001/* 002 * Copyright 2002-2017 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.web.servlet; 018 019import java.util.Locale; 020 021import javax.servlet.http.HttpServletRequest; 022import javax.servlet.http.HttpServletResponse; 023 024import org.springframework.lang.Nullable; 025 026/** 027 * Interface for web-based locale resolution strategies that allows for 028 * both locale resolution via the request and locale modification via 029 * request and response. 030 * 031 * <p>This interface allows for implementations based on request, session, 032 * cookies, etc. The default implementation is 033 * {@link org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver}, 034 * simply using the request's locale provided by the respective HTTP header. 035 * 036 * <p>Use {@link org.springframework.web.servlet.support.RequestContext#getLocale()} 037 * to retrieve the current locale in controllers or views, independent 038 * of the actual resolution strategy. 039 * 040 * <p>Note: As of Spring 4.0, there is an extended strategy interface 041 * called {@link LocaleContextResolver}, allowing for resolution of 042 * a {@link org.springframework.context.i18n.LocaleContext} object, 043 * potentially including associated time zone information. Spring's 044 * provided resolver implementations implement the extended 045 * {@link LocaleContextResolver} interface wherever appropriate. 046 * 047 * @author Juergen Hoeller 048 * @since 27.02.2003 049 * @see LocaleContextResolver 050 * @see org.springframework.context.i18n.LocaleContextHolder 051 * @see org.springframework.web.servlet.support.RequestContext#getLocale 052 * @see org.springframework.web.servlet.support.RequestContextUtils#getLocale 053 */ 054public interface LocaleResolver { 055 056 /** 057 * Resolve the current locale via the given request. 058 * Can return a default locale as fallback in any case. 059 * @param request the request to resolve the locale for 060 * @return the current locale (never {@code null}) 061 */ 062 Locale resolveLocale(HttpServletRequest request); 063 064 /** 065 * Set the current locale to the given one. 066 * @param request the request to be used for locale modification 067 * @param response the response to be used for locale modification 068 * @param locale the new locale, or {@code null} to clear the locale 069 * @throws UnsupportedOperationException if the LocaleResolver 070 * implementation does not support dynamic changing of the locale 071 */ 072 void setLocale(HttpServletRequest request, @Nullable HttpServletResponse response, @Nullable Locale locale); 073 074}