Add BootstrapRegisty support for config data

Expose the `BootstrapRegisty` to both `ConfigDataLocationResolver` and
`ConfigDataLoader` implementations. The registry is exposed via the
context interfaces and may be used to reuse instances that are expensive
to create. It may also be used to ultimately register beans with the
`ApplicationContext`.

Closes gh-22956

Author: philwebb

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/context/ConfigDataApplicationContextInitializer.java

@@ -18,6 +18,7 @@
 
 import org.springframework.boot.context.config.ConfigData;
 import org.springframework.boot.context.config.ConfigDataEnvironmentPostProcessor;
+import org.springframework.boot.env.DefaultBootstrapRegisty;
 import org.springframework.boot.env.DefaultPropertiesPropertySource;
 import org.springframework.boot.env.RandomValuePropertySource;
 import org.springframework.context.ApplicationContextInitializer;
@@ -41,7 +42,9 @@ public class ConfigDataApplicationContextInitializer
 	public void initialize(ConfigurableApplicationContext applicationContext) {
 		ConfigurableEnvironment environment = applicationContext.getEnvironment();
 		RandomValuePropertySource.addToEnvironment(environment);
-		ConfigDataEnvironmentPostProcessor.applyTo(environment, applicationContext);
+		DefaultBootstrapRegisty bootstrapRegistry = new DefaultBootstrapRegisty();
+		ConfigDataEnvironmentPostProcessor.applyTo(environment, applicationContext, bootstrapRegistry);
+		bootstrapRegistry.applicationContextPrepared(applicationContext);
 		DefaultPropertiesPropertySource.moveToEnd(environment);
 	}
 

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataEnvironment.java

@@ -25,6 +25,7 @@
 import org.springframework.boot.context.config.ConfigDataEnvironmentContributors.BinderOption;
 import org.springframework.boot.context.properties.bind.BindException;
 import org.springframework.boot.context.properties.bind.Binder;
+import org.springframework.boot.env.BootstrapRegistry;
 import org.springframework.boot.env.DefaultPropertiesPropertySource;
 import org.springframework.boot.logging.DeferredLogFactory;
 import org.springframework.core.env.ConfigurableEnvironment;
@@ -77,6 +78,8 @@ class ConfigDataEnvironment {
 
 	private final Log logger;
 
+	private final BootstrapRegistry bootstrapRegistry;
+
 	private final ConfigurableEnvironment environment;
 
 	private final ConfigDataLocationResolvers resolvers;
@@ -90,16 +93,18 @@ class ConfigDataEnvironment {
 	/**
 	 * Create a new {@link ConfigDataEnvironment} instance.
 	 * @param logFactory the deferred log factory
+	 * @param bootstrapRegistry the bootstrap registry
 	 * @param environment the Spring {@link Environment}.
 	 * @param resourceLoader {@link ResourceLoader} to load resource locations
 	 * @param additionalProfiles any additional profiles to activate
 	 */
-	ConfigDataEnvironment(DeferredLogFactory logFactory, ConfigurableEnvironment environment,
-			ResourceLoader resourceLoader, Collection<String> additionalProfiles) {
+	ConfigDataEnvironment(DeferredLogFactory logFactory, BootstrapRegistry bootstrapRegistry,
+			ConfigurableEnvironment environment, ResourceLoader resourceLoader, Collection<String> additionalProfiles) {
 		Binder binder = Binder.get(environment);
 		UseLegacyConfigProcessingException.throwIfRequested(binder);
 		this.logFactory = logFactory;
 		this.logger = logFactory.getLog(getClass());
+		this.bootstrapRegistry = bootstrapRegistry;
 		this.environment = environment;
 		this.resolvers = createConfigDataLocationResolvers(logFactory, binder, resourceLoader);
 		this.additionalProfiles = additionalProfiles;
@@ -132,7 +137,7 @@ private ConfigDataEnvironmentContributors createContributors(Binder binder) {
 			this.logger.trace("Creating wrapped config data contributor for default property source");
 			contributors.add(ConfigDataEnvironmentContributor.ofExisting(defaultPropertySource));
 		}
-		return new ConfigDataEnvironmentContributors(this.logFactory, contributors);
+		return new ConfigDataEnvironmentContributors(this.logFactory, this.bootstrapRegistry, contributors);
 	}
 
 	ConfigDataEnvironmentContributors getContributors() {

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataEnvironmentContributors.java

@@ -36,6 +36,7 @@
 import org.springframework.boot.context.properties.bind.PlaceholdersResolver;
 import org.springframework.boot.context.properties.source.ConfigurationPropertyName;
 import org.springframework.boot.context.properties.source.ConfigurationPropertySource;
+import org.springframework.boot.env.BootstrapRegistry;
 import org.springframework.boot.logging.DeferredLogFactory;
 import org.springframework.core.log.LogMessage;
 import org.springframework.util.ObjectUtils;
@@ -53,19 +54,25 @@ class ConfigDataEnvironmentContributors implements Iterable<ConfigDataEnvironmen
 
 	private final ConfigDataEnvironmentContributor root;
 
+	private final BootstrapRegistry bootstrapRegistry;
+
 	/**
 	 * Create a new {@link ConfigDataEnvironmentContributors} instance.
 	 * @param logFactory the log factory
+	 * @param bootstrapRegistry the bootstrap registry
 	 * @param contributors the initial set of contributors
 	 */
-	ConfigDataEnvironmentContributors(DeferredLogFactory logFactory,
+	ConfigDataEnvironmentContributors(DeferredLogFactory logFactory, BootstrapRegistry bootstrapRegistry,
 			List<ConfigDataEnvironmentContributor> contributors) {
 		this.logger = logFactory.getLog(getClass());
+		this.bootstrapRegistry = bootstrapRegistry;
 		this.root = ConfigDataEnvironmentContributor.of(contributors);
 	}
 
-	private ConfigDataEnvironmentContributors(Log logger, ConfigDataEnvironmentContributor root) {
+	private ConfigDataEnvironmentContributors(Log logger, BootstrapRegistry bootstrapRegistry,
+			ConfigDataEnvironmentContributor root) {
 		this.logger = logger;
+		this.bootstrapRegistry = bootstrapRegistry;
 		this.root = root;
 	}
 
@@ -91,22 +98,27 @@ ConfigDataEnvironmentContributors withProcessedImports(ConfigDataImporter import
 				this.logger.trace(LogMessage.format("Processed imports for of %d contributors", processedCount));
 				return result;
 			}
-			ConfigDataLocationResolverContext locationResolverContext = new ContributorLocationResolverContext(result,
-					unprocessed, activationContext);
+			ConfigDataLocationResolverContext locationResolverContext = new ContributorConfigDataLocationResolverContext(
+					result, unprocessed, activationContext);
+			ConfigDataLoaderContext loaderContext = new ContributorDataLoaderContext(this);
 			List<String> imports = unprocessed.getImports();
 			this.logger.trace(LogMessage.format("Processing imports %s", imports));
 			Map<ConfigDataLocation, ConfigData> imported = importer.resolveAndLoad(activationContext,
-					locationResolverContext, imports);
+					locationResolverContext, loaderContext, imports);
 			this.logger.trace(LogMessage.of(() -> imported.isEmpty() ? "Nothing imported" : "Imported "
 					+ imported.size() + " location " + ((imported.size() != 1) ? "s" : "") + imported.keySet()));
 			ConfigDataEnvironmentContributor processed = unprocessed.withChildren(importPhase,
 					asContributors(activationContext, imported));
-			result = new ConfigDataEnvironmentContributors(this.logger,
+			result = new ConfigDataEnvironmentContributors(this.logger, this.bootstrapRegistry,
 					result.getRoot().withReplacement(unprocessed, processed));
 			processedCount++;
 		}
 	}
 
+	protected final BootstrapRegistry getBootstrapRegistry() {
+		return this.bootstrapRegistry;
+	}
+
 	private ConfigDataEnvironmentContributor getFirstUnprocessed(ConfigDataEnvironmentContributors contributors,
 			ConfigDataActivationContext activationContext, ImportPhase importPhase) {
 		for (ConfigDataEnvironmentContributor contributor : contributors.getRoot()) {
@@ -177,10 +189,27 @@ public Iterator<ConfigDataEnvironmentContributor> iterator() {
 	}
 
 	/**
-	 * {@link ConfigDataLocationResolverContext} backed by a
-	 * {@link ConfigDataEnvironmentContributor}.
+	 * {@link ConfigDataLocationResolverContext} for a contributor.
 	 */
-	private static class ContributorLocationResolverContext implements ConfigDataLocationResolverContext {
+	private static class ContributorDataLoaderContext implements ConfigDataLoaderContext {
+
+		private final ConfigDataEnvironmentContributors contributors;
+
+		ContributorDataLoaderContext(ConfigDataEnvironmentContributors contributors) {
+			this.contributors = contributors;
+		}
+
+		@Override
+		public BootstrapRegistry getBootstrapRegistry() {
+			return this.contributors.getBootstrapRegistry();
+		}
+
+	}
+
+	/**
+	 * {@link ConfigDataLocationResolverContext} for a contributor.
+	 */
+	private static class ContributorConfigDataLocationResolverContext implements ConfigDataLocationResolverContext {
 
 		private final ConfigDataEnvironmentContributors contributors;
 
@@ -190,7 +219,7 @@ private static class ContributorLocationResolverContext implements ConfigDataLoc
 
 		private volatile Binder binder;
 
-		ContributorLocationResolverContext(ConfigDataEnvironmentContributors contributors,
+		ContributorConfigDataLocationResolverContext(ConfigDataEnvironmentContributors contributors,
 				ConfigDataEnvironmentContributor contributor, ConfigDataActivationContext activationContext) {
 			this.contributors = contributors;
 			this.contributor = contributor;
@@ -212,6 +241,11 @@ public ConfigDataLocation getParent() {
 			return this.contributor.getLocation();
 		}
 
+		@Override
+		public BootstrapRegistry getBootstrapRegistry() {
+			return this.contributors.getBootstrapRegistry();
+		}
+
 	}
 
 	private class InactiveSourceChecker implements BindHandler {

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataEnvironmentPostProcessor.java

@@ -24,6 +24,8 @@
 import org.apache.commons.logging.Log;
 
 import org.springframework.boot.SpringApplication;
+import org.springframework.boot.env.BootstrapRegistry;
+import org.springframework.boot.env.DefaultBootstrapRegisty;
 import org.springframework.boot.env.EnvironmentPostProcessor;
 import org.springframework.boot.logging.DeferredLogFactory;
 import org.springframework.core.Ordered;
@@ -52,9 +54,12 @@ public class ConfigDataEnvironmentPostProcessor implements EnvironmentPostProces
 
 	private final Log logger;
 
-	public ConfigDataEnvironmentPostProcessor(DeferredLogFactory logFactory) {
+	private final BootstrapRegistry bootstrapRegistry;
+
+	public ConfigDataEnvironmentPostProcessor(DeferredLogFactory logFactory, BootstrapRegistry bootstrapRegistry) {
 		this.logFactory = logFactory;
 		this.logger = logFactory.getLog(getClass());
+		this.bootstrapRegistry = bootstrapRegistry;
 	}
 
 	@Override
@@ -83,7 +88,8 @@ void postProcessEnvironment(ConfigurableEnvironment environment, ResourceLoader
 
 	ConfigDataEnvironment getConfigDataEnvironment(ConfigurableEnvironment environment, ResourceLoader resourceLoader,
 			Collection<String> additionalProfiles) {
-		return new ConfigDataEnvironment(this.logFactory, environment, resourceLoader, additionalProfiles);
+		return new ConfigDataEnvironment(this.logFactory, this.bootstrapRegistry, environment, resourceLoader,
+				additionalProfiles);
 	}
 
 	private void postProcessUsingLegacyApplicationListener(ConfigurableEnvironment environment,
@@ -103,7 +109,7 @@ LegacyConfigFileApplicationListener getLegacyListener() {
 	 * @param environment the environment to apply {@link ConfigData} to
 	 */
 	public static void applyTo(ConfigurableEnvironment environment) {
-		applyTo(environment, null, Collections.emptyList());
+		applyTo(environment, null, null, Collections.emptyList());
 	}
 
 	/**
@@ -112,11 +118,13 @@ public static void applyTo(ConfigurableEnvironment environment) {
 	 * directly and not necessarily as part of a {@link SpringApplication}.
 	 * @param environment the environment to apply {@link ConfigData} to
 	 * @param resourceLoader the resource loader to use
+	 * @param bootstrapRegistry the bootstrap registry to use or {@code null} to use a
+	 * throw-away registry
 	 * @param additionalProfiles any additional profiles that should be applied
 	 */
 	public static void applyTo(ConfigurableEnvironment environment, ResourceLoader resourceLoader,
-			String... additionalProfiles) {
-		applyTo(environment, resourceLoader, Arrays.asList(additionalProfiles));
+			BootstrapRegistry bootstrapRegistry, String... additionalProfiles) {
+		applyTo(environment, resourceLoader, bootstrapRegistry, Arrays.asList(additionalProfiles));
 	}
 
 	/**
@@ -125,13 +133,17 @@ public static void applyTo(ConfigurableEnvironment environment, ResourceLoader r
 	 * directly and not necessarily as part of a {@link SpringApplication}.
 	 * @param environment the environment to apply {@link ConfigData} to
 	 * @param resourceLoader the resource loader to use
+	 * @param bootstrapRegistry the bootstrap registry to use or {@code null} to use a
+	 * throw-away registry
 	 * @param additionalProfiles any additional profiles that should be applied
 	 */
 	public static void applyTo(ConfigurableEnvironment environment, ResourceLoader resourceLoader,
-			Collection<String> additionalProfiles) {
-		new ConfigDataEnvironmentPostProcessor(Supplier::get).postProcessEnvironment(environment, resourceLoader,
-				additionalProfiles);
-
+			BootstrapRegistry bootstrapRegistry, Collection<String> additionalProfiles) {
+		DeferredLogFactory logFactory = Supplier::get;
+		bootstrapRegistry = (bootstrapRegistry != null) ? bootstrapRegistry : new DefaultBootstrapRegisty();
+		ConfigDataEnvironmentPostProcessor postProcessor = new ConfigDataEnvironmentPostProcessor(logFactory,
+				bootstrapRegistry);
+		postProcessor.postProcessEnvironment(environment, resourceLoader, additionalProfiles);
 	}
 
 	@SuppressWarnings("deprecation")

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataImporter.java

@@ -55,26 +55,29 @@ class ConfigDataImporter {
 	 * previously loaded.
 	 * @param activationContext the activation context
 	 * @param locationResolverContext the location resolver context
+	 * @param loaderContext the loader context
 	 * @param locations the locations to resolve
 	 * @return a map of the loaded locations and data
 	 */
 	Map<ConfigDataLocation, ConfigData> resolveAndLoad(ConfigDataActivationContext activationContext,
-			ConfigDataLocationResolverContext locationResolverContext, List<String> locations) {
+			ConfigDataLocationResolverContext locationResolverContext, ConfigDataLoaderContext loaderContext,
+			List<String> locations) {
 		try {
 			Profiles profiles = (activationContext != null) ? activationContext.getProfiles() : null;
-			return load(this.resolvers.resolveAll(locationResolverContext, locations, profiles));
+			return load(loaderContext, this.resolvers.resolveAll(locationResolverContext, locations, profiles));
 		}
 		catch (IOException ex) {
 			throw new IllegalStateException("IO error on loading imports from " + locations, ex);
 		}
 	}
 
-	private Map<ConfigDataLocation, ConfigData> load(List<ConfigDataLocation> locations) throws IOException {
+	private Map<ConfigDataLocation, ConfigData> load(ConfigDataLoaderContext loaderContext,
+			List<ConfigDataLocation> locations) throws IOException {
 		Map<ConfigDataLocation, ConfigData> result = new LinkedHashMap<>();
 		for (int i = locations.size() - 1; i >= 0; i--) {
 			ConfigDataLocation location = locations.get(i);
 			if (this.loadedLocations.add(location)) {
-				result.put(location, this.loaders.load(location));
+				result.put(location, this.loaders.load(loaderContext, location));
 			}
 		}
 		return Collections.unmodifiableMap(result);

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataLoader.java

@@ -40,19 +40,21 @@ public interface ConfigDataLoader<L extends ConfigDataLocation> {
 
 	/**
 	 * Returns if the specified location can be loaded by this instance.
+	 * @param context the loader context
 	 * @param location the location to check.
 	 * @return if the location is supported by this loader
 	 */
-	default boolean isLoadable(L location) {
+	default boolean isLoadable(ConfigDataLoaderContext context, L location) {
 		return true;
 	}
 
 	/**
 	 * Load {@link ConfigData} for the given location.
+	 * @param context the loader context
 	 * @param location the location to load
 	 * @return the loaded config data or {@code null} if the location should be skipped
 	 * @throws IOException on IO error
 	 */
-	ConfigData load(L location) throws IOException;
+	ConfigData load(ConfigDataLoaderContext context, L location) throws IOException;
 
 }

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataLoaderContext.java

@@ -0,0 +1,37 @@
+/*
+ * 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.context.config;
+
+import org.springframework.boot.env.BootstrapRegistry;
+import org.springframework.boot.env.EnvironmentPostProcessor;
+
+/**
+ * Context provided to {@link ConfigDataLoader} methods.
+ *
+ * @author Phillip Webb
+ * @since 2.4.0
+ */
+public interface ConfigDataLoaderContext {
+
+	/**
+	 * Provides access to the {@link BootstrapRegistry} shared across all
+	 * {@link EnvironmentPostProcessor EnvironmentPostProcessors}.
+	 * @return the bootstrap registry
+	 */
+	BootstrapRegistry getBootstrapRegistry();
+
+}

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataLoaders.java

@@ -80,24 +80,25 @@ private Class<?> getLocationType(ConfigDataLoader<?> loader) {
 	/**
 	 * Load {@link ConfigData} using the first appropriate {@link ConfigDataLoader}.
 	 * @param <L> the config data location type
+	 * @param context the loader context
 	 * @param location the location to load
 	 * @return the loaded {@link ConfigData}
 	 * @throws IOException on IO error
 	 */
-	<L extends ConfigDataLocation> ConfigData load(L location) throws IOException {
-		ConfigDataLoader<L> loader = getLoader(location);
+	<L extends ConfigDataLocation> ConfigData load(ConfigDataLoaderContext context, L location) throws IOException {
+		ConfigDataLoader<L> loader = getLoader(context, location);
 		this.logger.trace(LogMessage.of(() -> "Loading " + location + " using loader " + loader.getClass().getName()));
-		return loader.load(location);
+		return loader.load(context, location);
 	}
 
 	@SuppressWarnings("unchecked")
-	private <L extends ConfigDataLocation> ConfigDataLoader<L> getLoader(L location) {
+	private <L extends ConfigDataLocation> ConfigDataLoader<L> getLoader(ConfigDataLoaderContext context, L location) {
 		ConfigDataLoader<L> result = null;
 		for (int i = 0; i < this.loaders.size(); i++) {
 			ConfigDataLoader<?> candidate = this.loaders.get(i);
 			if (this.locationTypes.get(i).isInstance(location)) {
 				ConfigDataLoader<L> loader = (ConfigDataLoader<L>) candidate;
-				if (loader.isLoadable(location)) {
+				if (loader.isLoadable(context, location)) {
 					if (result != null) {
 						throw new IllegalStateException("Multiple loaders found for location " + location + " ["
 								+ candidate.getClass().getName() + "," + result.getClass().getName() + "]");