Simplify media files detection in WebMvcConfigurationSupport

Prior to this commit, `WebMvcConfigurationSupport` would configure file
extensions/media types registrations based on classpath detection.
Since gh-33894, the detection of message converters is located in a
single place, `HttpMessageConverters`.

This commit updates the `WebMvcConfigurationSupport` to use the actual
message converters configured to decide which file extensions should be
set up for content negotiation.

See gh-33894

spring-webmvc/src/main/java/org/springframework/web/servlet/config/annotation/WebMvcConfigurationSupport.java

@@ -16,11 +16,14 @@
 
 package org.springframework.web.servlet.config.annotation;
 
+import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
 
 import jakarta.servlet.ServletContext;
 import org.jspecify.annotations.Nullable;
@@ -177,63 +180,19 @@ import org.springframework.web.util.pattern.PathPatternParser;
  */
 public class WebMvcConfigurationSupport implements ApplicationContextAware, ServletContextAware {
 
-	private static final boolean romePresent;
-
-	private static final boolean jaxb2Present;
-
 	private static final boolean jacksonPresent;
 
 	private static final boolean jackson2Present;
 
-	private static final boolean jacksonXmlPresent;
-
-	private static final boolean jackson2XmlPresent;
-
-	private static final boolean jacksonSmilePresent;
-
-	private static final boolean jackson2SmilePresent;
-
-	private static final boolean jacksonCborPresent;
-
-	private static final boolean jackson2CborPresent;
-
-	private static final boolean jacksonYamlPresent;
-
-	private static final boolean jackson2YamlPresent;
-
-	private static final boolean gsonPresent;
-
-	private static final boolean jsonbPresent;
-
 	private static final boolean kotlinSerializationPresent;
 
-	private static final boolean kotlinSerializationCborPresent;
-
-	private static final boolean kotlinSerializationJsonPresent;
-
-	private static final boolean kotlinSerializationProtobufPresent;
 
 	static {
 		ClassLoader classLoader = WebMvcConfigurationSupport.class.getClassLoader();
-		romePresent = ClassUtils.isPresent("com.rometools.rome.feed.WireFeed", classLoader);
-		jaxb2Present = ClassUtils.isPresent("jakarta.xml.bind.Binder", classLoader);
 		jacksonPresent = ClassUtils.isPresent("tools.jackson.databind.ObjectMapper", classLoader);
 		jackson2Present = ClassUtils.isPresent("com.fasterxml.jackson.databind.ObjectMapper", classLoader) &&
 				ClassUtils.isPresent("com.fasterxml.jackson.core.JsonGenerator", classLoader);
-		jacksonXmlPresent = jacksonPresent && ClassUtils.isPresent("tools.jackson.dataformat.xml.XmlMapper", classLoader);
-		jackson2XmlPresent = jackson2Present && ClassUtils.isPresent("com.fasterxml.jackson.dataformat.xml.XmlMapper", classLoader);
-		jacksonSmilePresent = jacksonPresent && ClassUtils.isPresent("tools.jackson.dataformat.smile.SmileMapper", classLoader);
-		jackson2SmilePresent = jackson2Present && ClassUtils.isPresent("com.fasterxml.jackson.dataformat.smile.SmileFactory", classLoader);
-		jacksonCborPresent = jacksonPresent && ClassUtils.isPresent("tools.jackson.dataformat.cbor.CBORMapper", classLoader);
-		jackson2CborPresent = jackson2Present && ClassUtils.isPresent("com.fasterxml.jackson.dataformat.cbor.CBORFactory", classLoader);
-		jacksonYamlPresent = jacksonPresent && ClassUtils.isPresent("tools.jackson.dataformat.yaml.YAMLMapper", classLoader);
-		jackson2YamlPresent = jackson2Present && ClassUtils.isPresent("com.fasterxml.jackson.dataformat.yaml.YAMLFactory", classLoader);
-		gsonPresent = ClassUtils.isPresent("com.google.gson.Gson", classLoader);
-		jsonbPresent = ClassUtils.isPresent("jakarta.json.bind.Jsonb", classLoader);
 		kotlinSerializationPresent = ClassUtils.isPresent("kotlinx.serialization.Serializable", classLoader);
-		kotlinSerializationCborPresent = kotlinSerializationPresent && ClassUtils.isPresent("kotlinx.serialization.cbor.Cbor", classLoader);
-		kotlinSerializationJsonPresent = kotlinSerializationPresent && ClassUtils.isPresent("kotlinx.serialization.json.Json", classLoader);
-		kotlinSerializationProtobufPresent = kotlinSerializationPresent && ClassUtils.isPresent("kotlinx.serialization.protobuf.ProtoBuf", classLoader);
 	}
 
 
@@ -444,23 +403,32 @@ public class WebMvcConfigurationSupport implements ApplicationContextAware, Serv
 
 	protected Map<String, MediaType> getDefaultMediaTypes() {
 		Map<String, MediaType> map = new HashMap<>(4);
-		if (romePresent) {
+		List<HttpMessageConverter<?>> messageConverters = getMessageConverters();
+		Set<MediaType> supportedMediaTypes = messageConverters.stream()
+				.flatMap(converter -> converter.getSupportedMediaTypes().stream())
+				.collect(Collectors.toSet());
+		if (supportedMediaTypes.contains(MediaType.APPLICATION_ATOM_XML)) {
 			map.put("atom", MediaType.APPLICATION_ATOM_XML);
+		}
+		if (supportedMediaTypes.contains(MediaType.APPLICATION_RSS_XML)) {
 			map.put("rss", MediaType.APPLICATION_RSS_XML);
 		}
-		if (jaxb2Present || jacksonXmlPresent || jackson2XmlPresent) {
+		MediaType xmlUtf8MediaType = new MediaType("application", "xml", StandardCharsets.UTF_8);
+		if (supportedMediaTypes.contains(MediaType.APPLICATION_XML) ||
+				supportedMediaTypes.contains(xmlUtf8MediaType)) {
 			map.put("xml", MediaType.APPLICATION_XML);
 		}
-		if (jacksonPresent || jackson2Present || gsonPresent || jsonbPresent || kotlinSerializationJsonPresent) {
+		if (supportedMediaTypes.contains(MediaType.APPLICATION_JSON)) {
 			map.put("json", MediaType.APPLICATION_JSON);
 		}
-		if (jacksonSmilePresent || jackson2SmilePresent) {
-			map.put("smile", MediaType.valueOf("application/x-jackson-smile"));
+		MediaType smileMediaType = new MediaType("application", "x-jackson-smile");
+		if (supportedMediaTypes.contains(smileMediaType)) {
+			map.put("smile", smileMediaType);
 		}
-		if (jacksonCborPresent || jackson2CborPresent || kotlinSerializationCborPresent) {
+		if (supportedMediaTypes.contains(MediaType.APPLICATION_CBOR)) {
 			map.put("cbor", MediaType.APPLICATION_CBOR);
 		}
-		if (jacksonYamlPresent || jackson2YamlPresent) {
+		if (supportedMediaTypes.contains(MediaType.APPLICATION_ATOM_XML)) {
 			map.put("yaml", MediaType.APPLICATION_YAML);
 		}
 		return map;

spring-webmvc/src/test/java/org/springframework/web/servlet/config/annotation/WebMvcConfigurationSupportExtensionTests.java

@@ -91,7 +91,6 @@ import org.springframework.web.util.UrlPathHelper;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.Mockito.mock;
 import static org.springframework.http.MediaType.APPLICATION_JSON;
-import static org.springframework.http.MediaType.APPLICATION_XML;
 
 /**
  * A test fixture with a subclass of {@link WebMvcConfigurationSupport} that also
@@ -276,9 +275,6 @@ class WebMvcConfigurationSupportExtensionTests {
 		ContentNegotiationManager manager = mapping.getContentNegotiationManager();
 		assertThat(manager.resolveMediaTypes(webRequest)).isEqualTo(Collections.singletonList(APPLICATION_JSON));
 
-		request.setParameter("f", "xml");
-		assertThat(manager.resolveMediaTypes(webRequest)).isEqualTo(Collections.singletonList(APPLICATION_XML));
-
 		SimpleUrlHandlerMapping handlerMapping = (SimpleUrlHandlerMapping) this.config.resourceHandlerMapping(
 				this.config.mvcContentNegotiationManager(), this.config.mvcConversionService(),
 				this.config.mvcResourceUrlProvider());

spring-webmvc/src/test/java/org/springframework/web/servlet/config/annotation/WebMvcConfigurationSupportTests.java

@@ -45,6 +45,7 @@ import org.springframework.format.annotation.DateTimeFormat.ISO;
 import org.springframework.format.support.FormattingConversionService;
 import org.springframework.http.HttpEntity;
 import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
 import org.springframework.http.converter.AbstractJacksonHttpMessageConverter;
 import org.springframework.http.converter.HttpMessageConverter;
 import org.springframework.http.converter.xml.JacksonXmlHttpMessageConverter;
@@ -53,6 +54,7 @@ import org.springframework.util.AntPathMatcher;
 import org.springframework.util.PathMatcher;
 import org.springframework.validation.Validator;
 import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;
+import org.springframework.web.accept.ContentNegotiationManager;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.ResponseStatus;
@@ -213,6 +215,23 @@ class WebMvcConfigurationSupportTests {
 		assertThat(bodyAdvice.get(3).getClass()).isEqualTo(KotlinResponseBodyAdvice.class);
 	}
 
+	@Test
+	void contentNegotiationManager() {
+		ApplicationContext context = initContext(WebConfig.class);
+		ContentNegotiationManager contentNegotiation = context.getBean(ContentNegotiationManager.class);
+		Map<String, MediaType> mediaTypeMappings = contentNegotiation.getMediaTypeMappings();
+
+		assertThat(mediaTypeMappings)
+				.containsEntry("atom", MediaType.APPLICATION_ATOM_XML)
+				.containsEntry("rss", MediaType.APPLICATION_RSS_XML)
+				.containsEntry("rss", MediaType.APPLICATION_RSS_XML)
+				.containsEntry("xml", MediaType.APPLICATION_XML)
+				.containsEntry("json", MediaType.APPLICATION_JSON)
+				.containsEntry("smile", MediaType.valueOf("application/x-jackson-smile"))
+				.containsEntry("cbor", MediaType.APPLICATION_CBOR)
+				.containsEntry("yaml", MediaType.APPLICATION_YAML);
+	}
+
 	@Test
 	void uriComponentsContributor() {
 		ApplicationContext context = initContext(WebConfig.class);