Allow use of @SendToUser even w/o authenticated user

Before this change, subscribing to a user destination and use of
@SendToUser annotation required an authenticated user.

This change makes it possible to subscribe to a user destination from
WebSocket sessions without an authenticated user. In such cases the
destination is associated with one session only rather than with a
user (and all their sessions).

It is then also possible to send a message to a user destination
via "/user/{sessionId}/.." rather than "/user/{user}/...".

That means @SendToUser works relying on the session id of the input
message, effectively sending a reply to destination private to the
session.

A key use case for this is handling an exception with an
@MessageExceptionHandler method and sending a reply with @SendToUser.

Issue: SPR-11309

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

@@ -301,6 +301,7 @@ public class StompSubProtocolHandler implements SubProtocolHandler, ApplicationE
 			String origDestination = stompAccessor.getFirstNativeHeader(SimpMessageHeaderAccessor.ORIGINAL_DESTINATION);
 			if (origDestination != null) {
 				stompAccessor = toMutableAccessor(stompAccessor, message);
+				stompAccessor.removeNativeHeader(SimpMessageHeaderAccessor.ORIGINAL_DESTINATION);
 				stompAccessor.setDestination(origDestination);
 			}
 		}

spring-websocket/src/test/java/org/springframework/web/socket/messaging/StompSubProtocolHandlerTests.java

@@ -246,6 +246,7 @@ public class StompSubProtocolHandlerTests {
 		assertEquals(1, this.session.getSentMessages().size());
 		WebSocketMessage<?> textMessage = this.session.getSentMessages().get(0);
 		assertTrue(((String) textMessage.getPayload()).contains("destination:/user/queue/foo\n"));
+		assertFalse(((String) textMessage.getPayload()).contains(SimpMessageHeaderAccessor.ORIGINAL_DESTINATION));
 	}
 
 	@Test

spring-websocket/src/test/java/org/springframework/web/socket/messaging/StompWebSocketIntegrationTests.java

@@ -36,6 +36,7 @@ import org.springframework.context.annotation.ComponentScan;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.messaging.handler.annotation.MessageExceptionHandler;
 import org.springframework.messaging.handler.annotation.MessageMapping;
+import org.springframework.messaging.simp.annotation.SendToUser;
 import org.springframework.messaging.simp.annotation.SubscribeMapping;
 import org.springframework.messaging.simp.config.MessageBrokerRegistry;
 import org.springframework.messaging.simp.stomp.StompCommand;
@@ -118,10 +119,10 @@ public class StompWebSocketIntegrationTests extends AbstractWebSocketIntegration
 	@Test
 	public void sendMessageToBrokerAndReceiveReplyViaTopic() throws Exception {
 
-		TextMessage message1 = create(StompCommand.SUBSCRIBE).headers("id:subs1", "destination:/topic/foo").build();
-		TextMessage message2 = create(StompCommand.SEND).headers("destination:/topic/foo").body("5").build();
+		TextMessage m1 = create(StompCommand.SUBSCRIBE).headers("id:subs1", "destination:/topic/foo").build();
+		TextMessage m2 = create(StompCommand.SEND).headers("destination:/topic/foo").body("5").build();
 
-		TestClientWebSocketHandler clientHandler = new TestClientWebSocketHandler(1, message1, message2);
+		TestClientWebSocketHandler clientHandler = new TestClientWebSocketHandler(1, m1, m2);
 		WebSocketSession session = doHandshake(clientHandler, "/ws").get();
 
 		try {
@@ -140,8 +141,8 @@ public class StompWebSocketIntegrationTests extends AbstractWebSocketIntegration
 	@Test
 	public void sendSubscribeToControllerAndReceiveReply() throws Exception {
 
-		TextMessage message = create(StompCommand.SUBSCRIBE).headers(
-				"id:subs1", "destination:/app/number").build();
+		String destHeader = "destination:/app/number";
+		TextMessage message = create(StompCommand.SUBSCRIBE).headers("id:subs1", destHeader).build();
 
 		TestClientWebSocketHandler clientHandler = new TestClientWebSocketHandler(1, message);
 		WebSocketSession session = doHandshake(clientHandler, "/ws").get();
@@ -149,7 +150,7 @@ public class StompWebSocketIntegrationTests extends AbstractWebSocketIntegration
 		try {
 			assertTrue(clientHandler.latch.await(2, TimeUnit.SECONDS));
 			String payload = clientHandler.actual.get(0).getPayload();
-			assertTrue("Expected STOMP destination=/app/number, got " + payload, payload.contains("destination:/app/number"));
+			assertTrue("Expected STOMP destination=/app/number, got " + payload, payload.contains(destHeader));
 			assertTrue("Expected STOMP Payload=42, got " + payload, payload.contains("42"));
 		}
 		finally {
@@ -157,6 +158,29 @@ public class StompWebSocketIntegrationTests extends AbstractWebSocketIntegration
 		}
 	}
 
+	@Test
+	public void handleExceptionAndSendToUser() throws Exception {
+
+		String destHeader = "destination:/user/queue/error";
+		TextMessage m1 = create(StompCommand.SUBSCRIBE).headers("id:subs1", destHeader).build();
+		TextMessage m2 = create(StompCommand.SEND).headers("destination:/app/exception").build();
+
+		TestClientWebSocketHandler clientHandler = new TestClientWebSocketHandler(1, m1, m2);
+		WebSocketSession session = doHandshake(clientHandler, "/ws").get();
+
+		try {
+			assertTrue(clientHandler.latch.await(2, TimeUnit.SECONDS));
+
+			String payload = clientHandler.actual.get(0).getPayload();
+			assertTrue(payload.startsWith("MESSAGE\n"));
+			assertTrue(payload.contains("destination:/user/queue/error\n"));
+			assertTrue(payload.endsWith("\"Got error: Bad input\"\0"));
+		}
+		finally {
+			session.close();
+		}
+	}
+
 
 	@IntegrationTestController
 	static class SimpleController {
@@ -174,10 +198,10 @@ public class StompWebSocketIntegrationTests extends AbstractWebSocketIntegration
 		}
 
 		@MessageExceptionHandler
-		public void handleException(IllegalArgumentException ex) {
-
+		@SendToUser("/queue/error")
+		public String handleException(IllegalArgumentException ex) {
+			return "Got error: " + ex.getMessage();
 		}
-
 	}
 
 	@IntegrationTestController

spring-websocket/src/test/resources/log4j.properties

@@ -5,6 +5,5 @@ log4j.appender.console.layout.ConversionPattern=%d{HH:mm:ss,SSS} [%c] - %m%n
 log4j.rootCategory=WARN, console
 log4j.logger.org.springframework.web=DEBUG
 log4j.logger.org.springframework.web.socket=DEBUG
-
-#log4j.logger.org.springframework.web.socket=TRACE
+log4j.logger.org.springframework.messaging=DEBUG