Fine-tuned logging of WebSocket close exceptions

Issue: SPR-16409

(cherry picked from commit 8e2be91)

spring-websocket/src/main/java/org/springframework/web/socket/adapter/jetty/JettyWebSocketHandlerAdapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -119,8 +119,8 @@ public class JettyWebSocketHandlerAdapter {
 			this.webSocketHandler.afterConnectionClosed(this.wsSession, closeStatus);
 		}
 		catch (Throwable ex) {
-			if (logger.isErrorEnabled()) {
+			if (logger.isWarnEnabled()) {
-				logger.error("Unhandled error for " + this.wsSession, ex);
+				logger.warn("Unhandled exception after connection closed for " + this, ex);
 			}
 		}
 	}

spring-websocket/src/main/java/org/springframework/web/socket/adapter/standard/StandardWebSocketHandlerAdapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -141,8 +141,8 @@ public class StandardWebSocketHandlerAdapter extends Endpoint {
 			this.handler.afterConnectionClosed(this.wsSession, closeStatus);
 		}
 		catch (Throwable ex) {
-			if (logger.isErrorEnabled()) {
+			if (logger.isWarnEnabled()) {
-				logger.error("Unhandled error for " + this.wsSession, ex);
+				logger.warn("Unhandled on-close exception for " + this.wsSession, ex);
 			}
 		}
 	}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -78,8 +78,8 @@ public class ExceptionWebSocketHandlerDecorator extends WebSocketHandlerDecorato
 			getDelegate().afterConnectionClosed(session, closeStatus);
 		}
 		catch (Throwable ex) {
-			if (logger.isErrorEnabled()) {
+			if (logger.isWarnEnabled()) {
-				logger.error("Unhandled error for " + this, ex);
+				logger.warn("Unhandled exception after connection closed for " + this, ex);
 			}
 		}
 	}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -59,6 +59,7 @@ import org.springframework.web.socket.sockjs.transport.session.StreamingSockJsSe
  * sub-protocol handler to send messages from the application back to the client.
  *
  * @author Rossen Stoyanchev
+ * @author Juergen Hoeller
  * @author Andy Wilkinson
  * @author Artem Bilan
  * @since 4.0
@@ -150,8 +151,8 @@ public class SubProtocolWebSocketHandler
 		for (String protocol : protocols) {
 			SubProtocolHandler replaced = this.protocolHandlerLookup.put(protocol, handler);
 			if (replaced != null && replaced != handler) {
-				throw new IllegalStateException("Can't map " + handler +
+				throw new IllegalStateException("Cannot map " + handler +
-						" to protocol '" + protocol + "'. Already mapped to " + replaced + ".");
+						" to protocol '" + protocol + "': already mapped to " + replaced + ".");
 			}
 		}
 		this.protocolHandlers.add(handler);
@@ -257,8 +258,8 @@ public class SubProtocolWebSocketHandler
 					holder.getSession().close(CloseStatus.GOING_AWAY);
 				}
 				catch (Throwable ex) {
-					if (logger.isErrorEnabled()) {
+					if (logger.isWarnEnabled()) {
-						logger.error("Failed to close '" + holder.getSession() + "': " + ex);
+						logger.warn("Failed to close '" + holder.getSession() + "': " + ex);
 					}
 				}
 			}
@@ -318,7 +319,7 @@ public class SubProtocolWebSocketHandler
 		String sessionId = resolveSessionId(message);
 		if (sessionId == null) {
 			if (logger.isErrorEnabled()) {
-				logger.error("Couldn't find session id in " + message);
+				logger.error("Could not find session id in " + message);
 			}
 			return;
 		}
@@ -397,8 +398,8 @@ public class SubProtocolWebSocketHandler
 		}
 		catch (Exception ex) {
 			// Shouldn't happen
-			logger.error("Failed to obtain session.getAcceptedProtocol(). " +
+			logger.error("Failed to obtain session.getAcceptedProtocol(): " +
-					"Will use the default protocol handler (if configured).", ex);
+					"will use the default protocol handler (if configured).", ex);
 		}
 
 		SubProtocolHandler handler;
@@ -465,8 +466,8 @@ public class SubProtocolWebSocketHandler
 						continue;
 					}
 					WebSocketSession session = holder.getSession();
-					if (logger.isErrorEnabled()) {
+					if (logger.isInfoEnabled()) {
-						logger.error("No messages received after " + timeSinceCreated + " ms. " +
+						logger.info("No messages received after " + timeSinceCreated + " ms. " +
 								"Closing " + holder.getSession() + ".");
 					}
 					try {
@@ -474,8 +475,8 @@ public class SubProtocolWebSocketHandler
 						session.close(CloseStatus.SESSION_NOT_RELIABLE);
 					}
 					catch (Throwable ex) {
-						if (logger.isErrorEnabled()) {
+						if (logger.isWarnEnabled()) {
-							logger.error("Failure while closing " + session, ex);
+							logger.warn("Failed to close unreliable " + session, ex);
 						}
 					}
 				}