001// Copyright 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 015package org.apache.tapestry5; 016 017/** 018 * Extension to {@link org.apache.tapestry5.Asset} that adds a method to determine if the asset is invariant or not. 019 * {@link org.apache.tapestry5.services.AssetFactory} instances should ideally return Asset2 objects, not Asset. This is 020 * only of primary interest to the {@link org.apache.tapestry5.internal.bindings.AssetBindingFactory}, as it determines 021 * the invariance of the binding from the asset (and assumes variant unless the asset object implements this 022 * interface). 023 * 024 * @since 5.1.0.0 025 */ 026public interface Asset2 extends Asset 027{ 028 /** 029 * Returns true if the Asset is invariant (meaning that it returns the same value from {@link Asset#toClientURL()} 030 * at all times). Most Assets are invariant. Assets that are used as binding values will be cached more aggressively by Tapestry if they are 031 * invariant. 032 * 033 * @return true if invariant 034 * @see org.apache.tapestry5.services.AssetPathConverter#isInvariant() 035 * @see Binding#isInvariant() 036 */ 037 boolean isInvariant(); 038}