001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.wicket.markup.resolver;
018
019import org.apache.wicket.Application;
020import org.apache.wicket.Component;
021import org.apache.wicket.MarkupContainer;
022import org.apache.wicket.markup.ComponentTag;
023import org.apache.wicket.markup.MarkupStream;
024
025/**
026 * Utility class for {@link IComponentResolver}s
027 * 
028 * @author igor.vaynberg
029 */
030public class ComponentResolvers
031{
032        private ComponentResolvers()
033        {
034        }
035
036        /**
037         * Attempts to resolve a component using resolvers. Tries resolvers in the component hierarchy
038         * as well as application-wide.
039         * <p>
040         * This method encapsulates the contract of resolving components and should be used any time a
041         * component needs to be resolved under normal circumstances.
042         * </p>
043         * 
044         * @param container
045         *            The container parsing its markup
046         * @param markupStream
047         *            The current markupStream
048         * @param tag
049         *            The current component tag while parsing the markup
050         * @param filter
051         *            A filter for application-wide resolvers
052         * @return component or {@code null} if not found
053         */
054        public static Component resolve(final MarkupContainer container,
055                final MarkupStream markupStream, final ComponentTag tag, final ResolverFilter filter)
056        {
057                // try to resolve using component hierarchy
058                Component component = resolveByComponentHierarchy(container, markupStream, tag);
059
060                if (component == null)
061                {
062                        // fallback to application-level resolvers
063                        component = resolveByApplication(container, markupStream, tag, filter);
064                }
065
066                return component;
067        }
068
069        /**
070         * Attempts to resolve a component via application registered resolvers.
071         * 
072         * @param container
073         * @param markupStream
074         * @param tag
075         * @param filter
076         * @return Null, if no component was found
077         */
078        public static Component resolveByApplication(final MarkupContainer container,
079                final MarkupStream markupStream, final ComponentTag tag, final ResolverFilter filter)
080        {
081                for (final IComponentResolver resolver : Application.get()
082                        .getPageSettings()
083                        .getComponentResolvers())
084                {
085                        if ((filter == null) || (filter.ignoreResolver(resolver) == false))
086                        {
087                                Component component = resolver.resolve(container, markupStream, tag);
088                                if (component != null)
089                                {
090                                        return component;
091                                }
092                        }
093                }
094
095                return null;
096        }
097
098        /**
099         * Attempts to resolve a component via the component hierarchy using resolvers.
100         * 
101         * @param container
102         * @param markupStream
103         * @param tag
104         * @return Null, if no component was found
105         */
106        public static Component resolveByComponentHierarchy(final MarkupContainer container,
107                final MarkupStream markupStream, final ComponentTag tag)
108        {
109                Component cursor = container;
110                while (cursor != null)
111                {
112                        if (cursor instanceof IComponentResolver)
113                        {
114                                IComponentResolver resolver = (IComponentResolver)cursor;
115                                Component component = resolver.resolve(container, markupStream, tag);
116                                if (component != null)
117                                {
118                                        return component;
119                                }
120                        }
121                        cursor = cursor.getParent();
122                }
123
124                return null;
125        }
126
127        public interface ResolverFilter
128        {
129                /**
130                 * 
131                 * @param resolver
132                 * @return true, if resolvers should be skipped
133                 */
134                boolean ignoreResolver(IComponentResolver resolver);
135        }
136}