Add fixedlocaleresolver based on application property

If the user sets spring.mvc.locale and doesn't provide a @Bean
of type LocaleResolver then a FixedLocaleResolver will be provided.

Fixes gh-697, fixes gh-669

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

@@ -34,6 +34,7 @@ import org.springframework.boot.autoconfigure.AutoConfigureAfter;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnExpression;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
 import org.springframework.context.annotation.Bean;
@@ -49,10 +50,12 @@ import org.springframework.core.io.ResourceLoader;
 import org.springframework.format.Formatter;
 import org.springframework.format.FormatterRegistry;
 import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.util.StringUtils;
 import org.springframework.web.accept.ContentNegotiationManager;
 import org.springframework.web.context.request.RequestContextListener;
 import org.springframework.web.filter.HiddenHttpMethodFilter;
 import org.springframework.web.servlet.DispatcherServlet;
+import org.springframework.web.servlet.LocaleResolver;
 import org.springframework.web.servlet.View;
 import org.springframework.web.servlet.ViewResolver;
 import org.springframework.web.servlet.config.annotation.EnableWebMvc;
@@ -61,6 +64,7 @@ import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
 import org.springframework.web.servlet.handler.SimpleUrlHandlerMapping;
+import org.springframework.web.servlet.i18n.FixedLocaleResolver;
 import org.springframework.web.servlet.resource.ResourceHttpRequestHandler;
 import org.springframework.web.servlet.view.BeanNameViewResolver;
 import org.springframework.web.servlet.view.ContentNegotiatingViewResolver;
@@ -140,6 +144,9 @@ public class WebMvcAutoConfiguration {
 		@Value("${spring.resources.cachePeriod:}")
 		private Integer cachePeriod;
 		
+		@Value("${spring.mvc.locale:}")
+		private String locale = "";
+
 		@Autowired
 		private ListableBeanFactory beanFactory;
 
@@ -190,6 +197,13 @@ public class WebMvcAutoConfiguration {
 			return resolver;
 		}
 
+		@Bean
+		@ConditionalOnMissingBean(LocaleResolver.class)
+		@ConditionalOnExpression("'${spring.mvc.locale:}' != ''")
+		public LocaleResolver localeResolver() {
+			return new FixedLocaleResolver(StringUtils.parseLocaleString(this.locale));
+		}
+
 		@Override
 		public void addFormatters(FormatterRegistry registry) {
 			for (Converter<?, ?> converter : getBeansOfType(Converter.class)) {

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

@@ -19,6 +19,7 @@ package org.springframework.boot.autoconfigure.web;
 import java.lang.reflect.Field;
 import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 
 import javax.servlet.http.HttpServletRequest;
@@ -28,27 +29,34 @@ import org.junit.After;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
+import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.boot.autoconfigure.PropertyPlaceholderAutoConfiguration;
 import org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext;
 import org.springframework.boot.context.embedded.EmbeddedServletContainerCustomizerBeanPostProcessor;
 import org.springframework.boot.context.embedded.EmbeddedServletContainerFactory;
 import org.springframework.boot.context.embedded.MockEmbeddedServletContainerFactory;
+import org.springframework.boot.test.EnvironmentTestUtils;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.Resource;
+import org.springframework.mock.web.MockHttpServletRequest;
 import org.springframework.util.ReflectionUtils;
+import org.springframework.util.StringUtils;
 import org.springframework.web.servlet.HandlerAdapter;
 import org.springframework.web.servlet.HandlerMapping;
+import org.springframework.web.servlet.LocaleResolver;
 import org.springframework.web.servlet.View;
 import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
 import org.springframework.web.servlet.handler.SimpleUrlHandlerMapping;
+import org.springframework.web.servlet.i18n.FixedLocaleResolver;
 import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter;
 import org.springframework.web.servlet.resource.ResourceHttpRequestHandler;
 import org.springframework.web.servlet.view.AbstractView;
 
 import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.instanceOf;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertThat;
@@ -141,6 +149,40 @@ public class WebMvcAutoConfigurationTests {
 				equalTo((Resource) new ClassPathResource("/foo/")));
 	}
 
+	@Test(expected = NoSuchBeanDefinitionException.class)
+	public void noLocaleResolver() throws Exception {
+		this.context = new AnnotationConfigEmbeddedWebApplicationContext();
+		this.context.register(AllResources.class, Config.class,
+				WebMvcAutoConfiguration.class,
+				HttpMessageConvertersAutoConfiguration.class,
+				PropertyPlaceholderAutoConfiguration.class);
+		this.context.refresh();
+		this.context.getBean(LocaleResolver.class);
+	}
+
+	@Test
+	public void overrideLocale() throws Exception {
+		this.context = new AnnotationConfigEmbeddedWebApplicationContext();
+		// set fixed locale
+		EnvironmentTestUtils.addEnvironment(this.context,
+				"spring.mvc.locale:en_UK");
+		this.context.register(AllResources.class, Config.class,
+				WebMvcAutoConfiguration.class,
+				HttpMessageConvertersAutoConfiguration.class,
+				PropertyPlaceholderAutoConfiguration.class);
+		this.context.refresh();
+		// mock request and set user preferred locale
+		MockHttpServletRequest request = new MockHttpServletRequest();
+		request.addPreferredLocale(StringUtils.parseLocaleString("nl_NL"));
+		LocaleResolver localeResolver = this.context.getBean(LocaleResolver.class);
+		Locale locale = localeResolver.resolveLocale(request);
+		assertThat(localeResolver,
+				instanceOf(FixedLocaleResolver.class));
+		// test locale resolver uses fixed locale and not user preferred locale
+		assertThat(locale.toString(),
+				equalTo("en_UK"));
+	}
+
 	@SuppressWarnings("unchecked")
 	protected Map<String, List<Resource>> getMappingLocations()
 			throws IllegalAccessException {

spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -67,6 +67,7 @@ content into your application; rather pick only the properties that you need.
 	# SPRING MVC ({sc-spring-boot-autoconfigure}/web/HttpMapperProperties.{sc-ext}[HttpMapperProperties])
 	http.mappers.json-pretty-print=false # pretty print JSON
 	http.mappers.json-sort-keys=false # sort keys
+	spring.mvc.locale= # set fixed locale, e.g. en_UK
 	spring.view.prefix= # MVC view prefix
 	spring.view.suffix= # ... and suffix
 	spring.resources.cache-period= # cache timeouts in headers sent to browser