Polishing in GraphQlHttpHandler

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

@@ -76,14 +76,15 @@ public Mono<ServerResponse> handleRequest(ServerRequest request) {
 		return readRequest(request)
 				.flatMap((body) -> {
 					WebGraphQlRequest graphQlRequest = new WebGraphQlRequest(
-							request.uri(), request.headers().asHttpHeaders(),
-							request.cookies(), request.remoteAddress().orElse(null),
-							request.attributes(), body,
+							request.uri(), request.headers().asHttpHeaders(), request.cookies(),
+							request.remoteAddress().orElse(null), request.attributes(), body,
 							request.exchange().getRequest().getId(),
 							request.exchange().getLocaleContext().getLocale());
+
 					if (this.logger.isDebugEnabled()) {
 						this.logger.debug("Executing: " + graphQlRequest);
 					}
+
 					return this.graphQlHandler.handleRequest(graphQlRequest);
 				})
 				.flatMap((response) -> {
@@ -92,6 +93,7 @@ public Mono<ServerResponse> handleRequest(ServerRequest request) {
 						this.logger.debug("Execution result " +
 								(!CollectionUtils.isEmpty(errors) ? "has errors: " + errors : "is ready") + ".");
 					}
+
 					return prepareResponse(request, response);
 				});
 	}

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

@@ -18,9 +18,12 @@
 
 import java.io.IOException;
 import java.util.List;
+import java.util.Map;
 
 import jakarta.servlet.ServletException;
 import jakarta.servlet.http.Cookie;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import reactor.core.publisher.Mono;
@@ -36,7 +39,9 @@
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.http.server.ServerHttpRequest;
 import org.springframework.http.server.ServletServerHttpRequest;
+import org.springframework.http.server.ServletServerHttpResponse;
 import org.springframework.lang.Nullable;
 import org.springframework.util.AlternativeJdkIdGenerator;
 import org.springframework.util.Assert;
@@ -46,6 +51,7 @@
 import org.springframework.util.MultiValueMap;
 import org.springframework.web.HttpMediaTypeNotSupportedException;
 import org.springframework.web.server.ServerWebInputException;
+import org.springframework.web.servlet.ModelAndView;
 import org.springframework.web.servlet.function.ServerRequest;
 import org.springframework.web.servlet.function.ServerResponse;
 
@@ -79,11 +85,19 @@ protected AbstractGraphQlHttpHandler(
 
 
 	/**
-	 * Return the custom message converter, if configured, to read and write with.
+	 * Exposes a {@link ServerResponse.HeadersBuilder.WriteFunction} that writes
+	 * with the {@code HttpMessageConverter} provided to the constructor.
+	 * @param resultMap the result map to write
+	 * @param contentType to set the response content type to
+	 * @return the write function, or {@code null} if a
+	 * {@code HttpMessageConverter} was not provided to the constructor
 	 */
 	@Nullable
-	public HttpMessageConverter<Object> getMessageConverter() {
-		return this.messageConverter;
+	protected ServerResponse.HeadersBuilder.WriteFunction getWriteFunction(
+			Map<String, Object> resultMap, MediaType contentType) {
+
+		return (this.messageConverter != null) ?
+				new MessageConverterWriteFunction(resultMap, contentType, this.messageConverter) : null;
 	}
 
 
@@ -133,8 +147,8 @@ private GraphQlRequest readBody(ServerRequest request) throws ServletException {
 			if (this.messageConverter != null) {
 				MediaType contentType = request.headers().contentType().orElse(MediaType.APPLICATION_JSON);
 				if (this.messageConverter.canRead(SerializableGraphQlRequest.class, contentType)) {
-					return (GraphQlRequest) this.messageConverter.read(SerializableGraphQlRequest.class,
-							new ServletServerHttpRequest(request.servletRequest()));
+					ServerHttpRequest httpRequest = new ServletServerHttpRequest(request.servletRequest());
+					return (GraphQlRequest) this.messageConverter.read(SerializableGraphQlRequest.class, httpRequest);
 				}
 				throw new HttpMediaTypeNotSupportedException(
 						contentType, this.messageConverter.getSupportedMediaTypes(), request.method());
@@ -181,4 +195,20 @@ private static SerializableGraphQlRequest applyApplicationGraphQlFallback(
 	protected abstract ServerResponse prepareResponse(
 			ServerRequest request, Mono<WebGraphQlResponse> responseMono) throws ServletException;
 
+
+	/**
+	 * WriteFunction that writes with a given, fixed {@link HttpMessageConverter}.
+	 */
+	private record MessageConverterWriteFunction(
+			Map<String, Object> resultMap, MediaType contentType, HttpMessageConverter<Object> converter)
+			implements ServerResponse.HeadersBuilder.WriteFunction {
+
+		@Override
+		public ModelAndView write(HttpServletRequest request, HttpServletResponse response) throws Exception {
+			ServletServerHttpResponse httpResponse = new ServletServerHttpResponse(response);
+			this.converter.write(this.resultMap, this.contentType, httpResponse);
+			return null;
+		}
+	}
+
 }

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

@@ -27,7 +27,6 @@
 import org.springframework.graphql.server.WebGraphQlResponse;
 import org.springframework.http.MediaType;
 import org.springframework.http.converter.HttpMessageConverter;
-import org.springframework.http.server.ServletServerHttpResponse;
 import org.springframework.lang.Nullable;
 import org.springframework.web.servlet.function.ServerRequest;
 import org.springframework.web.servlet.function.ServerResponse;
@@ -56,12 +55,12 @@ public GraphQlHttpHandler(WebGraphQlHandler graphQlHandler) {
 	}
 
 	/**
-	 * Create a new instance with a custom message converter.
-	 * <p>If no converter is provided, this will use
+	 * Create a new instance with a custom message converter for GraphQL payloads.
+	 * <p>If no converter is provided, the handler will use
 	 * {@link org.springframework.web.servlet.config.annotation.WebMvcConfigurer#configureMessageConverters(List)
-	 * the one configured in the web framework}.
+	 * the one configured for web use}.
 	 * @param graphQlHandler common handler for GraphQL over HTTP requests
-	 * @param converter custom {@link HttpMessageConverter} to read and write GraphQL payloads
+	 * @param converter the converter to use to read and write GraphQL payloads
 	 */
 	public GraphQlHttpHandler(WebGraphQlHandler graphQlHandler, @Nullable HttpMessageConverter<?> converter) {
 		super(graphQlHandler, converter);
@@ -77,15 +76,12 @@ protected ServerResponse prepareResponse(ServerRequest request, Mono<WebGraphQlR
 			builder.headers((headers) -> headers.putAll(response.getResponseHeaders()));
 			builder.contentType(contentType);
 
-			if (getMessageConverter() != null) {
-				return builder.build(writeFunction(getMessageConverter(), contentType, response.toMap()));
-			}
-			else {
-				return builder.body(response.toMap());
-			}
+			Map<String, Object> resultMap = response.toMap();
+			ServerResponse.HeadersBuilder.WriteFunction writer = getWriteFunction(resultMap, contentType);
+			return (writer != null) ? builder.build(writer) : builder.body(resultMap);
 		}).toFuture();
 
-		// This won't be needed with a Spring Framework 6.2 baseline:
+		// This won't be needed on a Spring Framework 6.2 baseline:
 		// https://github.com/spring-projects/spring-framework/issues/32223
 
 		if (future.isDone() && !future.isCancelled() && !future.isCompletedExceptionally()) {
@@ -100,23 +96,13 @@ protected ServerResponse prepareResponse(ServerRequest request, Mono<WebGraphQlR
 		return ServerResponse.async(future);
 	}
 
-	private static MediaType selectResponseMediaType(ServerRequest serverRequest) {
-		for (MediaType accepted : serverRequest.headers().accept()) {
-			if (SUPPORTED_MEDIA_TYPES.contains(accepted)) {
-				return accepted;
+	private static MediaType selectResponseMediaType(ServerRequest request) {
+		for (MediaType mediaType : request.headers().accept()) {
+			if (SUPPORTED_MEDIA_TYPES.contains(mediaType)) {
+				return mediaType;
 			}
 		}
 		return MediaType.APPLICATION_JSON;
 	}
 
-	private static ServerResponse.HeadersBuilder.WriteFunction writeFunction(
-			HttpMessageConverter<Object> converter, MediaType contentType, Map<String, Object> resultMap) {
-
-		return (servletRequest, servletResponse) -> {
-			ServletServerHttpResponse httpResponse = new ServletServerHttpResponse(servletResponse);
-			converter.write(resultMap, contentType, httpResponse);
-			return null;
-		};
-	}
-
 }