Merge branch '2.2.x' into 2.3.x

Closes gh-22580

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

 /*
- * Copyright 2012-2019 the original author or authors.
+ * 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.
@@ -23,9 +23,9 @@ import java.util.concurrent.atomic.AtomicBoolean;
 import javax.validation.Configuration;
 import javax.validation.Validation;
 
+import org.springframework.boot.context.event.ApplicationEnvironmentPreparedEvent;
 import org.springframework.boot.context.event.ApplicationFailedEvent;
 import org.springframework.boot.context.event.ApplicationReadyEvent;
-import org.springframework.boot.context.event.ApplicationStartingEvent;
 import org.springframework.boot.context.event.SpringApplicationEvent;
 import org.springframework.boot.context.logging.LoggingApplicationListener;
 import org.springframework.context.ApplicationListener;
@@ -66,7 +66,7 @@ public class BackgroundPreinitializer implements ApplicationListener<SpringAppli
 	@Override
 	public void onApplicationEvent(SpringApplicationEvent event) {
 		if (!Boolean.getBoolean(IGNORE_BACKGROUNDPREINITIALIZER_PROPERTY_NAME)
-				&& event instanceof ApplicationStartingEvent && multipleProcessors()
+				&& event instanceof ApplicationEnvironmentPreparedEvent && multipleProcessors()
 				&& preinitializationStarted.compareAndSet(false, true)) {
 			performPreinitialization();
 		}