Example: Fixed an exception log on closed connections.

If the tab was already close message sending failed on null
connections.

Author: newgro

wicket-spring-boot-starter/src/main/java/com/giffing/wicket/spring/boot/starter/web/servlet/websocket/WebSocketMessageSenderDefault.java

@@ -1,5 +1,8 @@
 package com.giffing.wicket.spring.boot.starter.web.servlet.websocket;
 
+import java.util.Collection;
+import java.util.Objects;
+
 import org.apache.wicket.Application;
 import org.apache.wicket.protocol.ws.WebSocketSettings;
 import org.apache.wicket.protocol.ws.api.IWebSocketConnection;
@@ -25,12 +28,18 @@ public void sendToAll(IWebSocketPushMessage event) {
         var webSocketSettings = WebSocketSettings.Holder.get(application);
         var connectionRegistry = webSocketSettings.getConnectionRegistry();
         var connections = connectionRegistry.getConnections(application);
-        log.trace("sending event to {} connections", connections.size());
-        for (IWebSocketConnection connection : connections) {
-            connection.sendMessage(event);
-        }
+        sendMessage(event, connections);
     }
 
+	private void sendMessage(IWebSocketPushMessage event, Collection<IWebSocketConnection> connections) {
+		log.trace("sending event to {} connections", connections.size());
+		connections.stream()
+        .filter(Objects::nonNull)
+        .forEach(connection ->
+       	    connection.sendMessage(event)
+        );
+	}
+
     @Override
     public void sendTo(Object identifier, IWebSocketPushMessage event) {
         if (identifier == null) {
@@ -41,10 +50,7 @@ public void sendTo(Object identifier, IWebSocketPushMessage event) {
         var connectionRegistry = webSocketSettings.getConnectionRegistry();
         wicketSessionResolver.resolve(identifier).forEach(sessionId -> {
             var connections = connectionRegistry.getConnections(application, sessionId);
-            log.trace("sending event to {} connections", connections.size());
-            for (IWebSocketConnection connection : connections) {
-                connection.sendMessage(event);
-            }
+            sendMessage(event, connections);
         });
     }
 }