001/*
002 * Copyright 2002-2016 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;
020import javax.servlet.http.HttpServletRequest;
021import javax.servlet.http.HttpServletResponse;
022
023/**
024 * Interface for web-based locale resolution strategies that allows for
025 * both locale resolution via the request and locale modification via
026 * request and response.
027 *
028 * <p>This interface allows for implementations based on request, session,
029 * cookies, etc. The default implementation is
030 * {@link org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver},
031 * simply using the request's locale provided by the respective HTTP header.
032 *
033 * <p>Use {@link org.springframework.web.servlet.support.RequestContext#getLocale()}
034 * to retrieve the current locale in controllers or views, independent
035 * of the actual resolution strategy.
036 *
037 * <p>Note: As of Spring 4.0, there is an extended strategy interface
038 * called {@link LocaleContextResolver}, allowing for resolution of
039 * a {@link org.springframework.context.i18n.LocaleContext} object,
040 * potentially including associated time zone information. Spring's
041 * provided resolver implementations implement the extended
042 * {@link LocaleContextResolver} interface wherever appropriate.
043 *
044 * @author Juergen Hoeller
045 * @since 27.02.2003
046 * @see LocaleContextResolver
047 * @see org.springframework.context.i18n.LocaleContextHolder
048 * @see org.springframework.web.servlet.support.RequestContext#getLocale
049 * @see org.springframework.web.servlet.support.RequestContextUtils#getLocale
050 */
051public interface LocaleResolver {
052
053        /**
054         * Resolve the current locale via the given request.
055         * Can return a default locale as fallback in any case.
056         * @param request the request to resolve the locale for
057         * @return the current locale (never {@code null})
058         */
059        Locale resolveLocale(HttpServletRequest request);
060
061        /**
062         * Set the current locale to the given one.
063         * @param request the request to be used for locale modification
064         * @param response the response to be used for locale modification
065         * @param locale the new locale, or {@code null} to clear the locale
066         * @throws UnsupportedOperationException if the LocaleResolver
067         * implementation does not support dynamic changing of the locale
068         */
069        void setLocale(HttpServletRequest request, HttpServletResponse response, Locale locale);
070
071}