diff --git a/spring-messaging/src/main/java/org/springframework/messaging/simp/config/StompBrokerRelayRegistration.java b/spring-messaging/src/main/java/org/springframework/messaging/simp/config/StompBrokerRelayRegistration.java
index 57e78a67119..823302f572b 100644
--- a/spring-messaging/src/main/java/org/springframework/messaging/simp/config/StompBrokerRelayRegistration.java
+++ b/spring-messaging/src/main/java/org/springframework/messaging/simp/config/StompBrokerRelayRegistration.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -223,8 +223,8 @@ public class StompBrokerRelayRegistration extends AbstractBrokerRegistration {
 	}
 
 
+	@Override
 	protected StompBrokerRelayMessageHandler getMessageHandler(SubscribableChannel brokerChannel) {
-
 		StompBrokerRelayMessageHandler handler = new StompBrokerRelayMessageHandler(
 				getClientInboundChannel(), getClientOutboundChannel(),
 				brokerChannel, getDestinationPrefixes());
diff --git a/spring-webmvc/src/main/java/org/springframework/web/servlet/config/AnnotationDrivenBeanDefinitionParser.java b/spring-webmvc/src/main/java/org/springframework/web/servlet/config/AnnotationDrivenBeanDefinitionParser.java
index c4690684655..3ec8bc85084 100644
--- a/spring-webmvc/src/main/java/org/springframework/web/servlet/config/AnnotationDrivenBeanDefinitionParser.java
+++ b/spring-webmvc/src/main/java/org/springframework/web/servlet/config/AnnotationDrivenBeanDefinitionParser.java
@@ -157,7 +157,7 @@ class AnnotationDrivenBeanDefinitionParser implements BeanDefinitionParser {
 			ClassUtils.isPresent("javax.validation.Validator",
 					AnnotationDrivenBeanDefinitionParser.class.getClassLoader());
 
-	private static boolean romePresent =
+	private static final boolean romePresent =
 			ClassUtils.isPresent("com.rometools.rome.feed.WireFeed",
 					AnnotationDrivenBeanDefinitionParser.class.getClassLoader());
 
@@ -197,7 +197,7 @@ class AnnotationDrivenBeanDefinitionParser implements BeanDefinitionParser {
 		handlerMappingDef.getPropertyValues().add("contentNegotiationManager", contentNegotiationManager);
 
 		if (element.hasAttribute("enable-matrix-variables")) {
-			Boolean enableMatrixVariables = Boolean.valueOf(element.getAttribute("enable-matrix-variables"));
+			boolean enableMatrixVariables = Boolean.parseBoolean(element.getAttribute("enable-matrix-variables"));
 			handlerMappingDef.getPropertyValues().add("removeSemicolonContent", !enableMatrixVariables);
 		}
 		else if (element.hasAttribute("enableMatrixVariables")) {
@@ -545,7 +545,7 @@ class AnnotationDrivenBeanDefinitionParser implements BeanDefinitionParser {
 			}
 		}
 
-		if (convertersElement == null || Boolean.valueOf(convertersElement.getAttribute("register-defaults"))) {
+		if (convertersElement == null || Boolean.parseBoolean(convertersElement.getAttribute("register-defaults"))) {
 			messageConverters.setSource(source);
 			messageConverters.add(createConverterDefinition(ByteArrayHttpMessageConverter.class, source));
 
diff --git a/spring-webmvc/src/main/java/org/springframework/web/servlet/config/ResourcesBeanDefinitionParser.java b/spring-webmvc/src/main/java/org/springframework/web/servlet/config/ResourcesBeanDefinitionParser.java
index 8c3540e2450..75875105bd4 100644
--- a/spring-webmvc/src/main/java/org/springframework/web/servlet/config/ResourcesBeanDefinitionParser.java
+++ b/spring-webmvc/src/main/java/org/springframework/web/servlet/config/ResourcesBeanDefinitionParser.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -80,7 +80,7 @@ class ResourcesBeanDefinitionParser implements BeanDefinitionParser {
 
 	private static final String RESOURCE_URL_PROVIDER = "mvcResourceUrlProvider";
 
-	private static final boolean isWebJarsAssetLocatorPresent = ClassUtils.isPresent(
+	private static final boolean webJarsPresent = ClassUtils.isPresent(
 			"org.webjars.WebJarAssetLocator", ResourcesBeanDefinitionParser.class.getClassLoader());
 
 
@@ -329,7 +329,7 @@ class ResourcesBeanDefinitionParser implements BeanDefinitionParser {
 		}
 
 		if (isAutoRegistration) {
-			if (isWebJarsAssetLocatorPresent) {
+			if (webJarsPresent) {
 				RootBeanDefinition webJarsResolverDef = new RootBeanDefinition(WebJarsResourceResolver.class);
 				webJarsResolverDef.setSource(source);
 				webJarsResolverDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
diff --git a/spring-websocket/src/main/java/org/springframework/web/socket/WebSocketSession.java b/spring-websocket/src/main/java/org/springframework/web/socket/WebSocketSession.java
index d8491313146..e4212a426fa 100644
--- a/spring-websocket/src/main/java/org/springframework/web/socket/WebSocketSession.java
+++ b/spring-websocket/src/main/java/org/springframework/web/socket/WebSocketSession.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -114,6 +114,12 @@ public interface WebSocketSession extends Closeable {
 
 	/**
 	 * Send a WebSocket message: either {@link TextMessage} or {@link BinaryMessage}.
+	 * <p><strong>Note:</strong> The underlying standard WebSocket session (JSR-356) does
+	 * not allow concurrent sending. Therefore sending must be synchronized. To ensure
+	 * that, one option is to wrap the {@code WebSocketSession} with the
+	 * {@link org.springframework.web.socket.handler.ConcurrentWebSocketSessionDecorator
+	 * ConcurrentWebSocketSessionDecorator}.
+	 * @see org.springframework.web.socket.handler.ConcurrentWebSocketSessionDecorator
 	 */
 	void sendMessage(WebSocketMessage<?> message) throws IOException;