001/*
002 * Copyright 2002-2013 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.theme;
018
019import javax.servlet.ServletException;
020import javax.servlet.http.HttpServletRequest;
021import javax.servlet.http.HttpServletResponse;
022
023import org.springframework.web.servlet.ThemeResolver;
024import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;
025import org.springframework.web.servlet.support.RequestContextUtils;
026
027/**
028 * Interceptor that allows for changing the current theme on every request,
029 * via a configurable request parameter (default parameter name: "theme").
030 *
031 * @author Juergen Hoeller
032 * @since 20.06.2003
033 * @see org.springframework.web.servlet.ThemeResolver
034 */
035public class ThemeChangeInterceptor extends HandlerInterceptorAdapter {
036
037        /**
038         * Default name of the theme specification parameter: "theme".
039         */
040        public static final String DEFAULT_PARAM_NAME = "theme";
041
042        private String paramName = DEFAULT_PARAM_NAME;
043
044
045        /**
046         * Set the name of the parameter that contains a theme specification
047         * in a theme change request. Default is "theme".
048         */
049        public void setParamName(String paramName) {
050                this.paramName = paramName;
051        }
052
053        /**
054         * Return the name of the parameter that contains a theme specification
055         * in a theme change request.
056         */
057        public String getParamName() {
058                return this.paramName;
059        }
060
061
062        @Override
063        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
064                        throws ServletException {
065
066                String newTheme = request.getParameter(this.paramName);
067                if (newTheme != null) {
068                        ThemeResolver themeResolver = RequestContextUtils.getThemeResolver(request);
069                        if (themeResolver == null) {
070                                throw new IllegalStateException("No ThemeResolver found: not in a DispatcherServlet request?");
071                        }
072                        themeResolver.setThemeName(request, response, newTheme);
073                }
074                // Proceed in any case.
075                return true;
076        }
077
078}