Fix Sonar smells for websocket module

* Introduce `JavaUtils` for chaining properties setting
* Fix method complexity in the `ServerWebSocketContainer` using newly
introduced `JavaUtils`
* Make `JavaUtils` as `final`

spring-integration-core/src/main/java/org/springframework/integration/util/JavaUtils.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://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.integration.util;
+
+import java.util.function.Consumer;
+
+/**
+ * Chained utility methods to simplify some Java repetitive code. Obtain a reference to
+ * the singleton {@link #INSTANCE} and then chain calls to the utility methods.
+ *
+ * @author Gary Russell
+ * @author Artem Bilan
+ *
+ * @since 5.1.3
+ */
+public final class JavaUtils {
+
+	/**
+	 * The singleton instance of this utility class.
+	 */
+	public static final JavaUtils INSTANCE = new JavaUtils();
+
+	private JavaUtils() {
+		super();
+	}
+
+	/**
+	 * Invoke {@link Consumer#accept(Object)} with the value if the condition is true.
+	 * @param condition the condition.
+	 * @param value the value.
+	 * @param consumer the consumer.
+	 * @param <T> the value type.
+	 * @return this.
+	 */
+	public <T> JavaUtils acceptIfCondition(boolean condition, T value, Consumer<T> consumer) {
+		if (condition) {
+			consumer.accept(value);
+		}
+		return this;
+	}
+
+	/**
+	 * Invoke {@link Consumer#accept(Object)} with the value if it is not null.
+	 * @param value the value.
+	 * @param consumer the consumer.
+	 * @param <T> the value type.
+	 * @return this.
+	 */
+	public <T> JavaUtils acceptIfNotNull(T value, Consumer<T> consumer) {
+		if (value != null) {
+			consumer.accept(value);
+		}
+		return this;
+	}
+
+}