Provide config properties for configuring WebFlux's locale resolution

Previously, the locale context resolver used with WebFlux could only be
configured by provided a custom LocaleContextResolver bean. By
constrast, when using Spring MVC, the spring.mvc.locale and
spring.mvc.locale-resolver properties could be used to configure the
locale and the resolver (fixed or Accept header) respectively.

This commit introduces spring.web.locale and spring.web.locale-resolver
properties and deprecates their spring.mvc equivalents. The new
properties can be used to configure locale resolution with either
Spring MVC or WebFlux.

Closes gh-23449

buildSrc/src/main/java/org/springframework/boot/build/context/properties/DocumentConfigurationProperties.java

@@ -72,7 +72,7 @@ public class DocumentConfigurationProperties extends DefaultTask {
 				.addSection("mail").withKeyPrefixes("spring.mail", "spring.sendgrid").addSection("cache")
 				.withKeyPrefixes("spring.cache").addSection("server").withKeyPrefixes("server").addSection("web")
 				.withKeyPrefixes("spring.hateoas", "spring.http", "spring.servlet", "spring.jersey", "spring.mvc",
-						"spring.resources", "spring.webflux")
+						"spring.resources", "spring.web", "spring.webflux")
 				.addSection("json").withKeyPrefixes("spring.jackson", "spring.gson").addSection("rsocket")
 				.withKeyPrefixes("spring.rsocket").addSection("templating")
 				.withKeyPrefixes("spring.freemarker", "spring.groovy", "spring.mustache", "spring.thymeleaf")

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

+/*
+ * 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.autoconfigure.web;
+
+import java.util.Locale;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+
+/**
+ * {@link ConfigurationProperties Configuration properties} for general web concerns.
+ *
+ * @author Andy Wilkinson
+ * @since 2.4.0
+ */
+@ConfigurationProperties("spring.web")
+public class WebProperties {
+
+	/**
+	 * Locale to use. By default, this locale is overridden by the "Accept-Language"
+	 * header.
+	 */
+	private Locale locale;
+
+	/**
+	 * Define how the locale should be resolved.
+	 */
+	private LocaleResolver localeResolver = LocaleResolver.ACCEPT_HEADER;
+
+	public Locale getLocale() {
+		return this.locale;
+	}
+
+	public void setLocale(Locale locale) {
+		this.locale = locale;
+	}
+
+	public LocaleResolver getLocaleResolver() {
+		return this.localeResolver;
+	}
+
+	public void setLocaleResolver(LocaleResolver localeResolver) {
+		this.localeResolver = localeResolver;
+	}
+
+	public enum LocaleResolver {
+
+		/**
+		 * Always use the configured locale.
+		 */
+		FIXED,
+
+		/**
+		 * Use the "Accept-Language" header or the configured locale if the header is not
+		 * set.
+		 */
+		ACCEPT_HEADER
+
+	}
+
+}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/reactive/WebFluxAutoConfiguration.java

@@ -36,6 +36,7 @@ import org.springframework.boot.autoconfigure.validation.ValidationAutoConfigura
 import org.springframework.boot.autoconfigure.validation.ValidatorAdapter;
 import org.springframework.boot.autoconfigure.web.ConditionalOnEnabledResourceChain;
 import org.springframework.boot.autoconfigure.web.ResourceProperties;
+import org.springframework.boot.autoconfigure.web.WebProperties;
 import org.springframework.boot.autoconfigure.web.format.DateTimeFormatters;
 import org.springframework.boot.autoconfigure.web.format.WebConversionService;
 import org.springframework.boot.autoconfigure.web.reactive.WebFluxProperties.Format;
@@ -69,6 +70,8 @@ import org.springframework.web.reactive.result.method.annotation.ArgumentResolve
 import org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerAdapter;
 import org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerMapping;
 import org.springframework.web.reactive.result.view.ViewResolver;
+import org.springframework.web.server.i18n.AcceptHeaderLocaleContextResolver;
+import org.springframework.web.server.i18n.FixedLocaleContextResolver;
 import org.springframework.web.server.i18n.LocaleContextResolver;
 
 /**
@@ -216,15 +219,19 @@ public class WebFluxAutoConfiguration {
 	 * Configuration equivalent to {@code @EnableWebFlux}.
 	 */
 	@Configuration(proxyBeanMethods = false)
+	@EnableConfigurationProperties(WebProperties.class)
 	public static class EnableWebFluxConfiguration extends DelegatingWebFluxConfiguration {
 
 		private final WebFluxProperties webFluxProperties;
 
+		private final WebProperties webProperties;
+
 		private final WebFluxRegistrations webFluxRegistrations;
 
-		public EnableWebFluxConfiguration(WebFluxProperties webFluxProperties,
+		public EnableWebFluxConfiguration(WebFluxProperties webFluxProperties, WebProperties webProperties,
 				ObjectProvider<WebFluxRegistrations> webFluxRegistrations) {
 			this.webFluxProperties = webFluxProperties;
+			this.webProperties = webProperties;
 			this.webFluxRegistrations = webFluxRegistrations.getIfUnique();
 		}
 
@@ -269,7 +276,12 @@ public class WebFluxAutoConfiguration {
 		@Override
 		@ConditionalOnMissingBean
 		public LocaleContextResolver localeContextResolver() {
-			return super.localeContextResolver();
+			if (this.webProperties.getLocaleResolver() == WebProperties.LocaleResolver.FIXED) {
+				return new FixedLocaleContextResolver(this.webProperties.getLocale());
+			}
+			AcceptHeaderLocaleContextResolver localeContextResolver = new AcceptHeaderLocaleContextResolver();
+			localeContextResolver.setDefaultLocale(this.webProperties.getLocale());
+			return localeContextResolver;
 		}
 
 	}

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

@@ -20,6 +20,7 @@ import java.time.Duration;
 import java.util.Arrays;
 import java.util.List;
 import java.util.ListIterator;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Optional;
 
@@ -51,6 +52,7 @@ import org.springframework.boot.autoconfigure.validation.ValidatorAdapter;
 import org.springframework.boot.autoconfigure.web.ConditionalOnEnabledResourceChain;
 import org.springframework.boot.autoconfigure.web.ResourceProperties;
 import org.springframework.boot.autoconfigure.web.ResourceProperties.Strategy;
+import org.springframework.boot.autoconfigure.web.WebProperties;
 import org.springframework.boot.autoconfigure.web.format.DateTimeFormatters;
 import org.springframework.boot.autoconfigure.web.format.WebConversionService;
 import org.springframework.boot.autoconfigure.web.servlet.WebMvcProperties.Format;
@@ -358,23 +360,27 @@ public class WebMvcAutoConfiguration {
 	 * Configuration equivalent to {@code @EnableWebMvc}.
 	 */
 	@Configuration(proxyBeanMethods = false)
+	@EnableConfigurationProperties(WebProperties.class)
 	public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration implements ResourceLoaderAware {
 
 		private final ResourceProperties resourceProperties;
 
 		private final WebMvcProperties mvcProperties;
 
+		private final WebProperties webProperties;
+
 		private final ListableBeanFactory beanFactory;
 
 		private final WebMvcRegistrations mvcRegistrations;
 
 		private ResourceLoader resourceLoader;
 
-		public EnableWebMvcConfiguration(ResourceProperties resourceProperties,
-				ObjectProvider<WebMvcProperties> mvcPropertiesProvider,
-				ObjectProvider<WebMvcRegistrations> mvcRegistrationsProvider, ListableBeanFactory beanFactory) {
+		public EnableWebMvcConfiguration(ResourceProperties resourceProperties, WebMvcProperties mvcProperties,
+				WebProperties webProperties, ObjectProvider<WebMvcRegistrations> mvcRegistrationsProvider,
+				ListableBeanFactory beanFactory) {
 			this.resourceProperties = resourceProperties;
-			this.mvcProperties = mvcPropertiesProvider.getIfAvailable();
+			this.mvcProperties = mvcProperties;
+			this.webProperties = webProperties;
 			this.mvcRegistrations = mvcRegistrationsProvider.getIfUnique();
 			this.beanFactory = beanFactory;
 		}
@@ -426,13 +432,18 @@ public class WebMvcAutoConfiguration {
 		@Override
 		@Bean
 		@ConditionalOnMissingBean
-		@ConditionalOnProperty(prefix = "spring.mvc", name = "locale", matchIfMissing = true)
+		@SuppressWarnings("deprecation")
 		public LocaleResolver localeResolver() {
+			if (this.webProperties.getLocaleResolver() == WebProperties.LocaleResolver.FIXED) {
+				return new FixedLocaleResolver(this.webProperties.getLocale());
+			}
 			if (this.mvcProperties.getLocaleResolver() == WebMvcProperties.LocaleResolver.FIXED) {
 				return new FixedLocaleResolver(this.mvcProperties.getLocale());
 			}
 			AcceptHeaderLocaleResolver localeResolver = new AcceptHeaderLocaleResolver();
-			localeResolver.setDefaultLocale(this.mvcProperties.getLocale());
+			Locale locale = (this.webProperties.getLocale() != null) ? this.webProperties.getLocale()
+					: this.mvcProperties.getLocale();
+			localeResolver.setDefaultLocale(locale);
 			return localeResolver;
 		}
 

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

@@ -121,6 +121,8 @@ public class WebMvcProperties {
 		this.messageCodesResolverFormat = messageCodesResolverFormat;
 	}
 
+	@Deprecated
+	@DeprecatedConfigurationProperty(replacement = "spring.web.locale")
 	public Locale getLocale() {
 		return this.locale;
 	}
@@ -129,6 +131,8 @@ public class WebMvcProperties {
 		this.locale = locale;
 	}
 
+	@Deprecated
+	@DeprecatedConfigurationProperty(replacement = "spring.web.locale-resolver")
 	public LocaleResolver getLocaleResolver() {
 		return this.localeResolver;
 	}
@@ -543,6 +547,12 @@ public class WebMvcProperties {
 
 	}
 
+	/**
+	 * Locale resolution options.
+	 * @deprecated since 2.4.0 in favor of
+	 * {@link org.springframework.boot.autoconfigure.web.WebProperties.LocaleResolver}
+	 */
+	@Deprecated
 	public enum LocaleResolver {
 
 		/**

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/reactive/WebFluxAutoConfigurationTests.java

@@ -44,6 +44,7 @@ import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
+import org.springframework.context.i18n.LocaleContext;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.Order;
 import org.springframework.core.convert.ConversionService;
@@ -54,7 +55,10 @@ import org.springframework.format.support.FormattingConversionService;
 import org.springframework.http.CacheControl;
 import org.springframework.http.codec.ServerCodecConfigurer;
 import org.springframework.http.server.reactive.HttpHandler;
+import org.springframework.mock.http.server.reactive.MockServerHttpRequest;
+import org.springframework.mock.web.server.MockServerWebExchange;
 import org.springframework.test.util.ReflectionTestUtils;
+import org.springframework.util.StringUtils;
 import org.springframework.validation.Validator;
 import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;
 import org.springframework.web.filter.reactive.HiddenHttpMethodFilter;
@@ -74,6 +78,7 @@ import org.springframework.web.reactive.result.method.annotation.RequestMappingH
 import org.springframework.web.reactive.result.view.ViewResolutionResultHandler;
 import org.springframework.web.reactive.result.view.ViewResolver;
 import org.springframework.web.server.i18n.AcceptHeaderLocaleContextResolver;
+import org.springframework.web.server.i18n.FixedLocaleContextResolver;
 import org.springframework.web.server.i18n.LocaleContextResolver;
 import org.springframework.web.util.pattern.PathPattern;
 
@@ -454,6 +459,54 @@ class WebFluxAutoConfigurationTests {
 				});
 	}
 
+	@Test
+	void defaultLocaleContextResolver() {
+		this.contextRunner.run((context) -> {
+			assertThat(context).hasSingleBean(LocaleContextResolver.class);
+			LocaleContextResolver resolver = context.getBean(LocaleContextResolver.class);
+			assertThat(((AcceptHeaderLocaleContextResolver) resolver).getDefaultLocale()).isNull();
+		});
+	}
+
+	@Test
+	void whenFixedLocalContextResolverIsUsedThenAcceptLanguagesHeaderIsIgnored() {
+		this.contextRunner.withPropertyValues("spring.web.locale:en_UK", "spring.web.locale-resolver=fixed")
+				.run((context) -> {
+					MockServerHttpRequest request = MockServerHttpRequest.get("/")
+							.acceptLanguageAsLocales(StringUtils.parseLocaleString("nl_NL")).build();
+					MockServerWebExchange exchange = MockServerWebExchange.from(request);
+					LocaleContextResolver localeContextResolver = context.getBean(LocaleContextResolver.class);
+					assertThat(localeContextResolver).isInstanceOf(FixedLocaleContextResolver.class);
+					LocaleContext localeContext = localeContextResolver.resolveLocaleContext(exchange);
+					assertThat(localeContext.getLocale()).isEqualTo(StringUtils.parseLocaleString("en_UK"));
+				});
+	}
+
+	@Test
+	void whenAcceptHeaderLocaleContextResolverIsUsedThenAcceptLanguagesHeaderIsHonoured() {
+		this.contextRunner.withPropertyValues("spring.web.locale:en_UK").run((context) -> {
+			MockServerHttpRequest request = MockServerHttpRequest.get("/")
+					.acceptLanguageAsLocales(StringUtils.parseLocaleString("nl_NL")).build();
+			MockServerWebExchange exchange = MockServerWebExchange.from(request);
+			LocaleContextResolver localeContextResolver = context.getBean(LocaleContextResolver.class);
+			assertThat(localeContextResolver).isInstanceOf(AcceptHeaderLocaleContextResolver.class);
+			LocaleContext localeContext = localeContextResolver.resolveLocaleContext(exchange);
+			assertThat(localeContext.getLocale()).isEqualTo(StringUtils.parseLocaleString("nl_NL"));
+		});
+	}
+
+	@Test
+	void whenAcceptHeaderLocaleContextResolverIsUsedAndHeaderIsAbsentThenConfiguredLocaleIsUsed() {
+		this.contextRunner.withPropertyValues("spring.web.locale:en_UK").run((context) -> {
+			MockServerHttpRequest request = MockServerHttpRequest.get("/").build();
+			MockServerWebExchange exchange = MockServerWebExchange.from(request);
+			LocaleContextResolver localeContextResolver = context.getBean(LocaleContextResolver.class);
+			assertThat(localeContextResolver).isInstanceOf(AcceptHeaderLocaleContextResolver.class);
+			LocaleContext localeContext = localeContextResolver.resolveLocaleContext(exchange);
+			assertThat(localeContext.getLocale()).isEqualTo(StringUtils.parseLocaleString("en_UK"));
+		});
+	}
+
 	@Test
 	void customLocaleContextResolver() {
 		this.contextRunner.withUserConfiguration(LocaleContextResolverConfiguration.class)

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

@@ -38,6 +38,8 @@ import javax.servlet.http.HttpServletResponse;
 import javax.validation.ValidatorFactory;
 
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 
 import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration;
@@ -289,10 +291,11 @@ class WebMvcAutoConfigurationTests {
 		});
 	}
 
-	@Test
-	void overrideLocale() {
-		this.contextRunner.withPropertyValues("spring.mvc.locale:en_UK", "spring.mvc.locale-resolver=fixed")
-				.run((loader) -> {
+	@ParameterizedTest
+	@ValueSource(strings = { "mvc", "web" })
+	void overrideLocale(String mvcOrWeb) {
+		this.contextRunner.withPropertyValues("spring." + mvcOrWeb + ".locale:en_UK",
+				"spring." + mvcOrWeb + ".locale-resolver=fixed").run((loader) -> {
 					// mock request and set user preferred locale
 					MockHttpServletRequest request = new MockHttpServletRequest();
 					request.addPreferredLocale(StringUtils.parseLocaleString("nl_NL"));
@@ -306,9 +309,10 @@ class WebMvcAutoConfigurationTests {
 				});
 	}
 
-	@Test
-	void useAcceptHeaderLocale() {
-		this.contextRunner.withPropertyValues("spring.mvc.locale:en_UK").run((loader) -> {
+	@ParameterizedTest
+	@ValueSource(strings = { "mvc", "web" })
+	void useAcceptHeaderLocale(String mvcOrWeb) {
+		this.contextRunner.withPropertyValues("spring." + mvcOrWeb + ".locale:en_UK").run((loader) -> {
 			// mock request and set user preferred locale
 			MockHttpServletRequest request = new MockHttpServletRequest();
 			request.addPreferredLocale(StringUtils.parseLocaleString("nl_NL"));
@@ -321,9 +325,10 @@ class WebMvcAutoConfigurationTests {
 		});
 	}
 
-	@Test
-	void useDefaultLocaleIfAcceptHeaderNoSet() {
-		this.contextRunner.withPropertyValues("spring.mvc.locale:en_UK").run((context) -> {
+	@ParameterizedTest
+	@ValueSource(strings = { "mvc", "web" })
+	void useDefaultLocaleIfAcceptHeaderNoSet(String mvcOrWeb) {
+		this.contextRunner.withPropertyValues("spring." + mvcOrWeb + ".locale:en_UK").run((context) -> {
 			// mock request and set user preferred locale
 			MockHttpServletRequest request = new MockHttpServletRequest();
 			LocaleResolver localeResolver = context.getBean(LocaleResolver.class);