https://github.com/spring-projects/spring-framework: Spring Web MVC (Spring IO)
  • Juergen Hoeller 
/*
 * Copyright 2002-2017 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.web.servlet;

import java.util.Locale;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.lang.Nullable;


Interface for web-based locale resolution strategies that allows for
both locale resolution via the request and locale modification via
request and response.

This interface allows for implementations based on request, session, cookies, etc. The default implementation is AcceptHeaderLocaleResolver, simply using the request's locale provided by the respective HTTP header. 
Use RequestContext.getLocale() to retrieve the current locale in controllers or views, independent of the actual resolution strategy. 
Note: As of Spring 4.0, there is an extended strategy interface called LocaleContextResolver, allowing for resolution of a LocaleContext object, potentially including associated time zone information. Spring's provided resolver implementations implement the extended LocaleContextResolver interface wherever appropriate. 
Author:Juergen Hoeller
See Also:
Since:27.02.2003
/**
 * Interface for web-based locale resolution strategies that allows for
 * both locale resolution via the request and locale modification via
 * request and response.
 *
 * <p>This interface allows for implementations based on request, session,
 * cookies, etc. The default implementation is
 * {@link org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver},
 * simply using the request's locale provided by the respective HTTP header.
 *
 * <p>Use {@link org.springframework.web.servlet.support.RequestContext#getLocale()}
 * to retrieve the current locale in controllers or views, independent
 * of the actual resolution strategy.
 *
 * <p>Note: As of Spring 4.0, there is an extended strategy interface
 * called {@link LocaleContextResolver}, allowing for resolution of
 * a {@link org.springframework.context.i18n.LocaleContext} object,
 * potentially including associated time zone information. Spring's
 * provided resolver implementations implement the extended
 * {@link LocaleContextResolver} interface wherever appropriate.
 *
 * @author Juergen Hoeller
 * @since 27.02.2003
 * @see LocaleContextResolver
 * @see org.springframework.context.i18n.LocaleContextHolder
 * @see org.springframework.web.servlet.support.RequestContext#getLocale
 * @see org.springframework.web.servlet.support.RequestContextUtils#getLocale
 */
public interface LocaleResolver {

	
Resolve the current locale via the given request.
Can return a default locale as fallback in any case.

Params:
  • request – the request to resolve the locale for
Returns:the current locale (never null)
/**
	 * Resolve the current locale via the given request.
	 * Can return a default locale as fallback in any case.
	 * @param request the request to resolve the locale for
	 * @return the current locale (never {@code null})
	 */
	Locale resolveLocale(HttpServletRequest request);

	
Set the current locale to the given one.

Params:
  • request – the request to be used for locale modification
  • response – the response to be used for locale modification
  • locale – the new locale, or null to clear the locale
Throws:
/**
	 * Set the current locale to the given one.
	 * @param request the request to be used for locale modification
	 * @param response the response to be used for locale modification
	 * @param locale the new locale, or {@code null} to clear the locale
	 * @throws UnsupportedOperationException if the LocaleResolver
	 * implementation does not support dynamic changing of the locale
	 */
	void setLocale(HttpServletRequest request, @Nullable HttpServletResponse response, @Nullable Locale locale);

}