001// Copyright 2006, 2007, 2008, 2009, 2010 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007// http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry5.services;
016
017import org.apache.tapestry5.Asset;
018import org.apache.tapestry5.ioc.Resource;
019import org.apache.tapestry5.ioc.annotations.UsesMappedConfiguration;
020import org.apache.tapestry5.ioc.services.SymbolSource;
021import org.apache.tapestry5.ioc.services.ThreadLocale;
022
023import java.util.Locale;
024
025/**
026 * Used to find or create an {@link org.apache.tapestry5.Asset} with a given path.
027 * <p/>
028 * Assets are defined with a domain, and the domain is indicated by a prefix. The two builtin domains are "context:"
029 * (for files inside the web application context) and "classpath:" for files stored on the classpath (typically, inside
030 * a JAR, such as a component library). Other domains can be defined via contributions to the AssetSource service.
031 * <p/>
032 * Since 5.1.0.0, is is preferred that
033 * {@link org.apache.tapestry5.services.AssetFactory#createAsset(org.apache.tapestry5.ioc.Resource)} return an instance
034 * of {@link org.apache.tapestry5.Asset2}.
035 */
036@UsesMappedConfiguration(AssetFactory.class)
037public interface AssetSource
038{
039    /**
040     * Finds the asset. The path may either be a simple file name or a relative path (relative to the base resource)
041     * <em>or</em> it may have a prefix, such as "context:" or "classpath:", in which case it is treated as a complete
042     * path within the indicated domain. The resulting Resource is then localized (to the provided Locale) and returned
043     * as an Asset.
044     * <p/>
045     * The AssetSource caches its results, so a single Asset instance may be shared among many different components.
046     * 
047     * @param baseResource
048     *            base resource for computing relative paths, or null to search the classpath
049     * @param path
050     *            relative to the base resource
051     * @param locale
052     *            locale to localize the final resource to, or null for the thread's current locale
053     * @return the asset
054     * @throws RuntimeException
055     *             if the asset can not be found
056     */
057    Asset getAsset(Resource baseResource, String path, Locale locale);
058
059    /**
060     * Finds the asset, either on the classpath or (if prefixed), within the indicated domain. The result is not
061     * localized. The underlying Asset may not exist.
062     * 
063     * @param path
064     *            to the resource to provide as an Asset
065     * @return Resource for the path (the Resource may not exist)
066     * @since 5.1.0.0
067     */
068    Resource resourceForPath(String path);
069
070    /**
071     * Convienience for finding assets on the classpath.
072     * 
073     * @param path
074     *            path to the base resource, relative to classpath root
075     * @param locale
076     *            to localize the resource to
077     * @return the asset
078     * @throws RuntimeException
079     *             if the asset can not be found
080     */
081    Asset getClasspathAsset(String path, Locale locale);
082
083    /**
084     * Convienience for finding assets in the context.
085     * 
086     * @param path
087     *            path relative to the base resource (the context root)
088     * @param locale
089     *            to localize the resource to, or null for the locale for the current request
090     * @return the asset
091     * @throws RuntimeException
092     *             if the asset can not be found
093     * @since 5.1.0.0
094     */
095    Asset getContextAsset(String path, Locale locale);
096
097    /**
098     * Obtains a classpath alias in the current locale (as defined by the {@link ThreadLocale} service).
099     * 
100     * @param path
101     *            relative to the classpath root
102     * @return the asset
103     * @throws RuntimeException
104     *             if the asset can not be found
105     */
106    Asset getClasspathAsset(String path);
107
108    /**
109     * Find an asset but does not attempt to localize it. If the path has no prefix, it is assumed to
110     * be on the classpath.
111     * 
112     * @since 5.2.0
113     * @throws RuntimeException
114     *             if the asset can not be found
115     */
116    Asset getUnlocalizedAsset(String path);
117
118    /**
119     * As with {@link #getUnlocalizedAsset(String)}, but {@linkplain SymbolSource#expandSymbols(String) symbols
120     * in the path are expanded}.
121     * 
122     * @since 5.2.0
123     */
124    Asset getExpandedAsset(String path);
125}