Add isOpen to WebSocketSession in WebFlux

Closes gh-26043

spring-webflux/src/main/java/org/springframework/web/reactive/socket/WebSocketSession.java

@@ -80,6 +80,12 @@ public interface WebSocketSession {
 	 */
 	Mono<Void> send(Publisher<WebSocketMessage> messages);
 
+	/**
+	 * Whether the underlying connection is open.
+	 * @since 5.3.1
+	 */
+	boolean isOpen();
+
 	/**
 	 * Close the WebSocket session with {@link CloseStatus#NORMAL}.
 	 */

spring-webflux/src/main/java/org/springframework/web/reactive/socket/adapter/JettyWebSocketSession.java

@@ -113,6 +113,11 @@ else if (WebSocketMessage.Type.PONG.equals(message.getType())) {
 		return true;
 	}
 
+	@Override
+	public boolean isOpen() {
+		return getDelegate().isOpen();
+	}
+
 	@Override
 	public Mono<Void> close(CloseStatus status) {
 		getDelegate().close(status.getCode(), status.getReason());

spring-webflux/src/main/java/org/springframework/web/reactive/socket/adapter/ReactorNettyWebSocketSession.java

@@ -15,10 +15,13 @@
  */
 package org.springframework.web.reactive.socket.adapter;
 
+import java.util.function.Consumer;
+
 import io.netty.handler.codec.http.websocketx.WebSocketFrame;
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
+import reactor.netty.Connection;
 import reactor.netty.NettyInbound;
 import reactor.netty.NettyOutbound;
 import reactor.netty.http.websocket.WebsocketInbound;
@@ -93,6 +96,13 @@ public Mono<Void> send(Publisher<WebSocketMessage> messages) {
 				.then();
 	}
 
+	@Override
+	public boolean isOpen() {
+		DisposedCallback callback = new DisposedCallback();
+		getDelegate().getInbound().withConnection(callback);
+		return callback.isDisposed();
+	}
+
 	@Override
 	public Mono<Void> close(CloseStatus status) {
 		// this will notify WebSocketInbound.receiveCloseStatus()
@@ -129,4 +139,19 @@ public WebsocketOutbound getOutbound() {
 		}
 	}
 
+
+	private static class DisposedCallback implements Consumer<Connection> {
+
+		private boolean disposed;
+
+		public boolean isDisposed() {
+			return this.disposed;
+		}
+
+		@Override
+		public void accept(Connection connection) {
+			this.disposed = connection.isDisposed();
+		}
+	}
+
 }

spring-webflux/src/main/java/org/springframework/web/reactive/socket/adapter/StandardWebSocketSession.java

@@ -103,6 +103,11 @@ else if (WebSocketMessage.Type.PONG.equals(message.getType())) {
 		return true;
 	}
 
+	@Override
+	public boolean isOpen() {
+		return getDelegate().isOpen();
+	}
+
 	@Override
 	public Mono<Void> close(CloseStatus status) {
 		try {

spring-webflux/src/main/java/org/springframework/web/reactive/socket/adapter/UndertowWebSocketSession.java

@@ -108,6 +108,11 @@ else if (WebSocketMessage.Type.PONG.equals(message.getType())) {
 		return true;
 	}
 
+	@Override
+	public boolean isOpen() {
+		return getDelegate().isOpen();
+	}
+
 	@Override
 	public Mono<Void> close(CloseStatus status) {
 		CloseMessage cm = new CloseMessage(status.getCode(), status.getReason());

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

@@ -130,7 +130,7 @@ public interface WebSocketSession extends Closeable {
 	void sendMessage(WebSocketMessage<?> message) throws IOException;
 
 	/**
-	 * Return whether the connection is still open.
+	 * Whether the underlying connection is open.
 	 */
 	boolean isOpen();