Polish "Polish SpringApplicationAdminJmxAutoConfigurationTests"

See gh-26416

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

@@ -36,13 +36,13 @@ import org.springframework.jmx.export.MBeanExporter;
  *
  * @author Stephane Nicoll
  * @author Andy Wilkinson
- * @author Nguyen Bao Sach
  * @since 1.3.0
  * @see SpringApplicationAdminMXBean
  */
 @Configuration(proxyBeanMethods = false)
 @AutoConfigureAfter(JmxAutoConfiguration.class)
-@ConditionalOnProperty(prefix = "spring.application.admin", value = "enabled", havingValue = "true")
+@ConditionalOnProperty(prefix = "spring.application.admin", value = "enabled", havingValue = "true",
+		matchIfMissing = false)
 public class SpringApplicationAdminJmxAutoConfiguration {
 
 	/**
@@ -61,8 +61,11 @@ public class SpringApplicationAdminJmxAutoConfiguration {
 	public SpringApplicationAdminMXBeanRegistrar springApplicationAdminRegistrar(
 			ObjectProvider<MBeanExporter> mbeanExporters, Environment environment) throws MalformedObjectNameException {
 		String jmxName = environment.getProperty(JMX_NAME_PROPERTY, DEFAULT_JMX_NAME);
-		// Make sure to not register that MBean twice
-		mbeanExporters.forEach((mbeanExporter) -> mbeanExporter.addExcludedBean(jmxName));
+		if (mbeanExporters != null) { // Make sure to not register that MBean twice
+			for (MBeanExporter mbeanExporter : mbeanExporters) {
+				mbeanExporter.addExcludedBean(jmxName);
+			}
+		}
 		return new SpringApplicationAdminMXBeanRegistrar(jmxName);
 	}
 

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/admin/SpringApplicationAdminJmxAutoConfigurationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -64,7 +64,7 @@ class SpringApplicationAdminJmxAutoConfigurationTests {
 			.withConfiguration(AutoConfigurations.of(SpringApplicationAdminJmxAutoConfiguration.class));
 
 	@Test
-	void WhenThereAreNotAnyMBeanExporters() {
+	void notRegisteredWhenThereAreNoMBeanExporter() {
 		this.contextRunner.withPropertyValues(ENABLE_ADMIN_PROP).run((context) -> {
 			ObjectName objectName = createDefaultObjectName();
 			ObjectInstance objectInstance = this.server.getObjectInstance(objectName);