Introduce GraphQL media type static final

See gh-45487
See gh-45494

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/graphql/servlet/GraphQlWebMvcAutoConfigurationTests.java

@@ -224,8 +224,8 @@ class GraphQlWebMvcAutoConfigurationTests {
 				.content("{\"query\": \"" + query + "\"}"))
 				.satisfies((result) -> assertThat(result).hasStatusOk()
 					.headers()
-					.containsEntry(HttpHeaders.ACCESS_CONTROL_ALLOW_ORIGIN, List.of("https://example.com"))
-					.containsEntry(HttpHeaders.ACCESS_CONTROL_ALLOW_CREDENTIALS, List.of("true")));
+					.hasValue(HttpHeaders.ACCESS_CONTROL_ALLOW_ORIGIN, "https://example.com")
+					.hasValue(HttpHeaders.ACCESS_CONTROL_ALLOW_CREDENTIALS, "true"));
 		});
 	}
 

spring-boot-project/spring-boot-test-autoconfigure/src/main/java/org/springframework/boot/test/autoconfigure/graphql/tester/GraphQlTesterAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2022 the original author or authors.
+ * Copyright 2012-2025 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.
@@ -44,6 +44,8 @@ import org.springframework.http.codec.json.Jackson2JsonEncoder;
 @ConditionalOnClass({ GraphQL.class, GraphQlTester.class })
 public class GraphQlTesterAutoConfiguration {
 
+	private static final MediaType APPLICATION_GRAPHQL = new MediaType("application", "graphql+json");
+
 	@Bean
 	@ConditionalOnBean(ExecutionGraphQlService.class)
 	@ConditionalOnMissingBean
@@ -53,7 +55,7 @@ public class GraphQlTesterAutoConfiguration {
 		ExecutionGraphQlServiceTester.Builder<?> builder = ExecutionGraphQlServiceTester.builder(graphQlService);
 		objectMapperProvider.ifAvailable((objectMapper) -> {
 			builder.encoder(new Jackson2JsonEncoder(objectMapper, MediaType.APPLICATION_GRAPHQL_RESPONSE,
-					MediaType.APPLICATION_JSON, MediaType.APPLICATION_GRAPHQL));
+					MediaType.APPLICATION_JSON, APPLICATION_GRAPHQL));
 			builder.decoder(new Jackson2JsonDecoder(objectMapper, MediaType.APPLICATION_JSON));
 		});
 		return builder.build();