001    // Copyright 2006, 2008, 2010, 2011 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    
015    package org.apache.tapestry5.services;
016    
017    import java.util.Map;
018    
019    import org.apache.tapestry5.internal.services.assets.ClasspathAssetRequestHandler;
020    import org.apache.tapestry5.ioc.annotations.UsesMappedConfiguration;
021    
022    /**
023     * Used as part of the support for classpath {@link org.apache.tapestry5.Asset}s, to convert the Asset's
024     * {@link org.apache.tapestry5.ioc.Resource} to a URL that can be accessed by the client. The asset path, within the
025     * classpath, is converted into a shorter virtual path. The term "alias" here is generally referred to as
026     * "virtual folder" elsewhere.
027     * <p/>
028     * Service configuration is a map from folder aliases (short names) to complete paths. Names should not start or end end
029     * with a slash. Generally, an alias should be a single name (not contain a slash). Paths should also not start or end
030     * with a slash. An example mapping would be <code>mylib</code> to <code>com/example/mylib</code>.
031     * <p>
032     * As originally envisioned, this service would simply <em>optimize</em> classpath assets, allowing the URL path for
033     * such assets to be shortened (and have a version number added, important for caching); thus the word "alias" makes
034     * sense ... it was responsible for creating an "alias" URL shorter than the default "classpath" URL.
035     * <p>
036     * Starting in Tapestry 5.2, this changed; all classpath assets <strong>must</strong> be "aliased" to a shorter URL
037     * path. Any URL that can not be shortened is now rejected. This simplifies creating new libraries, but also helps with
038     * security concerns, as it limits which portions of the classpath can <em>ever</em> be exposed to the user agent.
039     * <p>
040     * Tapestry automatically contributes a number of mappings: for the application root package itself (as alias "app") and
041     * for each library (via {@link ComponentClassResolver#getFolderToPackageMapping()});
042     */
043    @UsesMappedConfiguration(String.class)
044    public interface ClasspathAssetAliasManager
045    {
046        /**
047         * Takes a resource path to a classpath resource and adds the asset path prefix to the path. May also convert part
048         * of the path to an alias (based on the manager's configuration).
049         * 
050         * @param resourcePath
051         *            resource path on the classpath (with no leading slash)
052         * @return URL ready to send to the client
053         */
054        String toClientURL(String resourcePath);
055    
056        /**
057         * Returns the mappings used by the service: the keys are the folder aliases (i.e, "corelib")
058         * and the values are the corresponding paths (i.e., "org/apache/tapestry5/corelib"). This
059         * exists primarily so that {@link ClasspathAssetRequestHandler}s can be created automatically
060         * for each mapping.
061         * 
062         * @since 5.2.0
063         **/
064        Map<String, String> getMappings();
065    }