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 javax.servlet.http.HttpServletRequest;
020import javax.servlet.http.HttpServletResponse;
021
022import org.springframework.lang.Nullable;
023
024/**
025 * Interface for web-based theme resolution strategies that allows for
026 * both theme resolution via the request and theme modification via
027 * request and response.
028 *
029 * <p>This interface allows for implementations based on session,
030 * cookies, etc. The default implementation is
031 * {@link org.springframework.web.servlet.theme.FixedThemeResolver},
032 * simply using a configured default theme.
033 *
034 * <p>Note that this resolver is only responsible for determining the
035 * current theme name. The Theme instance for the resolved theme name
036 * gets looked up by DispatcherServlet via the respective ThemeSource,
037 * i.e. the current WebApplicationContext.
038 *
039 * <p>Use {@link org.springframework.web.servlet.support.RequestContext#getTheme()}
040 * to retrieve the current theme in controllers or views, independent
041 * of the actual resolution strategy.
042 *
043 * @author Jean-Pierre Pawlak
044 * @author Juergen Hoeller
045 * @since 17.06.2003
046 * @see org.springframework.ui.context.Theme
047 * @see org.springframework.ui.context.ThemeSource
048 */
049public interface ThemeResolver {
050
051        /**
052         * Resolve the current theme name via the given request.
053         * Should return a default theme as fallback in any case.
054         * @param request the request to be used for resolution
055         * @return the current theme name
056         */
057        String resolveThemeName(HttpServletRequest request);
058
059        /**
060         * Set the current theme name to the given one.
061         * @param request the request to be used for theme name modification
062         * @param response the response to be used for theme name modification
063         * @param themeName the new theme name ({@code null} or empty to reset it)
064         * @throws UnsupportedOperationException if the ThemeResolver implementation
065         * does not support dynamic changing of the theme
066         */
067        void setThemeName(HttpServletRequest request, @Nullable HttpServletResponse response, @Nullable String themeName);
068
069}