// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package org.apache.tapestry5;
import org.apache.tapestry5.ioc.Resource;
/**
* An Asset is any kind of resource that can be exposed to the client web browser. Although quite often an Asset is a
* resource in a web application's context folder, within Tapestry, Assets may also be resources on the classpath (i.e.,
* packaged inside JARs).
*
* An Asset's toString() will return the URL for the resource (the same value as {@link #toClientURL()}).
*
* Release 5.1.0.0 introduced {@link org.apache.tapestry5.Asset2}, which extends this interface with an additional
* method.
*
* @see org.apache.tapestry5.services.AssetPathConverter
*/
public interface Asset
{
/**
* Returns a URL that can be passed, unchanged, to the client in order for it to access the resource. The same value
* is returned from <code>toString()</code>.
*
* Tapestry's built-in asset types (context and classpath) always incorporate a checksum as part of the path,
* and alternate implementations are encouraged to do so as well. In addition, Tapestry ensures that context and
* classpath assets have a far-future expires header (to ensure aggressive caching by the client).
* Note that starting in Tapestry 5.4, it is expected that Asset instances recognize
* when the underlying Resource's content has changed, and update the clientURL to reflect the new content's
* checksum. This wasn't an issue in earlier releases where the clientURL incorporated a version number.
*
* Finally, starting in 5.4, this value will often be <em>variant</em>: the exact URL returned will depend on
* whether the underlying resource content is compressable, whether the current {@link org.apache.tapestry5.services.Request}
* supports compression.
*
* @see org.apache.tapestry5.services.AssetSource
* @see org.apache.tapestry5.services.AssetPathConverter
*/
String toClientURL();
/**
* Returns the underlying Resource for the Asset.
*/
Resource getResource();
}