistry} based on the specified health
+	 * indicators.
+	 * @param healthIndicators the {@link HealthIndicator} instances mapped by
+	 * name
+	 * @return a {@link HealthIndicator} that delegates to the specified
+	 * {@code healthIndicators}.
+	 */
+	public HealthIndicatorRegistry createHealthIndicatorRegistry(
+			Map<String, HealthIndicator> healthIndicators) {
+		Assert.notNull(healthIndicators, "HealthIndicators must not be null");
+		return initialize(new DefaultHealthIndicatorRegistry(), healthIndicators);
+	}
+
+	protected <T extends HealthIndicatorRegistry> T initialize(T registry,
+			Map<String, HealthIndicator> healthIndicators) {
+		for (Map.Entry<String, HealthIndicator> entry : healthIndicators.entrySet()) {
+			String name = this.healthIndicatorNameFactory.apply(entry.getKey());
+			registry.register(name, entry.getValue());
+		}
+		return registry;
+	}
+
+}

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/health/CompositeHealthIndicatorFactoryTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -30,6 +30,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  * @author Christian Dupuis
  * @author Andy Wilkinson
  */
+@Deprecated
 public class CompositeHealthIndicatorFactoryTests {
 
 	@Test

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/health/CompositeHealthIndicatorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -16,6 +16,7 @@
 
 package org.springframework.boot.actuate.health;
 
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -45,9 +46,6 @@ public class CompositeHealthIndicatorTests {
 	@Mock
 	private HealthIndicator two;
 
-	@Mock
-	private HealthIndicator three;
-
 	@Before
 	public void setup() {
 		MockitoAnnotations.initMocks(this);
@@ -55,8 +53,6 @@ public class CompositeHealthIndicatorTests {
 				.willReturn(new Health.Builder().unknown().withDetail("1", "1").build());
 		given(this.two.health())
 				.willReturn(new Health.Builder().unknown().withDetail("2", "2").build());
-		given(this.three.health())
-				.willReturn(new Health.Builder().unknown().withDetail("3", "3").build());
 
 		this.healthAggregator = new OrderedHealthAggregator();
 	}
@@ -67,7 +63,7 @@ public class CompositeHealthIndicatorTests {
 		indicators.put("one", this.one);
 		indicators.put("two", this.two);
 		CompositeHealthIndicator composite = new CompositeHealthIndicator(
-				this.healthAggregator, indicators);
+				this.healthAggregator, new DefaultHealthIndicatorRegistry(indicators));
 		Health result = composite.health();
 		assertThat(result.getDetails()).hasSize(2);
 		assertThat(result.getDetails()).containsEntry("one",
@@ -76,48 +72,16 @@ public class CompositeHealthIndicatorTests {
 				new Health.Builder().unknown().withDetail("2", "2").build());
 	}
 
-	@Test
-	public void createWithIndicatorsAndAdd() {
-		Map<String, HealthIndicator> indicators = new HashMap<>();
-		indicators.put("one", this.one);
-		indicators.put("two", this.two);
-		CompositeHealthIndicator composite = new CompositeHealthIndicator(
-				this.healthAggregator, indicators);
-		composite.addHealthIndicator("three", this.three);
-		Health result = composite.health();
-		assertThat(result.getDetails()).hasSize(3);
-		assertThat(result.getDetails()).containsEntry("one",
-				new Health.Builder().unknown().withDetail("1", "1").build());
-		assertThat(result.getDetails()).containsEntry("two",
-				new Health.Builder().unknown().withDetail("2", "2").build());
-		assertThat(result.getDetails()).containsEntry("three",
-				new Health.Builder().unknown().withDetail("3", "3").build());
-	}
-
-	@Test
-	public void createWithoutAndAdd() {
-		CompositeHealthIndicator composite = new CompositeHealthIndicator(
-				this.healthAggregator);
-		composite.addHealthIndicator("one", this.one);
-		composite.addHealthIndicator("two", this.two);
-		Health result = composite.health();
-		assertThat(result.getDetails().size()).isEqualTo(2);
-		assertThat(result.getDetails()).containsEntry("one",
-				new Health.Builder().unknown().withDetail("1", "1").build());
-		assertThat(result.getDetails()).containsEntry("two",
-				new Health.Builder().unknown().withDetail("2", "2").build());
-	}
-
 	@Test
 	public void testSerialization() throws Exception {
 		Map<String, HealthIndicator> indicators = new HashMap<>();
 		indicators.put("db1", this.one);
 		indicators.put("db2", this.two);
 		CompositeHealthIndicator innerComposite = new CompositeHealthIndicator(
-				this.healthAggregator, indicators);
+				this.healthAggregator, new DefaultHealthIndicatorRegistry(indicators));
 		CompositeHealthIndicator composite = new CompositeHealthIndicator(
-				this.healthAggregator);
-		composite.addHealthIndicator("db", innerComposite);
+				this.healthAggregator, new DefaultHealthIndicatorRegistry(
+						Collections.singletonMap("db", innerComposite)));
 		Health result = composite.health();
 		ObjectMapper mapper = new ObjectMapper();
 		assertThat(mapper.writeValueAsString(result)).isEqualTo(

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/health/DefaultHealthIndicatorRegistryTests.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.actuate.health;
 
+import java.util.Map;
+
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
@@ -29,8 +31,9 @@ import static org.mockito.Mockito.mock;
  * Tests for {@link DefaultHealthIndicatorRegistry}.
  *
  * @author Vedran Pavic
+ * @author Stephane Nicoll
  */
-public class DefaultHealthIndicatorRegistryTest {
+public class DefaultHealthIndicatorRegistryTests {
 
 	@Rule
 	public ExpectedException thrown = ExpectedException.none();
@@ -43,9 +46,10 @@ public class DefaultHealthIndicatorRegistryTest {
 
 	@Before
 	public void setUp() {
-		given(this.one.health()).willReturn(new Health.Builder().up().build());
-		given(this.two.health()).willReturn(new Health.Builder().unknown().build());
-
+		given(this.one.health())
+				.willReturn(new Health.Builder().unknown().withDetail("1", "1").build());
+		given(this.two.health())
+				.willReturn(new Health.Builder().unknown().withDetail("2", "2").build());
 		this.registry = new DefaultHealthIndicatorRegistry();
 	}
 
@@ -60,9 +64,9 @@ public class DefaultHealthIndicatorRegistryTest {
 
 	@Test
 	public void registerAlreadyUsedName() {
+		this.registry.register("one", this.one);
 		this.thrown.expect(IllegalStateException.class);
 		this.thrown.expectMessage("HealthIndicator with name 'one' already registered");
-		this.registry.register("one", this.one);
 		this.registry.register("one", this.two);
 	}
 
@@ -77,7 +81,7 @@ public class DefaultHealthIndicatorRegistryTest {
 	}
 
 	@Test
-	public void unregisterNotKnown() {
+	public void unregisterUnknown() {
 		this.registry.register("one", this.one);
 		assertThat(this.registry.getAll()).hasSize(1);
 		HealthIndicator two = this.registry.unregister("two");
@@ -85,4 +89,22 @@ public class DefaultHealthIndicatorRegistryTest {
 		assertThat(this.registry.getAll()).hasSize(1);
 	}
 
+	@Test
+	public void getAllIsASnapshot() {
+		this.registry.register("one", this.one);
+		Map<String, HealthIndicator> snapshot = this.registry.getAll();
+		assertThat(snapshot).containsOnlyKeys("one");
+		this.registry.register("two", this.two);
+		assertThat(snapshot).containsOnlyKeys("one");
+	}
+
+	@Test
+	public void getAllIsImmutable() {
+		this.registry.register("one", this.one);
+		Map<String, HealthIndicator> snapshot = this.registry.getAll();
+
+		this.thrown.expect(UnsupportedOperationException.class);
+		snapshot.clear();
+	}
+
 }

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/health/HealthEndpointTests.java

@@ -30,7 +30,6 @@ import static org.assertj.core.api.Assertions.entry;
  * @author Phillip Webb
  * @author Christian Dupuis
  * @author Andy Wilkinson
- * @author Vedran Pavic
  */
 public class HealthEndpointTests {
 
@@ -41,8 +40,8 @@ public class HealthEndpointTests {
 				.withDetail("first", "1").build());
 		healthIndicators.put("upAgain", () -> new Health.Builder().status(Status.UP)
 				.withDetail("second", "2").build());
-		HealthEndpoint endpoint = new HealthEndpoint(new OrderedHealthAggregator(),
-				createHealthIndicatorRegistry(healthIndicators));
+		HealthEndpoint endpoint = new HealthEndpoint(
+				createHealthIndicator(healthIndicators));
 		Health health = endpoint.health();
 		assertThat(health.getStatus()).isEqualTo(Status.UP);
 		assertThat(health.getDetails()).containsOnlyKeys("up", "upAgain");
@@ -52,11 +51,10 @@ public class HealthEndpointTests {
 		assertThat(upAgainHealth.getDetails()).containsOnly(entry("second", "2"));
 	}
 
-	private HealthIndicatorRegistry createHealthIndicatorRegistry(
+	private HealthIndicator createHealthIndicator(
 			Map<String, HealthIndicator> healthIndicators) {
-		HealthIndicatorRegistry registry = new DefaultHealthIndicatorRegistry();
-		healthIndicators.forEach(registry::register);
-		return registry;
+		return new CompositeHealthIndicator(new OrderedHealthAggregator(),
+				new DefaultHealthIndicatorRegistry(healthIndicators));
 	}
 
 }

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/health/HealthEndpointWebIntegrationTests.java

@@ -35,7 +35,6 @@ import org.springframework.test.web.reactive.server.WebTestClient;
  * exposed by Jersey, Spring MVC, and WebFlux.
  *
  * @author Andy Wilkinson
- * @author Vedran Pavic
  */
 @RunWith(WebEndpointRunners.class)
 public class HealthEndpointWebIntegrationTests {
@@ -53,23 +52,48 @@ public class HealthEndpointWebIntegrationTests {
 
 	@Test
 	public void whenHealthIsDown503ResponseIsReturned() {
-		context.getBean("alphaHealthIndicator", TestHealthIndicator.class)
-				.setHealth(Health.down().build());
-		client.get().uri("/actuator/health").exchange().expectStatus()
-				.isEqualTo(HttpStatus.SERVICE_UNAVAILABLE).expectBody().jsonPath("status")
-				.isEqualTo("DOWN").jsonPath("details.alpha.status").isEqualTo("DOWN")
-				.jsonPath("details.bravo.status").isEqualTo("UP");
+		HealthIndicatorRegistry registry = context.getBean(HealthIndicatorRegistry.class);
+		registry.register("charlie", () -> Health.down().build());
+		try {
+			client.get().uri("/actuator/health").exchange().expectStatus()
+					.isEqualTo(HttpStatus.SERVICE_UNAVAILABLE).expectBody().jsonPath("status")
+					.isEqualTo("DOWN").jsonPath("details.alpha.status").isEqualTo("UP")
+					.jsonPath("details.bravo.status").isEqualTo("UP")
+					.jsonPath("details.charlie.status").isEqualTo("DOWN");
+		}
+		finally {
+			registry.unregister("charlie");
+		}
+	}
+
+	@Test
+	public void whenHealthIndicatorIsRemovedResponseIsAltered() {
+		HealthIndicatorRegistry registry = context.getBean(HealthIndicatorRegistry.class);
+		HealthIndicator bravo = registry.unregister("bravo");
+		try {
+			client.get().uri("/actuator/health").exchange().expectStatus().isOk().expectBody()
+					.jsonPath("status").isEqualTo("UP").jsonPath("details.alpha.status")
+					.isEqualTo("UP").jsonPath("details.bravo.status").doesNotExist();
+		}
+		finally {
+			registry.register("bravo", bravo);
+		}
 	}
 
 	@Configuration
 	public static class TestConfiguration {
 
 		@Bean
-		public HealthEndpoint healthEndpoint(
+		public HealthIndicatorRegistry healthIndicatorFactory(
 				Map<String, HealthIndicator> healthIndicators) {
-			HealthIndicatorRegistry registry = new DefaultHealthIndicatorRegistry();
-			healthIndicators.forEach(registry::register);
-			return new HealthEndpoint(new OrderedHealthAggregator(), registry);
+			return new HealthIndicatorRegistryFactory()
+					.createHealthIndicatorRegistry(healthIndicators);
+		}
+
+		@Bean
+		public HealthEndpoint healthEndpoint(HealthIndicatorRegistry registry) {
+			return new HealthEndpoint(new CompositeHealthIndicator(
+					new OrderedHealthAggregator(), registry));
 		}
 
 		@Bean
@@ -82,30 +106,13 @@ public class HealthEndpointWebIntegrationTests {
 		}
 
 		@Bean
-		public TestHealthIndicator alphaHealthIndicator() {
-			return new TestHealthIndicator();
+		public HealthIndicator alphaHealthIndicator() {
+			return () -> Health.up().build();
 		}
 
 		@Bean
-		public TestHealthIndicator bravoHealthIndicator() {
-			return new TestHealthIndicator();
-		}
-
-	}
-
-	private static class TestHealthIndicator implements HealthIndicator {
-
-		private Health health = Health.up().build();
-
-		@Override
-		public Health health() {
-			Health result = this.health;
-			this.health = Health.up().build();
-			return result;
-		}
-
-		void setHealth(Health health) {
-			this.health = health;
+		public HealthIndicator bravoHealthIndicator() {
+			return () -> Health.up().build();
 		}
 
 	}

spring-boot-project/spring-boot-docs/src/main/asciidoc/production-ready-features.adoc

@@ -727,9 +727,9 @@ unauthenticated users.
 
 Health information is collected from all
 {sc-spring-boot-actuator}/health/HealthIndicator.{sc-ext}[`HealthIndicator`] instances
-registered with {sc-spring-boot-actuator}/health/HealthIndicatorRegistry.{sc-ext}[`HealthIndicatorRegistry`].
-Spring Boot includes a number of auto-configured `HealthIndicators` and you can also write
-your own. By default, the final system state is
+registered with {sc-spring-boot-actuator}/health/HealthIndicatorRegistry.{sc-ext}[
+`HealthIndicatorRegistry`]. Spring Boot includes a number of auto-configured
+`HealthIndicators` and you can also write your own. By default, the final system state is
 derived by the `HealthAggregator` which sorts the statuses from each `HealthIndicator`
 based on an ordered list of statuses. The first status in the sorted list is used as the
 overall health status. If no `HealthIndicator` returns a status that is known to the
@@ -820,7 +820,8 @@ NOTE: The identifier for a given `HealthIndicator` is the name of the bean witho
 is available in an entry named `my`.
 
 Additionally, you can register (and unregister) `HealthIndicator` instances in runtime
-using {sc-spring-boot-actuator}/health/HealthIndicatorRegistry.{sc-ext}[`HealthIndicatorRegistry`].
+using {sc-spring-boot-actuator}/health/HealthIndicatorRegistry.{sc-ext}[
+`HealthIndicatorRegistry`].
 
 In addition to Spring Boot's predefined
 {sc-spring-boot-actuator}/health/Status.{sc-ext}[`Status`] types, it is also possible for