Polish "Avoid using reflection when configuring Tomcat listener"

See gh-22329

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/websocket/reactive/TomcatWebSocketReactiveWebServerCustomizer.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.
@@ -16,9 +16,8 @@
 
 package org.springframework.boot.autoconfigure.websocket.reactive;
 
-import java.util.Collections;
-
 import org.apache.tomcat.websocket.server.WsSci;
+
 import org.springframework.boot.web.embedded.tomcat.TomcatReactiveWebServerFactory;
 import org.springframework.boot.web.server.WebServerFactoryCustomizer;
 import org.springframework.core.Ordered;
@@ -34,8 +33,7 @@ public class TomcatWebSocketReactiveWebServerCustomizer
 
 	@Override
 	public void customize(TomcatReactiveWebServerFactory factory) {
-		factory.addContextCustomizers((context) ->
-				context.addServletContainerInitializer(new WsSci(), Collections.emptySet()));
+		factory.addContextCustomizers((context) -> context.addServletContainerInitializer(new WsSci(), null));
 	}
 
 	@Override

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/websocket/servlet/TomcatWebSocketServletWebServerCustomizer.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.
@@ -16,9 +16,8 @@
 
 package org.springframework.boot.autoconfigure.websocket.servlet;
 
-import java.util.Collections;
-
 import org.apache.tomcat.websocket.server.WsSci;
+
 import org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory;
 import org.springframework.boot.web.server.WebServerFactoryCustomizer;
 import org.springframework.core.Ordered;
@@ -36,8 +35,7 @@ public class TomcatWebSocketServletWebServerCustomizer
 
 	@Override
 	public void customize(TomcatServletWebServerFactory factory) {
-		factory.addContextCustomizers((context) ->
-				context.addServletContainerInitializer(new WsSci(), Collections.emptySet()));
+		factory.addContextCustomizers((context) -> context.addServletContainerInitializer(new WsSci(), null));
 	}
 
 	@Override