Add property for media types of reactive Mustache views

Closes gh-28858

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mustache/MustacheProperties.java

@@ -18,9 +18,11 @@
 
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
+import java.util.List;
 
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.boot.context.properties.DeprecatedConfigurationProperty;
+import org.springframework.http.MediaType;
 import org.springframework.util.MimeType;
 
 /**
@@ -42,6 +44,8 @@ public class MustacheProperties {
 
 	private final Servlet servlet = new Servlet();
 
+	private final Reactive reactive = new Reactive();
+
 	/**
 	 * View names that can be resolved.
 	 */
@@ -81,6 +85,10 @@ public Servlet getServlet() {
 		return this.servlet;
 	}
 
+	public Reactive getReactive() {
+		return this.reactive;
+	}
+
 	public String getPrefix() {
 		return this.prefix;
 	}
@@ -318,4 +326,21 @@ public void setExposeSpringMacroHelpers(boolean exposeSpringMacroHelpers) {
 
 	}
 
+	public static class Reactive {
+
+		/**
+		 * Media types supported by Mustache views.
+		 */
+		private List<MediaType> mediaTypes;
+
+		public List<MediaType> getMediaTypes() {
+			return this.mediaTypes;
+		}
+
+		public void setMediaTypes(List<MediaType> mediaTypes) {
+			this.mediaTypes = mediaTypes;
+		}
+
+	}
+
 }

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mustache/MustacheReactiveWebConfiguration.java

@@ -22,6 +22,7 @@
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication.Type;
+import org.springframework.boot.context.properties.PropertyMapper;
 import org.springframework.boot.web.reactive.result.view.MustacheViewResolver;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -36,11 +37,13 @@ class MustacheReactiveWebConfiguration {
 	@ConditionalOnProperty(prefix = "spring.mustache", name = "enabled", matchIfMissing = true)
 	MustacheViewResolver mustacheViewResolver(Compiler mustacheCompiler, MustacheProperties mustache) {
 		MustacheViewResolver resolver = new MustacheViewResolver(mustacheCompiler);
-		resolver.setPrefix(mustache.getPrefix());
-		resolver.setSuffix(mustache.getSuffix());
-		resolver.setViewNames(mustache.getViewNames());
-		resolver.setRequestContextAttribute(mustache.getRequestContextAttribute());
-		resolver.setCharset(mustache.getCharsetName());
+		PropertyMapper map = PropertyMapper.get().alwaysApplyingWhenNonNull();
+		map.from(mustache::getPrefix).to(resolver::setPrefix);
+		map.from(mustache::getSuffix).to(resolver::setSuffix);
+		map.from(mustache::getViewNames).to(resolver::setViewNames);
+		map.from(mustache::getRequestContextAttribute).to(resolver::setRequestContextAttribute);
+		map.from(mustache::getCharsetName).to(resolver::setCharset);
+		map.from(mustache.getReactive()::getMediaTypes).to(resolver::setSupportedMediaTypes);
 		resolver.setOrder(Ordered.LOWEST_PRECEDENCE - 10);
 		return resolver;
 	}

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

@@ -1627,6 +1627,10 @@
       "name": "spring.mustache.prefix",
       "defaultValue": "classpath:/templates/"
     },
+    {
+      "name": "spring.mustache.reactive.media-types",
+      "defaultValue": "text/html;charset=UTF-8"
+    },
     {
       "name": "spring.mustache.suffix",
       "defaultValue": ".mustache"

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mustache/MustacheAutoConfigurationTests.java

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.autoconfigure.mustache;
 
+import java.util.Arrays;
 import java.util.function.Supplier;
 
 import com.samskivert.mustache.Mustache;
@@ -31,6 +32,7 @@
 import org.springframework.boot.web.servlet.view.MustacheViewResolver;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.http.MediaType;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -133,6 +135,8 @@ void defaultReactiveViewResolverConfiguration() {
 			assertThat(viewResolver).extracting("prefix").isEqualTo("classpath:/templates/");
 			assertThat(viewResolver).extracting("requestContextAttribute").isNull();
 			assertThat(viewResolver).extracting("suffix").isEqualTo(".mustache");
+			assertThat(viewResolver.getSupportedMediaTypes())
+					.containsExactly(MediaType.parseMediaType("text/html;charset=UTF-8"));
 		});
 	}
 
@@ -238,6 +242,14 @@ void suffixCanBeCustomizedOnViewResolver(ViewResolverKind kind) {
 		assertViewResolverProperty(kind, "spring.mustache.suffix=.tache", "suffix", ".tache");
 	}
 
+	@Test
+	void mediaTypesCanBeCustomizedOnReactiveViewResolver() {
+		assertViewResolverProperty(ViewResolverKind.REACTIVE,
+				"spring.mustache.reactive.media-types=text/xml;charset=UTF-8,text/plain;charset=UTF-16", "mediaTypes",
+				Arrays.asList(MediaType.parseMediaType("text/xml;charset=UTF-8"),
+						MediaType.parseMediaType("text/plain;charset=UTF-16")));
+	}
+
 	private void assertViewResolverProperty(ViewResolverKind kind, String property, String field,
 			Object expectedValue) {
 		kind.runner().withConfiguration(AutoConfigurations.of(MustacheAutoConfiguration.class))