Polish "Allow Netty default leak detection to be overidden"

See gh-32144

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2021 the original author or authors.
+ * 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.
@@ -30,9 +30,11 @@ import org.springframework.boot.context.properties.ConfigurationProperties;
 public class NettyProperties {
 
 	/**
-	 * Level of leak detection for reference-counted buffers.
+	 * Level of leak detection for reference-counted buffers. If not configured via
+	 * 'ResourceLeakDetector.setLevel' or the 'io.netty.leakDetection.level' system
+	 * property, default to 'simple'.
 	 */
-	private LeakDetection leakDetection = null;
+	private LeakDetection leakDetection;
 
 	public LeakDetection getLeakDetection() {
 		return this.leakDetection;

spring-boot-project/spring-boot-autoconfigure/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -1736,11 +1736,6 @@
       "name": "spring.neo4j.uri",
       "defaultValue": "bolt://localhost:7687"
     },
-    {
-      "name": "spring.netty.leak-detection",
-      "description": "When null, fall back to Netty system default 'simple' or value of -Dio.netty.leakDetection.level. When set, this will overrride value of -Dio.netty.leakDetection.level",
-      "defaultValue": "null"
-    },
     {
       "name": "spring.quartz.jdbc.comment-prefix",
       "defaultValue": [

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/netty/NettyPropertiesTests.java

@@ -0,0 +1,41 @@
+/*
+ * 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.autoconfigure.netty;
+
+import io.netty.util.ResourceLeakDetector;
+import io.netty.util.ResourceLeakDetector.Level;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.test.util.ReflectionTestUtils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link NettyProperties}
+ *
+ * @author Brian Clozel
+ */
+class NettyPropertiesTests {
+
+	@Test
+	void defaultValueShouldBeConsistent() {
+		ResourceLeakDetector.Level defaultLevel = (Level) ReflectionTestUtils.getField(ResourceLeakDetector.class,
+				"DEFAULT_LEVEL");
+		assertThat(defaultLevel).isEqualTo(Level.SIMPLE);
+	}
+
+}