Handle blank Accept-Language header in AcceptHeaderLocaleResolver

elgun.shukurov · elgun.shukurov · commit c08f39e2a1fa · 2026-03-22T19:32:58.000+04:00
When the Accept-Language header is present but blank, defaultLocale was ignored and fell back to Locale.getDefault() (JVM system locale). A blank header represents the same intent as an absent header. Closes gh-36512
diff --git a/spring-webmvc/src/main/java/org/springframework/web/servlet/i18n/AcceptHeaderLocaleResolver.java b/spring-webmvc/src/main/java/org/springframework/web/servlet/i18n/AcceptHeaderLocaleResolver.java
@@ -85,7 +85,7 @@ public List<Locale> getSupportedLocales() {
 	@Override
 	public Locale resolveLocale(HttpServletRequest request) {
 		Locale defaultLocale = getDefaultLocale();
-		if (defaultLocale != null && request.getHeader("Accept-Language") == null) {
+		if (defaultLocale != null && !StringUtils.hasText(request.getHeader("Accept-Language"))) {
 			return defaultLocale;
 		}
 		Locale requestLocale = request.getLocale();
diff --git a/spring-webmvc/src/test/java/org/springframework/web/servlet/i18n/AcceptHeaderLocaleResolverTests.java b/spring-webmvc/src/test/java/org/springframework/web/servlet/i18n/AcceptHeaderLocaleResolverTests.java
@@ -105,6 +105,14 @@ void defaultLocale() {
 		assertThat(this.resolver.resolveLocale(request)).isEqualTo(US);
 	}
 
+	@Test
+	void defaultLocaleWithBlankAcceptLanguageHeader() {
+		this.resolver.setDefaultLocale(JAPANESE);
+		MockHttpServletRequest request = new MockHttpServletRequest();
+		request.addHeader("Accept-Language", "");
+		assertThat(this.resolver.resolveLocale(request)).isEqualTo(JAPANESE);
+	}
+
 
 	private HttpServletRequest request(Locale... locales) {
 		MockHttpServletRequest request = new MockHttpServletRequest();

Original file line number	Diff line number	Diff line change
`@@ -85,7 +85,7 @@ public List<Locale> getSupportedLocales() {`
`85`	`85`	`@Override`
`86`	`86`	`public Locale resolveLocale(HttpServletRequest request) {`
`87`	`87`	`Locale defaultLocale = getDefaultLocale();`
`88`		`- if (defaultLocale != null && request.getHeader("Accept-Language") == null) {`
	`88`	`+ if (defaultLocale != null && !StringUtils.hasText(request.getHeader("Accept-Language"))) {`
`89`	`89`	`return defaultLocale;`
`90`	`90`	`}`
`91`	`91`	`Locale requestLocale = request.getLocale();`