001    // Copyright 2006, 2008, 2009 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;
016    
017    import org.apache.tapestry5.ioc.Resource;
018    
019    /**
020     * An Asset is any kind of resource that can be exposed to the client web browser. Although quite often an Asset is a
021     * resource in a web application's context folder, within Tapestry, Assets may also be resources on the classpath (i.e.,
022     * packaged inside JARs).
023     * <p/>
024     * An Asset's toString() will return the URL for the resource (the same value as {@link #toClientURL()}).
025     * <p/>
026     * Release 5.1.0.0 introduced {@link org.apache.tapestry5.Asset2}, which extends this interface with an additional
027     * method.
028     *
029     * @see org.apache.tapestry5.services.AssetPathConverter
030     */
031    public interface Asset
032    {
033        /**
034         * Returns a URL that can be passed, unchanged, to the client in order for it to access the resource. The same value
035         * is returned from <code>toString()</code>.
036         * <p/>
037         * Tapestry's built-in asset types (context and classpath) always incorporate a version number as part of the path,
038         * and alternate implementations are encouraged to do so as well. In addition, Tapestry ensures that context and
039         * classpath assets have a far-future expires header (to ensure aggressive caching by the client).
040         * <p/>
041         */
042        String toClientURL();
043    
044        /**
045         * Returns the underlying Resource for the Asset.
046         */
047        Resource getResource();
048    
049    }