Simplify default locale/timezone resolution in cookie/session locale resolvers

spring-webmvc/src/main/java/org/springframework/web/servlet/LocaleContextResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -22,12 +22,16 @@
 import jakarta.servlet.http.HttpServletResponse;
 
 import org.springframework.context.i18n.LocaleContext;
+import org.springframework.context.i18n.SimpleLocaleContext;
 import org.springframework.lang.Nullable;
 
 /**
  * Extension of {@link LocaleResolver}, adding support for a rich locale context
  * (potentially including locale and time zone information).
  *
+ * <p>Also provides pre-implemented versions of {@link #resolveLocale} and {@link #setLocale},
+ * delegating to {@link #resolveLocaleContext} and {@link #setLocaleContext}.
+ *
  * @author Juergen Hoeller
  * @since 4.0
  * @see org.springframework.context.i18n.LocaleContext
@@ -73,4 +77,15 @@ public interface LocaleContextResolver extends LocaleResolver {
 	void setLocaleContext(HttpServletRequest request, @Nullable HttpServletResponse response,
 			@Nullable LocaleContext localeContext);
 
+	@Override
+	default Locale resolveLocale(HttpServletRequest request) {
+		Locale locale = resolveLocaleContext(request).getLocale();
+		return (locale != null ? locale : request.getLocale());
+	}
+
+	@Override
+	default void setLocale(HttpServletRequest request, @Nullable HttpServletResponse response, @Nullable Locale locale) {
+		setLocaleContext(request, response, (locale != null ? new SimpleLocaleContext(locale) : null));
+	}
+
 }

spring-webmvc/src/main/java/org/springframework/web/servlet/i18n/AbstractLocaleContextResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -16,23 +16,15 @@
 
 package org.springframework.web.servlet.i18n;
 
-import java.util.Locale;
 import java.util.TimeZone;
 
-import jakarta.servlet.http.HttpServletRequest;
-import jakarta.servlet.http.HttpServletResponse;
-
-import org.springframework.context.i18n.SimpleLocaleContext;
 import org.springframework.lang.Nullable;
 import org.springframework.web.servlet.LocaleContextResolver;
 
 /**
  * Abstract base class for {@link LocaleContextResolver} implementations.
  * Provides support for a default locale and a default time zone.
  *
- * <p>Also provides pre-implemented versions of {@link #resolveLocale} and {@link #setLocale},
- * delegating to {@link #resolveLocaleContext} and {@link #setLocaleContext}.
- *
  * @author Juergen Hoeller
  * @since 4.0
  * @see #setDefaultLocale
@@ -59,16 +51,4 @@ public TimeZone getDefaultTimeZone() {
 		return this.defaultTimeZone;
 	}
 
-
-	@Override
-	public Locale resolveLocale(HttpServletRequest request) {
-		Locale locale = resolveLocaleContext(request).getLocale();
-		return (locale != null ? locale : request.getLocale());
-	}
-
-	@Override
-	public void setLocale(HttpServletRequest request, @Nullable HttpServletResponse response, @Nullable Locale locale) {
-		setLocaleContext(request, response, (locale != null ? new SimpleLocaleContext(locale) : null));
-	}
-
 }

spring-webmvc/src/main/java/org/springframework/web/servlet/i18n/AcceptHeaderLocaleResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -33,21 +33,18 @@
  * specified in the "accept-language" header of the HTTP request (that is,
  * the locale sent by the client browser, normally that of the client's OS).
  *
- * <p>Note: Does not support {@code setLocale}, since the accept header
+ * <p>Note: Does not support {@code setLocale}, since the "accept-header"
  * can only be changed through changing the client's locale settings.
  *
  * @author Juergen Hoeller
  * @author Rossen Stoyanchev
  * @since 27.02.2003
  * @see jakarta.servlet.http.HttpServletRequest#getLocale()
  */
-public class AcceptHeaderLocaleResolver implements LocaleResolver {
+public class AcceptHeaderLocaleResolver extends AbstractLocaleResolver {
 
 	private final List<Locale> supportedLocales = new ArrayList<>(4);
 
-	@Nullable
-	private Locale defaultLocale;
-
 
 	/**
 	 * Configure supported locales to check against the requested locales
@@ -69,29 +66,6 @@ public List<Locale> getSupportedLocales() {
 		return this.supportedLocales;
 	}
 
-	/**
-	 * Configure a fixed default locale to fall back on if the request does not
-	 * have an "Accept-Language" header.
-	 * <p>By default this is not set in which case when there is no "Accept-Language"
-	 * header, the default locale for the server is used as defined in
-	 * {@link HttpServletRequest#getLocale()}.
-	 * @param defaultLocale the default locale to use
-	 * @since 4.3
-	 */
-	public void setDefaultLocale(@Nullable Locale defaultLocale) {
-		this.defaultLocale = defaultLocale;
-	}
-
-	/**
-	 * The configured default locale, if any.
-	 * <p>This method may be overridden in subclasses.
-	 * @since 4.3
-	 */
-	@Nullable
-	public Locale getDefaultLocale() {
-		return this.defaultLocale;
-	}
-
 
 	@Override
 	public Locale resolveLocale(HttpServletRequest request) {

spring-webmvc/src/main/java/org/springframework/web/servlet/i18n/CookieLocaleResolver.java

@@ -18,6 +18,7 @@
 
 import java.util.Locale;
 import java.util.TimeZone;
+import java.util.function.Function;
 
 import jakarta.servlet.http.Cookie;
 import jakarta.servlet.http.HttpServletRequest;
@@ -50,6 +51,7 @@
  *
  * @author Juergen Hoeller
  * @author Jean-Pierre Pawlak
+ * @author Vedran Pavic
  * @since 27.02.2003
  * @see #setDefaultLocale
  * @see #setDefaultTimeZone
@@ -94,6 +96,15 @@ public class CookieLocaleResolver extends CookieGenerator implements LocaleConte
 	@Nullable
 	private TimeZone defaultTimeZone;
 
+	private Function<HttpServletRequest, Locale> defaultLocaleFunction = request -> {
+		Locale defaultLocale = getDefaultLocale();
+		if (defaultLocale == null) {
+			defaultLocale = request.getLocale();
+		}
+		return defaultLocale;
+	};
+
+	private Function<HttpServletRequest, TimeZone> defaultTimeZoneFunction = request -> getDefaultTimeZone();
 
 	/**
 	 * Create a new instance of the {@link CookieLocaleResolver} class
@@ -137,8 +148,8 @@ public boolean isLanguageTagCompliant() {
 	 * @since 5.1.7
 	 * @see #setDefaultLocale
 	 * @see #setDefaultTimeZone
-	 * @see #determineDefaultLocale
-	 * @see #determineDefaultTimeZone
+	 * @see #setDefaultLocaleFunction(Function)
+	 * @see #setDefaultTimeZoneFunction(Function)
 	 */
 	public void setRejectInvalidCookies(boolean rejectInvalidCookies) {
 		this.rejectInvalidCookies = rejectInvalidCookies;
@@ -186,6 +197,35 @@ protected TimeZone getDefaultTimeZone() {
 		return this.defaultTimeZone;
 	}
 
+	/**
+	 * Set the function used to determine the default locale for the given request,
+	 * called if no {@link Locale} session attribute has been found.
+	 * <p>The default implementation returns the specified default locale,
+	 * if any, else falls back to the request's accept-header locale.
+	 * @param defaultLocaleFunction the function used to determine the default locale
+	 * @since 6.0
+	 * @see #setDefaultLocale
+	 * @see jakarta.servlet.http.HttpServletRequest#getLocale()
+	 */
+	public void setDefaultLocaleFunction(Function<HttpServletRequest, Locale> defaultLocaleFunction) {
+		Assert.notNull(defaultLocaleFunction, "defaultLocaleFunction must not be null");
+		this.defaultLocaleFunction = defaultLocaleFunction;
+	}
+
+	/**
+	 * Set the function used to determine the default time zone for the given request,
+	 * called if no {@link TimeZone} session attribute has been found.
+	 * <p>The default implementation returns the specified default time zone,
+	 * if any, or {@code null} otherwise.
+	 * @param defaultTimeZoneFunction the function used to determine the default time zone
+	 * @since 6.0
+	 * @see #setDefaultTimeZone
+	 */
+	public void setDefaultTimeZoneFunction(Function<HttpServletRequest, TimeZone> defaultTimeZoneFunction) {
+		Assert.notNull(defaultTimeZoneFunction, "defaultTimeZoneFunction must not be null");
+		this.defaultTimeZoneFunction = defaultTimeZoneFunction;
+	}
+
 
 	@Override
 	public Locale resolveLocale(HttpServletRequest request) {
@@ -260,9 +300,9 @@ private void parseLocaleCookieIfNecessary(HttpServletRequest request) {
 			}
 
 			request.setAttribute(LOCALE_REQUEST_ATTRIBUTE_NAME,
-					(locale != null ? locale : determineDefaultLocale(request)));
+					(locale != null ? locale : this.defaultLocaleFunction.apply(request)));
 			request.setAttribute(TIME_ZONE_REQUEST_ATTRIBUTE_NAME,
-					(timeZone != null ? timeZone : determineDefaultTimeZone(request)));
+					(timeZone != null ? timeZone : this.defaultTimeZoneFunction.apply(request)));
 		}
 	}
 
@@ -291,9 +331,9 @@ public void setLocaleContext(HttpServletRequest request, @Nullable HttpServletRe
 			removeCookie(response);
 		}
 		request.setAttribute(LOCALE_REQUEST_ATTRIBUTE_NAME,
-				(locale != null ? locale : determineDefaultLocale(request)));
+				(locale != null ? locale : this.defaultLocaleFunction.apply(request)));
 		request.setAttribute(TIME_ZONE_REQUEST_ATTRIBUTE_NAME,
-				(timeZone != null ? timeZone : determineDefaultTimeZone(request)));
+				(timeZone != null ? timeZone : this.defaultTimeZoneFunction.apply(request)));
 	}
 
 
@@ -334,13 +374,11 @@ protected String toLocaleValue(Locale locale) {
 	 * @return the default locale (never {@code null})
 	 * @see #setDefaultLocale
 	 * @see jakarta.servlet.http.HttpServletRequest#getLocale()
+	 * @deprecated as of 6.0, in favor of {@link #setDefaultLocaleFunction(Function)}
 	 */
+	@Deprecated
 	protected Locale determineDefaultLocale(HttpServletRequest request) {
-		Locale defaultLocale = getDefaultLocale();
-		if (defaultLocale == null) {
-			defaultLocale = request.getLocale();
-		}
-		return defaultLocale;
+		return this.defaultLocaleFunction.apply(request);
 	}
 
 	/**
@@ -351,10 +389,12 @@ protected Locale determineDefaultLocale(HttpServletRequest request) {
 	 * @param request the request to resolve the time zone for
 	 * @return the default time zone (or {@code null} if none defined)
 	 * @see #setDefaultTimeZone
+	 * @deprecated as of 6.0, in favor of {@link #setDefaultTimeZoneFunction(Function)}
 	 */
+	@Deprecated
 	@Nullable
 	protected TimeZone determineDefaultTimeZone(HttpServletRequest request) {
-		return getDefaultTimeZone();
+		return this.defaultTimeZoneFunction.apply(request);
 	}
 
 }