001/*
002 * Copyright 2002-2012 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.ui.context.support;
018
019import org.springframework.ui.context.HierarchicalThemeSource;
020import org.springframework.ui.context.Theme;
021import org.springframework.ui.context.ThemeSource;
022
023/**
024 * Empty ThemeSource that delegates all calls to the parent ThemeSource.
025 * If no parent is available, it simply won't resolve any theme.
026 *
027 * <p>Used as placeholder by UiApplicationContextUtils, if a context doesn't
028 * define its own ThemeSource. Not intended for direct use in applications.
029 *
030 * @author Juergen Hoeller
031 * @since 1.2.4
032 * @see UiApplicationContextUtils
033 */
034public class DelegatingThemeSource implements HierarchicalThemeSource {
035
036        private ThemeSource parentThemeSource;
037
038
039        @Override
040        public void setParentThemeSource(ThemeSource parentThemeSource) {
041                this.parentThemeSource = parentThemeSource;
042        }
043
044        @Override
045        public ThemeSource getParentThemeSource() {
046                return parentThemeSource;
047        }
048
049
050        @Override
051        public Theme getTheme(String themeName) {
052                if (this.parentThemeSource != null) {
053                        return this.parentThemeSource.getTheme(themeName);
054                }
055                else {
056                        return null;
057                }
058        }
059
060}