Log unhandled exceptions in WebSocket handlers

Closes gh-1122

Author: rstoyanchev

spring-graphql/src/main/java/org/springframework/graphql/server/webflux/GraphQlWebSocketHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -28,6 +28,8 @@
 import java.util.concurrent.atomic.AtomicReference;
 
 import graphql.ExecutionResult;
+import graphql.GraphQLError;
+import graphql.GraphqlErrorBuilder;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.reactivestreams.Publisher;
@@ -36,6 +38,8 @@
 import reactor.core.publisher.Mono;
 
 import org.springframework.aot.hint.annotation.RegisterReflectionForBinding;
+import org.springframework.graphql.execution.ErrorType;
+import org.springframework.graphql.execution.SubscriptionPublisherException;
 import org.springframework.graphql.server.WebGraphQlHandler;
 import org.springframework.graphql.server.WebGraphQlResponse;
 import org.springframework.graphql.server.WebSocketGraphQlInterceptor;
@@ -256,7 +260,20 @@ private Flux<WebSocketMessage> handleResponse(WebSocketSession session, String i
 						CloseStatus status = new CloseStatus(4409, "Subscriber for " + id + " already exists");
 						return GraphQlStatus.close(session, status);
 					}
-					return Mono.fromCallable(() -> this.codecDelegate.encodeError(session, id, ex));
+					List<GraphQLError> errors;
+					if (ex instanceof SubscriptionPublisherException subscriptionEx) {
+						errors = subscriptionEx.getErrors();
+					}
+					else {
+						if (logger.isErrorEnabled()) {
+							logger.error("Unresolved " + ex.getClass().getSimpleName() + " for request id " + id, ex);
+						}
+						errors = Collections.singletonList(GraphqlErrorBuilder.newError()
+								.message("Subscription error")
+								.errorType(ErrorType.INTERNAL_ERROR)
+								.build());
+					}
+					return Mono.fromCallable(() -> this.codecDelegate.encodeError(session, id, errors));
 				});
 	}
 

spring-graphql/src/main/java/org/springframework/graphql/server/webflux/WebSocketCodecDelegate.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -16,20 +16,16 @@
 
 package org.springframework.graphql.server.webflux;
 
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
 import graphql.GraphQLError;
-import graphql.GraphqlErrorBuilder;
 
 import org.springframework.core.ResolvableType;
 import org.springframework.core.codec.Decoder;
 import org.springframework.core.codec.Encoder;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DataBufferUtils;
-import org.springframework.graphql.execution.ErrorType;
-import org.springframework.graphql.execution.SubscriptionPublisherException;
 import org.springframework.graphql.server.support.GraphQlWebSocketMessage;
 import org.springframework.http.MediaType;
 import org.springframework.http.codec.CodecConfigurer;
@@ -105,13 +101,7 @@ WebSocketMessage encodeNext(WebSocketSession session, String id, Map<String, Obj
 		return encode(session, GraphQlWebSocketMessage.next(id, responseMap));
 	}
 
-	WebSocketMessage encodeError(WebSocketSession session, String id, Throwable ex) {
-		List<GraphQLError> errors = ((ex instanceof SubscriptionPublisherException) ?
-				((SubscriptionPublisherException) ex).getErrors() :
-				Collections.singletonList(GraphqlErrorBuilder.newError()
-						.message("Subscription error")
-						.errorType(ErrorType.INTERNAL_ERROR)
-						.build()));
+	WebSocketMessage encodeError(WebSocketSession session, String id, List<GraphQLError> errors) {
 		return encode(session, GraphQlWebSocketMessage.error(id, errors));
 	}
 

spring-graphql/src/main/java/org/springframework/graphql/server/webmvc/GraphQlWebSocketHandler.java

@@ -347,12 +347,19 @@ private Flux<TextMessage> handleResponse(WebSocketSession session, String id, We
 						GraphQlStatus.closeSession(session, status);
 						return Flux.empty();
 					}
-					List<GraphQLError> errors = ((ex instanceof SubscriptionPublisherException) ?
-							((SubscriptionPublisherException) ex).getErrors() :
-							Collections.singletonList(GraphqlErrorBuilder.newError()
-									.message("Subscription error")
-									.errorType(ErrorType.INTERNAL_ERROR)
-									.build()));
+					List<GraphQLError> errors;
+					if (ex instanceof SubscriptionPublisherException subscriptionEx) {
+						errors = subscriptionEx.getErrors();
+					}
+					else {
+						if (logger.isErrorEnabled()) {
+							logger.error("Unresolved " + ex.getClass().getSimpleName() + " for request id " + id, ex);
+						}
+						errors = Collections.singletonList(GraphqlErrorBuilder.newError()
+								.message("Subscription error")
+								.errorType(ErrorType.INTERNAL_ERROR)
+								.build());
+					}
 					return Mono.just(encode(GraphQlWebSocketMessage.error(id, errors)));
 				});
 	}