001// Copyright 2009, 2013 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.services; 016 017/** 018 * Converts the {@linkplain org.apache.tapestry5.Asset#toClientURL() path (or URI) of an asset} into a new format. This 019 * is the <em>hook</em> needed to make use of a <a href="http://en.wikipedia.org/wiki/Content_Delivery_Network">Content 020 * Delivery Network</a>. 021 * <p/> 022 * The default implementation of this is <em>identity</em>, the URI is passed through unchanged. Using a contribution to 023 * the {@link org.apache.tapestry5.ioc.services.ServiceOverride} service, you may override the default implementation. 024 * 025 * @since 5.1.0.0 026 */ 027public interface AssetPathConverter 028{ 029 /** 030 * Returns true if the converter returns the exact same converted path for any specific asset path (in which case, the 031 * converted asset path may be cached in component instance variables more aggressively). This value should be false 032 * if the converted path can vary for the same input path ... that is, if external factors (such as the identity of 033 * the user, or information obtained from the request) is involved in generating the final client URI. With a CDN 034 * this can sometimes be the case, where the user's identity may indicate which CDN server to vend the asset from. 035 * 036 * @return true if invariant (and therefore cacheable) 037 */ 038 boolean isInvariant(); 039 040 /** 041 * Converts the default asset client URI to its final form, ready to be sent to the client. The default asset path 042 * is an absolute path (it starts with a leading slash) and incorporates the context path if any. 043 * 044 * @param assetPath default asset path 045 * @return a URI that can be sent to the client 046 */ 047 String convertAssetPath(String assetPath); 048}