Deprecate use of path extensions for request mapping and content negotiation

Closes gh-20528

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfiguration.java

 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -220,6 +220,7 @@ public class WebMvcAutoConfiguration {
 		}
 
 		@Override
+		@SuppressWarnings("deprecation")
 		public void configurePathMatch(PathMatchConfigurer configurer) {
 			configurer.setUseSuffixPatternMatch(this.mvcProperties.getPathmatch().isUseSuffixPattern());
 			configurer.setUseRegisteredSuffixPatternMatch(
@@ -227,6 +228,7 @@ public class WebMvcAutoConfiguration {
 		}
 
 		@Override
+		@SuppressWarnings("deprecation")
 		public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
 			WebMvcProperties.Contentnegotiation contentnegotiation = this.mvcProperties.getContentnegotiation();
 			configurer.favorPathExtension(contentnegotiation.isFavorPathExtension());

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/servlet/WebMvcProperties.java

 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -22,6 +22,7 @@ import java.util.Locale;
 import java.util.Map;
 
 import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.boot.context.properties.DeprecatedConfigurationProperty;
 import org.springframework.http.MediaType;
 import org.springframework.util.Assert;
 import org.springframework.validation.DefaultMessageCodesResolver;
@@ -352,10 +353,14 @@ public class WebMvcProperties {
 		 */
 		private String parameterName;
 
+		@DeprecatedConfigurationProperty(
+				reason = "Use of path extensions for request mapping and for content negotiation is discouraged.")
+		@Deprecated
 		public boolean isFavorPathExtension() {
 			return this.favorPathExtension;
 		}
 
+		@Deprecated
 		public void setFavorPathExtension(boolean favorPathExtension) {
 			this.favorPathExtension = favorPathExtension;
 		}
@@ -402,18 +407,26 @@ public class WebMvcProperties {
 		 */
 		private boolean useRegisteredSuffixPattern = false;
 
+		@DeprecatedConfigurationProperty(
+				reason = "Use of path extensions for request mapping and for content negotiation is discouraged.")
+		@Deprecated
 		public boolean isUseSuffixPattern() {
 			return this.useSuffixPattern;
 		}
 
+		@Deprecated
 		public void setUseSuffixPattern(boolean useSuffixPattern) {
 			this.useSuffixPattern = useSuffixPattern;
 		}
 
+		@DeprecatedConfigurationProperty(
+				reason = "Use of path extensions for request mapping and for content negotiation is discouraged.")
+		@Deprecated
 		public boolean isUseRegisteredSuffixPattern() {
 			return this.useRegisteredSuffixPattern;
 		}
 
+		@Deprecated
 		public void setUseRegisteredSuffixPattern(boolean useRegisteredSuffixPattern) {
 			this.useRegisteredSuffixPattern = useRegisteredSuffixPattern;
 		}

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfigurationTests.java

 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -432,6 +432,7 @@ class WebMvcAutoConfigurationTests {
 	}
 
 	@Test
+	@Deprecated
 	void customMediaTypes() {
 		this.contextRunner.withPropertyValues("spring.mvc.contentnegotiation.media-types.yaml:text/yaml",
 				"spring.mvc.contentnegotiation.favor-path-extension:true").run((context) -> {
@@ -687,6 +688,7 @@ class WebMvcAutoConfigurationTests {
 	}
 
 	@Test
+	@Deprecated
 	void useSuffixPatternMatch() {
 		this.contextRunner.withPropertyValues("spring.mvc.pathmatch.use-suffix-pattern:true",
 				"spring.mvc.pathmatch.use-registered-suffix-pattern:true").run((context) -> {
@@ -707,6 +709,7 @@ class WebMvcAutoConfigurationTests {
 	}
 
 	@Test
+	@Deprecated
 	void pathExtensionContentNegotiation() {
 		this.contextRunner.withPropertyValues("spring.mvc.contentnegotiation.favor-path-extension:true")
 				.run((context) -> {
@@ -718,6 +721,7 @@ class WebMvcAutoConfigurationTests {
 	}
 
 	@Test
+	@Deprecated
 	void queryParameterContentNegotiation() {
 		this.contextRunner.withPropertyValues("spring.mvc.contentnegotiation.favor-parameter:true").run((context) -> {
 			RequestMappingHandlerMapping handlerMapping = context.getBean(RequestMappingHandlerMapping.class);

spring-boot-project/spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -2211,6 +2211,7 @@ Instead of using suffix matching, we can use a query parameter to ensure that re
 	spring.mvc.contentnegotiation.media-types.markdown=text/markdown
 ----
 
+Suffix pattern matching is deprecated and will be removed in a future release.
 If you understand the caveats and would still like your application to use suffix pattern matching, the following configuration is required:
 
 [source,properties,indent=0,subs="verbatim,quotes,attributes",configprops]