Remove incorrect package import

Issue: SPR-10880

spring-messaging/src/main/java/org/springframework/messaging/simp/config/StompEndpointRegistry.java

@@ -26,14 +26,13 @@ import org.springframework.messaging.handler.websocket.SubProtocolWebSocketHandl
 import org.springframework.messaging.simp.handler.MutableUserQueueSuffixResolver;
 import org.springframework.messaging.simp.stomp.StompProtocolHandler;
 import org.springframework.scheduling.TaskScheduler;
+import org.springframework.util.Assert;
 import org.springframework.util.MultiValueMap;
 import org.springframework.web.HttpRequestHandler;
 import org.springframework.web.servlet.HandlerMapping;
 import org.springframework.web.servlet.handler.AbstractHandlerMapping;
 import org.springframework.web.servlet.handler.SimpleUrlHandlerMapping;
 
-import reactor.util.Assert;
-
 
 /**
  * A helper class for configuring STOMP protocol handling over WebSocket.

spring-websocket/src/main/java/org/springframework/web/socket/ReaderTextMessage.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2002-2013 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.web.socket;
+
+/**
+ * A {@link WebSocketMessage} that contains a textual {@link String} payload.
+ *
+ * @author Rossen Stoyanchev
+ * @since 4.0
+ */
+public final class ReaderTextMessage extends WebSocketMessage<String> {
+
+	/**
+	 * Create a new {@link ReaderTextMessage} instance.
+	 * @param payload the non-null payload
+	 */
+	public ReaderTextMessage(CharSequence payload) {
+		super(payload.toString(), true);
+	}
+
+	/**
+	 * Create a new {@link ReaderTextMessage} instance.
+	 * @param payload the non-null payload
+	 * @param isLast whether this the last part of a message received or transmitted in parts
+	 */
+	public ReaderTextMessage(CharSequence payload, boolean isLast) {
+		super(payload.toString(), isLast);
+	}
+
+
+	@Override
+	protected int getPayloadSize() {
+		return getPayload().length();
+	}
+
+	@Override
+	protected String toStringPayload() {
+		return (getPayloadSize() > 10) ? getPayload().substring(0, 10) + ".." : getPayload();
+	}
+
+}