// Copyright 2009 The Apache Software Foundation

 //

 // 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;

 /**

  * Extension to {@link org.apache.tapestry5.Asset} that adds a method to determine if the asset is invariant or not.

  * {@link org.apache.tapestry5.services.AssetFactory} instances should ideally return Asset2 objects, not Asset. This is

  * only of primary interest to the {@link org.apache.tapestry5.internal.bindings.AssetBindingFactory}, as it determines

  * the invariance of the binding from the asset (and assumes variant unless the asset object implements this

  * interface).

  *

  * @since 5.1.0.0

  */

 public interface Asset2 extends Asset

 {

     /**

      * Returns true if the Asset is invariant (meaning that it returns the same value from {@link Asset#toClientURL()}

      * at all times}. Assets that are used as binding values will be cached more aggresively by Tapestry as they are

      * invariant.

      *

      * @return true if invariant

      * @see org.apache.tapestry5.services.AssetPathConverter#isInvariant()

      * @see Binding#isInvariant()

      */

     boolean isInvariant();

 }