Document default value of spring.thymeleaf.reactive.media-types

Closes gh-30280

spring-boot-project/spring-boot-autoconfigure/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -1766,6 +1766,25 @@
       "name": "spring.thymeleaf.prefix",
       "defaultValue": "classpath:/templates/"
     },
+    {
+      "name": "spring.thymeleaf.reactive.media-types",
+      "defaultValue": [
+        "text/html",
+        "application/xhtml+xml",
+        "application/xml",
+        "text/xml",
+        "application/rss+xml",
+        "application/atom+xml",
+        "application/javascript",
+        "application/ecmascript",
+        "text/javascript",
+        "text/ecmascript",
+        "application/json",
+        "text/css",
+        "text/plain",
+        "text/event-stream"
+      ]
+    },
     {
       "name": "spring.thymeleaf.suffix",
       "defaultValue": ".html"

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/thymeleaf/ThymeleafReactiveAutoConfigurationTests.java

@@ -87,11 +87,24 @@ class ThymeleafReactiveAutoConfigurationTests {
 		});
 	}
 
+	@Test
+	void defaultMediaTypes() {
+		this.contextRunner.run(
+				(context) -> assertThat(context.getBean(ThymeleafReactiveViewResolver.class).getSupportedMediaTypes())
+						.containsExactly(MediaType.TEXT_HTML, MediaType.APPLICATION_XHTML_XML,
+								MediaType.APPLICATION_XML, MediaType.TEXT_XML, MediaType.APPLICATION_RSS_XML,
+								MediaType.APPLICATION_ATOM_XML, new MediaType("application", "javascript"),
+								new MediaType("application", "ecmascript"), new MediaType("text", "javascript"),
+								new MediaType("text", "ecmascript"), MediaType.APPLICATION_JSON,
+								new MediaType("text", "css"), MediaType.TEXT_PLAIN, MediaType.TEXT_EVENT_STREAM)
+						.satisfies(System.out::println));
+	}
+
 	@Test
 	void overrideMediaTypes() {
 		this.contextRunner.withPropertyValues("spring.thymeleaf.reactive.media-types:text/html,text/plain").run(
 				(context) -> assertThat(context.getBean(ThymeleafReactiveViewResolver.class).getSupportedMediaTypes())
-						.contains(MediaType.TEXT_HTML, MediaType.TEXT_PLAIN));
+						.containsExactly(MediaType.TEXT_HTML, MediaType.TEXT_PLAIN));
 	}
 
 	@Test