Update SpringBootContextLoader to support AOT

Update `SpringBootContextLoader` so that it now implements the
`AotContextLoader` interface. The `ContextLoaderHook` will abandon
at `contextLoaded` if the test class is being AOT processed.

This commit also introduces a new `AotApplicationContextInitializer`
which allows us to plug-in an alternative AOT application context
listener when the `SpringApplication` is running in test mode.

Closes gh-31965

spring-boot-project/spring-boot-test/build.gradle

@@ -55,6 +55,7 @@ dependencies {
 	testImplementation("org.slf4j:slf4j-api")
 	testImplementation("org.spockframework:spock-core")
 	testImplementation("org.springframework:spring-webmvc")
+	testImplementation("org.springframework:spring-core-test")
 	testImplementation("org.testng:testng")
 
 	testRuntimeOnly("org.junit.vintage:junit-vintage-engine")

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

@@ -23,6 +23,7 @@ import java.util.Arrays;
 import java.util.List;
 
 import org.springframework.beans.BeanUtils;
+import org.springframework.boot.AotApplicationContextInitializer;
 import org.springframework.boot.ApplicationContextFactory;
 import org.springframework.boot.ConfigurableBootstrapContext;
 import org.springframework.boot.SpringApplication;
@@ -55,6 +56,8 @@ import org.springframework.test.context.ContextConfigurationAttributes;
 import org.springframework.test.context.ContextCustomizer;
 import org.springframework.test.context.ContextLoader;
 import org.springframework.test.context.MergedContextConfiguration;
+import org.springframework.test.context.SmartContextLoader;
+import org.springframework.test.context.aot.AotContextLoader;
 import org.springframework.test.context.support.AbstractContextLoader;
 import org.springframework.test.context.support.AnnotationConfigContextLoaderUtils;
 import org.springframework.test.context.support.TestPropertySourceUtils;
@@ -90,15 +93,31 @@ import org.springframework.web.context.support.GenericWebApplicationContext;
  * @since 1.4.0
  * @see SpringBootTest
  */
-public class SpringBootContextLoader extends AbstractContextLoader {
+public class SpringBootContextLoader extends AbstractContextLoader implements AotContextLoader {
 
 	@Override
 	public ApplicationContext loadContext(MergedContextConfiguration mergedConfig) throws Exception {
+		return loadContext(mergedConfig, Mode.STANDARD, null);
+	}
+
+	@Override
+	public ApplicationContext loadContextForAotProcessing(MergedContextConfiguration mergedConfig) throws Exception {
+		return loadContext(mergedConfig, Mode.AOT_PROCESSING, null);
+	}
+
+	@Override
+	public ApplicationContext loadContextForAotRuntime(MergedContextConfiguration mergedConfig,
+			ApplicationContextInitializer<ConfigurableApplicationContext> initializer) throws Exception {
+		return loadContext(mergedConfig, Mode.AOT_RUNTIME, initializer);
+	}
+
+	private ApplicationContext loadContext(MergedContextConfiguration mergedConfig, Mode mode,
+			ApplicationContextInitializer<ConfigurableApplicationContext> initializer) {
 		assertHasClassesOrLocations(mergedConfig);
 		SpringBootTestAnnotation annotation = SpringBootTestAnnotation.get(mergedConfig);
 		String[] args = annotation.getArgs();
 		UseMainMethod useMainMethod = annotation.getUseMainMethod();
-		ContextLoaderHook hook = new ContextLoaderHook(mergedConfig);
+		ContextLoaderHook hook = new ContextLoaderHook(mergedConfig, mode, initializer);
 		if (useMainMethod != UseMainMethod.NEVER) {
 			Method mainMethod = getMainMethod(mergedConfig, useMainMethod);
 			if (mainMethod != null) {
@@ -297,6 +316,31 @@ public class SpringBootContextLoader extends AbstractContextLoader {
 		throw new IllegalStateException();
 	}
 
+	/**
+	 * Modes that the {@link SpringBootContextLoader} can operate.
+	 */
+	private enum Mode {
+
+		/**
+		 * Load for regular usage.
+		 * @see SmartContextLoader#loadContext
+		 */
+		STANDARD,
+
+		/**
+		 * Load for AOT processing.
+		 * @see AotContextLoader#loadContextForAotProcessing
+		 */
+		AOT_PROCESSING,
+
+		/**
+		 * Load for AOT runtime.
+		 * @see AotContextLoader#loadContextForAotRuntime
+		 */
+		AOT_RUNTIME
+
+	}
+
 	/**
 	 * Inner class to configure {@link WebMergedContextConfiguration}.
 	 */
@@ -417,8 +461,15 @@ public class SpringBootContextLoader extends AbstractContextLoader {
 
 		private final MergedContextConfiguration mergedConfig;
 
-		ContextLoaderHook(MergedContextConfiguration mergedConfig) {
+		private final Mode mode;
+
+		private final ApplicationContextInitializer<ConfigurableApplicationContext> initializer;
+
+		ContextLoaderHook(MergedContextConfiguration mergedConfig, Mode mode,
+				ApplicationContextInitializer<ConfigurableApplicationContext> initializer) {
 			this.mergedConfig = mergedConfig;
+			this.mode = mode;
+			this.initializer = initializer;
 		}
 
 		@Override
@@ -428,6 +479,17 @@ public class SpringBootContextLoader extends AbstractContextLoader {
 				@Override
 				public void starting(ConfigurableBootstrapContext bootstrapContext) {
 					SpringBootContextLoader.this.configure(ContextLoaderHook.this.mergedConfig, application);
+					if (ContextLoaderHook.this.initializer != null) {
+						application.addInitializers(
+								AotApplicationContextInitializer.of(ContextLoaderHook.this.initializer));
+					}
+				}
+
+				@Override
+				public void contextLoaded(ConfigurableApplicationContext context) {
+					if (ContextLoaderHook.this.mode == Mode.AOT_PROCESSING) {
+						throw new AbandonedRunException(context);
+					}
 				}
 
 				@Override

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

@@ -49,6 +49,7 @@ import org.springframework.test.context.TestContext;
 import org.springframework.test.context.TestContextAnnotationUtils;
 import org.springframework.test.context.TestContextBootstrapper;
 import org.springframework.test.context.TestExecutionListener;
+import org.springframework.test.context.aot.AotTestAttributes;
 import org.springframework.test.context.support.DefaultTestContextBootstrapper;
 import org.springframework.test.context.support.TestPropertySourceUtils;
 import org.springframework.test.context.web.WebAppConfiguration;
@@ -97,6 +98,16 @@ public class SpringBootTestContextBootstrapper extends DefaultTestContextBootstr
 
 	private static final Log logger = LogFactory.getLog(SpringBootTestContextBootstrapper.class);
 
+	private final AotTestAttributes aotTestAttributes;
+
+	public SpringBootTestContextBootstrapper() {
+		this(AotTestAttributes.getInstance());
+	}
+
+	SpringBootTestContextBootstrapper(AotTestAttributes aotTestAttributes) {
+		this.aotTestAttributes = aotTestAttributes;
+	}
+
 	@Override
 	public TestContext buildTestContext() {
 		TestContext context = super.buildTestContext();
@@ -231,14 +242,25 @@ public class SpringBootTestContextBootstrapper extends DefaultTestContextBootstr
 		if (containsNonTestComponent(classes) || mergedConfig.hasLocations()) {
 			return classes;
 		}
-		Class<?> found = new AnnotatedClassFinder(SpringBootConfiguration.class)
-				.findFromClass(mergedConfig.getTestClass());
+		Class<?> found = findConfigurationClass(mergedConfig.getTestClass());
 		Assert.state(found != null, "Unable to find a @SpringBootConfiguration, you need to use "
 				+ "@ContextConfiguration or @SpringBootTest(classes=...) with your test");
 		logger.info("Found @SpringBootConfiguration " + found.getName() + " for test " + mergedConfig.getTestClass());
 		return merge(found, classes);
 	}
 
+	private Class<?> findConfigurationClass(Class<?> testClass) {
+		String propertyName = "%s.SpringBootConfiguration.%s"
+				.formatted(SpringBootTestContextBootstrapper.class.getName(), testClass.getName());
+		String foundClassName = this.aotTestAttributes.getString(propertyName);
+		if (foundClassName != null) {
+			return ClassUtils.resolveClassName(foundClassName, testClass.getClassLoader());
+		}
+		Class<?> found = new AnnotatedClassFinder(SpringBootConfiguration.class).findFromClass(testClass);
+		this.aotTestAttributes.setAttribute(propertyName, found.getName());
+		return found;
+	}
+
 	private boolean containsNonTestComponent(Class<?>[] classes) {
 		for (Class<?> candidate : classes) {
 			if (!MergedAnnotations.from(candidate, SearchStrategy.INHERITED_ANNOTATIONS)

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

@@ -0,0 +1,112 @@
+/*
+ * Copyright 2012-2022 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.test.context;
+
+import java.util.stream.Stream;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.aot.AotDetector;
+import org.springframework.aot.generate.InMemoryGeneratedFiles;
+import org.springframework.aot.test.generate.compile.CompileWithTargetClassAccess;
+import org.springframework.aot.test.generate.compile.TestCompiler;
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.beans.factory.support.GenericBeanDefinition;
+import org.springframework.boot.SpringBootConfiguration;
+import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
+import org.springframework.context.ApplicationContextInitializer;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.Import;
+import org.springframework.context.support.GenericApplicationContext;
+import org.springframework.test.context.BootstrapUtils;
+import org.springframework.test.context.MergedContextConfiguration;
+import org.springframework.test.context.TestContextBootstrapper;
+import org.springframework.test.context.aot.AotContextLoader;
+import org.springframework.test.context.aot.AotTestContextInitializers;
+import org.springframework.test.context.aot.TestContextAotGenerator;
+import org.springframework.test.util.ReflectionTestUtils;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.function.ThrowingConsumer;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link SpringBootContextLoader} when used in AOT mode.
+ *
+ * @author Phillip Webb
+ */
+@CompileWithTargetClassAccess
+class SpringBootContextLoaderAotTests {
+
+	@Test
+	void loadContextForAotProcessingAndAotRuntime() {
+		InMemoryGeneratedFiles generatedFiles = new InMemoryGeneratedFiles();
+		TestContextAotGenerator generator = new TestContextAotGenerator(generatedFiles);
+		Class<?> testClass = ExampleTest.class;
+		generator.processAheadOfTime(Stream.of(testClass));
+		TestCompiler.forSystem().withFiles(generatedFiles).printFiles(System.out)
+				.compile(ThrowingConsumer.of((compiled) -> assertCompiledTest(testClass)));
+	}
+
+	private void assertCompiledTest(Class<?> testClass) throws Exception {
+		try {
+			System.setProperty(AotDetector.AOT_ENABLED, "true");
+			resetAotClasses();
+			AotTestContextInitializers aotContextInitializers = new AotTestContextInitializers();
+			TestContextBootstrapper testContextBootstrapper = BootstrapUtils.resolveTestContextBootstrapper(testClass);
+			MergedContextConfiguration mergedConfig = testContextBootstrapper.buildMergedContextConfiguration();
+			ApplicationContextInitializer<ConfigurableApplicationContext> contextInitializer = aotContextInitializers
+					.getContextInitializer(testClass);
+			ConfigurableApplicationContext context = (ConfigurableApplicationContext) ((AotContextLoader) mergedConfig
+					.getContextLoader()).loadContextForAotRuntime(mergedConfig, contextInitializer);
+			assertThat(context).isExactlyInstanceOf(GenericApplicationContext.class);
+			String[] beanNames = context.getBeanNamesForType(ExampleBean.class);
+			BeanDefinition beanDefinition = context.getBeanFactory().getBeanDefinition(beanNames[0]);
+			assertThat(beanDefinition).isNotExactlyInstanceOf(GenericBeanDefinition.class);
+		}
+		finally {
+			System.clearProperty(AotDetector.AOT_ENABLED);
+			resetAotClasses();
+		}
+	}
+
+	private void resetAotClasses() {
+		reset("org.springframework.test.context.aot.AotTestAttributesFactory");
+		reset("org.springframework.test.context.aot.AotTestContextInitializersFactory");
+	}
+
+	private void reset(String className) {
+		Class<?> targetClass = ClassUtils.resolveClassName(className, null);
+		ReflectionTestUtils.invokeMethod(targetClass, "reset");
+	}
+
+	@SpringBootTest(classes = ExampleConfig.class, webEnvironment = WebEnvironment.NONE)
+	static class ExampleTest {
+
+	}
+
+	@SpringBootConfiguration
+	@Import(ExampleBean.class)
+	static class ExampleConfig {
+
+	}
+
+	static class ExampleBean {
+
+	}
+
+}

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/AotApplicationContextInitializer.java

@@ -0,0 +1,152 @@
+/*
+ * Copyright 2012-2022 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;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import org.springframework.beans.BeanUtils;
+import org.springframework.context.ApplicationContextInitializer;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.core.log.LogMessage;
+import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
+
+/**
+ * A {@link ApplicationContextInitializer} wrapper used to initialize a
+ * {@link ConfigurableApplicationContext} using artifacts that were generated
+ * ahead-of-time.
+ *
+ * @param <C> the application context type
+ * @author Phillip Webb
+ * @since 3.0.0
+ */
+public abstract sealed class AotApplicationContextInitializer<C extends ConfigurableApplicationContext>
+		implements ApplicationContextInitializer<C> {
+
+	private static final Log logger = LogFactory.getLog(AotApplicationContextInitializer.class);
+
+	@Override
+	public final void initialize(C applicationContext) {
+		logger.debug(LogMessage.format("Initializing ApplicationContext using AOT initializer '%s'", getName()));
+		aotInitialize(applicationContext);
+	}
+
+	abstract void aotInitialize(C applicationContext);
+
+	abstract String getName();
+
+	static <C extends ConfigurableApplicationContext> AotApplicationContextInitializer<C> forMainApplicationClass(
+			Class<?> mainApplicationClass) {
+		String initializerClassName = mainApplicationClass.getName() + "__ApplicationContextInitializer";
+		return new ReflectionDelegatingAotApplicationContextInitializer<>(initializerClassName);
+	}
+
+	/**
+	 * Create a new {@link AotApplicationContextInitializer} by delegating to an existing
+	 * initializer instance.
+	 * @param <C> the application context type
+	 * @param initializer the initializer to delegate to
+	 * @return a new {@link AotApplicationContextInitializer} instance
+	 */
+	public static <C extends ConfigurableApplicationContext> AotApplicationContextInitializer<C> of(
+			ApplicationContextInitializer<C> initializer) {
+		Assert.notNull(initializer, "Initializer must not be null");
+		return new InstanceDelegatingAotApplicationContextInitializer<>(initializer.getClass().getName(), initializer);
+	}
+
+	/**
+	 * Create a new {@link AotApplicationContextInitializer} by delegating to an existing
+	 * initializer instance.
+	 * @param <C> the application context type
+	 * @param initializer the initializer to delegate to
+	 * @param name the name of the initializer
+	 * @return a new {@link AotApplicationContextInitializer} instance
+	 */
+	public static <C extends ConfigurableApplicationContext> AotApplicationContextInitializer<C> of(String name,
+			ApplicationContextInitializer<C> initializer) {
+		Assert.notNull(name, "Name must not be null");
+		Assert.notNull(initializer, "Initializer must not be null");
+		return new InstanceDelegatingAotApplicationContextInitializer<>(name, initializer);
+	}
+
+	/**
+	 * {@link AotApplicationContextInitializer} that delegates to an initializer created
+	 * via reflection.
+	 *
+	 * @param <C> the application context type
+	 */
+	static final class ReflectionDelegatingAotApplicationContextInitializer<C extends ConfigurableApplicationContext>
+			extends AotApplicationContextInitializer<C> {
+
+		private final String initializerClassName;
+
+		ReflectionDelegatingAotApplicationContextInitializer(String initializerClassName) {
+			this.initializerClassName = initializerClassName;
+		}
+
+		@Override
+		void aotInitialize(C applicationContext) {
+			ApplicationContextInitializer<C> initializer = createInitializer(applicationContext.getClassLoader());
+			initializer.initialize(applicationContext);
+		}
+
+		@SuppressWarnings("unchecked")
+		private ApplicationContextInitializer<C> createInitializer(ClassLoader classLoader) {
+			Class<?> initializerClass = ClassUtils.resolveClassName(this.initializerClassName, classLoader);
+			Assert.isAssignable(ApplicationContextInitializer.class, initializerClass);
+			return (ApplicationContextInitializer<C>) BeanUtils.instantiateClass(initializerClass);
+		}
+
+		@Override
+		String getName() {
+			return this.initializerClassName;
+		}
+
+	}
+
+	/**
+	 * {@link AotApplicationContextInitializer} that delegates to an existing initializer
+	 * instance.
+	 *
+	 * @param <C> the application context type
+	 */
+	static final class InstanceDelegatingAotApplicationContextInitializer<C extends ConfigurableApplicationContext>
+			extends AotApplicationContextInitializer<C> {
+
+		private final String name;
+
+		private final ApplicationContextInitializer<C> initializer;
+
+		InstanceDelegatingAotApplicationContextInitializer(String name, ApplicationContextInitializer<C> initializer) {
+			this.name = name;
+			this.initializer = initializer;
+		}
+
+		@Override
+		void aotInitialize(C applicationContext) {
+			this.initializer.initialize(applicationContext);
+		}
+
+		@Override
+		String getName() {
+			return this.name;
+		}
+
+	}
+
+}

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/SpringApplication.java

@@ -67,7 +67,6 @@ import org.springframework.context.annotation.AnnotationConfigApplicationContext
 import org.springframework.context.annotation.AnnotationConfigUtils;
 import org.springframework.context.annotation.ClassPathBeanDefinitionScanner;
 import org.springframework.context.annotation.ConfigurationClassPostProcessor;
-import org.springframework.context.aot.ApplicationContextAotInitializer;
 import org.springframework.context.support.AbstractApplicationContext;
 import org.springframework.context.support.GenericApplicationContext;
 import org.springframework.core.GenericTypeResolver;
@@ -86,6 +85,7 @@ import org.springframework.core.io.DefaultResourceLoader;
 import org.springframework.core.io.ResourceLoader;
 import org.springframework.core.io.support.SpringFactoriesLoader;
 import org.springframework.core.io.support.SpringFactoriesLoader.ArgumentResolver;
+import org.springframework.core.log.LogMessage;
 import org.springframework.core.metrics.ApplicationStartup;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
@@ -416,12 +416,22 @@ public class SpringApplication {
 
 	private void addAotGeneratedInitializerIfNecessary(List<ApplicationContextInitializer<?>> initializers) {
 		if (AotDetector.useGeneratedArtifacts()) {
-			String initializerClassName = this.mainApplicationClass.getName() + "__ApplicationContextInitializer";
-			if (logger.isDebugEnabled()) {
-				logger.debug("Using AOT generated initializer: " + initializerClassName);
+			List<AotApplicationContextInitializer<?>> aotInitializers = new ArrayList<>();
+			for (ApplicationContextInitializer<?> candidate : initializers) {
+				if (candidate instanceof AotApplicationContextInitializer<?> aotInitializer) {
+					aotInitializers.add(aotInitializer);
+				}
+			}
+			if (aotInitializers.isEmpty()) {
+				AotApplicationContextInitializer<?> aotInitializer = AotApplicationContextInitializer
+						.forMainApplicationClass(this.mainApplicationClass);
+				aotInitializers.add(aotInitializer);
+			}
+			for (AotApplicationContextInitializer<?> aotInitializer : aotInitializers) {
+				logger.debug(LogMessage.format("Using AOT generated initializer: %s", aotInitializer.getName()));
 			}
-			initializers.add(0,
-					(context) -> new ApplicationContextAotInitializer().initialize(context, initializerClassName));
+			initializers.removeAll(aotInitializers);
+			initializers.addAll(0, aotInitializers);
 		}
 	}
 

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/AotApplicationContextInitializerTests.java

@@ -0,0 +1,99 @@
+/*
+ * Copyright 2012-2022 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;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.context.ApplicationContextInitializer;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.support.GenericApplicationContext;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+
+/**
+ * Tests for {@link AotApplicationContextInitializer}.
+ *
+ * @author Phillip Webb
+ */
+class AotApplicationContextInitializerTests {
+
+	@Test
+	void forMainApplicationClassUsesReflection() {
+		AotApplicationContextInitializer<ConfigurableApplicationContext> initializer = AotApplicationContextInitializer
+				.forMainApplicationClass(ExampleMain.class);
+		GenericApplicationContext applicationContext = new GenericApplicationContext();
+		initializer.initialize(applicationContext);
+		assertThat(initializer.getName()).isEqualTo(ExampleMain__ApplicationContextInitializer.class.getName());
+		assertThat(applicationContext.getId()).isEqualTo("ExampleMain");
+	}
+
+	@Test
+	void ofWhenInitializerIsNullThrowsException() {
+		assertThatIllegalArgumentException().isThrownBy(() -> AotApplicationContextInitializer.of(null))
+				.withMessage("Initializer must not be null");
+	}
+
+	@Test
+	void ofWithNameWhenInitializerIsNullThrowsException() {
+		assertThatIllegalArgumentException().isThrownBy(() -> AotApplicationContextInitializer.of("test", null))
+				.withMessage("Initializer must not be null");
+	}
+
+	@Test
+	void ofWithNameWhenNameIsNullThrowsException() {
+		assertThatIllegalArgumentException()
+				.isThrownBy(() -> AotApplicationContextInitializer.of(null, new CustomApplicationContextInitializer()))
+				.withMessage("Name must not be null");
+	}
+
+	@Test
+	void ofUsesDelegation() {
+		AotApplicationContextInitializer<ConfigurableApplicationContext> initializer = AotApplicationContextInitializer
+				.of(new CustomApplicationContextInitializer());
+		GenericApplicationContext applicationContext = new GenericApplicationContext();
+		initializer.initialize(applicationContext);
+		assertThat(initializer.getName()).isEqualTo(CustomApplicationContextInitializer.class.getName());
+		assertThat(applicationContext.getId()).isEqualTo("Custom");
+
+	}
+
+	static class ExampleMain {
+
+	}
+
+	static class ExampleMain__ApplicationContextInitializer
+			implements ApplicationContextInitializer<ConfigurableApplicationContext> {
+
+		@Override
+		public void initialize(ConfigurableApplicationContext applicationContext) {
+			applicationContext.setId("ExampleMain");
+		}
+
+	}
+
+	static class CustomApplicationContextInitializer
+			implements ApplicationContextInitializer<ConfigurableApplicationContext> {
+
+		@Override
+		public void initialize(ConfigurableApplicationContext applicationContext) {
+			applicationContext.setId("Custom");
+		}
+
+	}
+
+}