Polish "Ensure that MongoClient's EventLoopGroup is shut down during context close"

See gh-16087

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2018 the original author or authors.
+ * Copyright 2012-2019 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.
@@ -86,19 +86,19 @@ public class MongoReactiveAutoConfiguration {
 
 		@Bean
 		@Order(Ordered.HIGHEST_PRECEDENCE)
-		public MongoClientSettingsBuilderCustomizer nettyDriverCustomizer(
+		public NettyDriverMongoClientSettingsBuilderCustomizer nettyDriverCustomizer(
 				ObjectProvider<MongoClientSettings> settings) {
-			return new EventLoopGroupMongoClientSettingsBuilderCustomizer(settings);
+			return new NettyDriverMongoClientSettingsBuilderCustomizer(settings);
 		}
 
-		private static final class EventLoopGroupMongoClientSettingsBuilderCustomizer
+		private static final class NettyDriverMongoClientSettingsBuilderCustomizer
 				implements MongoClientSettingsBuilderCustomizer, DisposableBean {
 
 			private final ObjectProvider<MongoClientSettings> settings;
 
-			private EventLoopGroup eventLoopGroup;
+			private volatile EventLoopGroup eventLoopGroup;
 
-			private EventLoopGroupMongoClientSettingsBuilderCustomizer(
+			private NettyDriverMongoClientSettingsBuilderCustomizer(
 					ObjectProvider<MongoClientSettings> settings) {
 				this.settings = settings;
 			}

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mongo/MongoReactiveAutoConfigurationTests.java

@@ -91,17 +91,17 @@ public class MongoReactiveAutoConfigurationTests {
 
 	@Test
 	public void nettyStreamFactoryFactoryIsConfiguredAutomatically() {
-		AtomicReference<EventLoopGroup> capture = new AtomicReference<>();
+		AtomicReference<EventLoopGroup> eventLoopGroupReference = new AtomicReference<>();
 		this.contextRunner.run((context) -> {
 			assertThat(context).hasSingleBean(MongoClient.class);
 			StreamFactoryFactory factory = getSettings(context).getStreamFactoryFactory();
 			assertThat(factory).isInstanceOf(NettyStreamFactoryFactory.class);
-			capture.set((EventLoopGroup) ReflectionTestUtils.getField(factory,
-					"eventLoopGroup"));
-			assertThat(capture.get()).isNotNull();
-			assertThat(capture.get().isShutdown()).isFalse();
+			EventLoopGroup eventLoopGroup = (EventLoopGroup) ReflectionTestUtils
+					.getField(factory, "eventLoopGroup");
+			assertThat(eventLoopGroup.isShutdown()).isFalse();
+			eventLoopGroupReference.set(eventLoopGroup);
 		});
-		assertThat(capture.get().isShutdown()).isTrue();
+		assertThat(eventLoopGroupReference.get().isShutdown()).isTrue();
 	}
 
 	@Test