Auto-configure a bootstrapExecutor bean to be used by Framework's background bean initialization

If there's no bean named bootstrapExecutor but there's a bean named
applicationTaskExecutor, we create an alias named 'bootstrapExecutor'
for the 'applicationTaskExecutor' bean.

Closes gh-39791

Author: mhalbritter

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/task/TaskExecutionAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2024 the original author or authors.
+ * Copyright 2012-2025 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.
@@ -37,7 +37,8 @@
 @EnableConfigurationProperties(TaskExecutionProperties.class)
 @Import({ TaskExecutorConfigurations.ThreadPoolTaskExecutorBuilderConfiguration.class,
 		TaskExecutorConfigurations.SimpleAsyncTaskExecutorBuilderConfiguration.class,
-		TaskExecutorConfigurations.TaskExecutorConfiguration.class })
+		TaskExecutorConfigurations.TaskExecutorConfiguration.class,
+		TaskExecutorConfigurations.BootstrapExecutorConfiguration.class })
 public class TaskExecutionAutoConfiguration {
 
 	/**

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/task/TaskExecutorConfigurations.java

@@ -20,6 +20,7 @@
 
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.ObjectProvider;
+import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
 import org.springframework.boot.autoconfigure.condition.AnyNestedCondition;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
@@ -162,6 +163,26 @@ public Executor getAsyncExecutor() {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	static class BootstrapExecutorConfiguration {
+
+		private static final String BOOTSTRAP_EXECUTOR_NAME = "bootstrapExecutor";
+
+		@Bean
+		static BeanFactoryPostProcessor bootstrapExecutorAliasPostProcessor() {
+			return (beanFactory) -> {
+				boolean hasBootstrapExecutor = beanFactory.containsBean(BOOTSTRAP_EXECUTOR_NAME);
+				boolean hasApplicationTaskExecutor = beanFactory
+					.containsBean(TaskExecutionAutoConfiguration.APPLICATION_TASK_EXECUTOR_BEAN_NAME);
+				if (!hasBootstrapExecutor && hasApplicationTaskExecutor) {
+					beanFactory.registerAlias(TaskExecutionAutoConfiguration.APPLICATION_TASK_EXECUTOR_BEAN_NAME,
+							BOOTSTRAP_EXECUTOR_NAME);
+				}
+			};
+		}
+
+	}
+
 	static class OnExecutorCondition extends AnyNestedCondition {
 
 		OnExecutorCondition() {

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/task/TaskExecutionAutoConfigurationTests.java

@@ -19,6 +19,8 @@
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Executor;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicReference;
@@ -364,12 +366,6 @@ void enableAsyncUsesAutoConfiguredExecutorWhenModeIsForceAndHasPrimaryCustomTask
 			});
 	}
 
-	private Executor createCustomAsyncExecutor(String threadNamePrefix) {
-		SimpleAsyncTaskExecutor executor = new SimpleAsyncTaskExecutor();
-		executor.setThreadNamePrefix(threadNamePrefix);
-		return executor;
-	}
-
 	@Test
 	void enableAsyncUsesAutoConfiguredOneByDefaultEvenThoughSchedulingIsConfigured() {
 		this.contextRunner.withPropertyValues("spring.task.execution.thread-name-prefix=auto-task-")
@@ -382,6 +378,51 @@ void enableAsyncUsesAutoConfiguredOneByDefaultEvenThoughSchedulingIsConfigured()
 			});
 	}
 
+	@Test
+	void shouldAliasApplicationExecutorToBootstrapExecutor() {
+		this.contextRunner.run((context) -> {
+			String[] aliases = context.getAliases("applicationTaskExecutor");
+			assertThat(aliases).containsExactly("bootstrapExecutor");
+		});
+	}
+
+	@Test
+	void shouldNotAliasIfBootstrapExecutorIsDefined() {
+		ExecutorService executor = Executors.newSingleThreadExecutor();
+		try {
+			this.contextRunner.withBean("applicationTaskExecutor", Executor.class, () -> executor)
+				.withBean("bootstrapExecutor", Executor.class, () -> executor)
+				.run((context) -> {
+					assertThat(context).hasBean("applicationTaskExecutor");
+					String[] aliases = context.getAliases("applicationTaskExecutor");
+					assertThat(aliases).isEmpty();
+				});
+		}
+		finally {
+			executor.shutdownNow();
+		}
+	}
+
+	@Test
+	void shouldNotAliasIfApplicationTaskExecutorIsMissing() {
+		ExecutorService executor = Executors.newSingleThreadExecutor();
+		try {
+			this.contextRunner.withBean("customExecutor", Executor.class, () -> executor).run((context) -> {
+				assertThat(context).doesNotHaveBean("applicationTaskExecutor");
+				assertThat(context).doesNotHaveBean("bootstrapExecutor");
+			});
+		}
+		finally {
+			executor.shutdownNow();
+		}
+	}
+
+	private Executor createCustomAsyncExecutor(String threadNamePrefix) {
+		SimpleAsyncTaskExecutor executor = new SimpleAsyncTaskExecutor();
+		executor.setThreadNamePrefix(threadNamePrefix);
+		return executor;
+	}
+
 	private ContextConsumer<AssertableApplicationContext> assertThreadPoolTaskExecutor(
 			Consumer<ThreadPoolTaskExecutor> taskExecutor) {
 		return (context) -> {