    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    }