From e17736dd0aee516600172fb55ab4c4432365b446 Mon Sep 17 00:00:00 2001
From: Rossen Stoyanchev <rstoyanchev@pivotal.io>
Date: Fri, 1 May 2020 16:45:25 +0100
Subject: [PATCH] Error handling improvement in AbstractSockJsSession

Closes gh-24986
---
 .../session/AbstractSockJsSession.java        | 27 ++++++++++++-------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/session/AbstractSockJsSession.java b/spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/session/AbstractSockJsSession.java
index 26dc71ae9ced..3f33a3de8960 100644
--- a/spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/session/AbstractSockJsSession.java
+++ b/spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/session/AbstractSockJsSession.java
@@ -380,23 +380,32 @@ public void delegateConnectionEstablished() throws Exception {
 	public void delegateMessages(String... messages) throws SockJsMessageDeliveryException {
 		for (int i = 0; i < messages.length; i++) {
 			try {
-				if (!isClosed()) {
-					this.handler.handleMessage(this, new TextMessage(messages[i]));
-				}
-				else {
-					List<String> undelivered = getUndelivered(messages, i);
-					if (undelivered.isEmpty()) {
-						return;
-					}
-					throw new SockJsMessageDeliveryException(this.id, undelivered, "Session closed");
+				if (isClosed()) {
+					logUndeliveredMessages(i, messages);
+					return;
 				}
+				this.handler.handleMessage(this, new TextMessage(messages[i]));
 			}
 			catch (Exception ex) {
+				if (isClosed()) {
+					if (logger.isTraceEnabled()) {
+						logger.trace("Failed to handle message '" + messages[i] + "'", ex);
+					}
+					logUndeliveredMessages(i, messages);
+					return;
+				}
 				throw new SockJsMessageDeliveryException(this.id, getUndelivered(messages, i), ex);
 			}
 		}
 	}
 
+	private void logUndeliveredMessages(int index, String[] messages) {
+		List<String> undelivered = getUndelivered(messages, index);
+		if (logger.isTraceEnabled() && !undelivered.isEmpty()) {
+			logger.trace("Dropped inbound message(s) due to closed session: " + undelivered);
+		}
+	}
+
 	private static List<String> getUndelivered(String[] messages, int i) {
 		switch (messages.length - i) {
 			case 0: