001// Copyright 2010 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.assets; 016 017import java.io.IOException; 018 019import javax.servlet.http.HttpServletResponse; 020 021import org.apache.tapestry5.Asset; 022import org.apache.tapestry5.SymbolConstants; 023import org.apache.tapestry5.internal.services.AssetDispatcher; 024import org.apache.tapestry5.services.Request; 025import org.apache.tapestry5.services.Response; 026 027/** 028 * Handler for asset requests, which expose some kind of {@link Asset} to 029 * the user agent (i.e., the client web browser). Starting in Tapestry 5.2, 030 * asset paths are more structured, consisting of four parts: 031 * <ul> 032 * <li><code>/assets/</code> -- the root path for all assets 033 * <li> 034 * <em>application version</em> -- the application version, as defined by the 035 * {@link SymbolConstants#APPLICATION_VERSION} symbol 036 * <li><em>handler id</em> -- a handler for this part of the asset path (defined by contributions to the 037 * <code>AssetDispatcher</code> service) 038 * <li><em>extra path</em> -- additional path beyond the handler id, used to identify the specific resource 039 * </ul> 040 * <p> 041 * So, an example path might be <code>/assets/1.0.1/corelib/components/select.png</code>. The handler id would be 042 * <code>corelib</code>, and the extra path would be <code>components/select.png</code>. 043 * 044 * @since 5.2.0 045 * @see AssetDispatcher 046 */ 047public interface AssetRequestHandler 048{ 049 /** 050 * Given a request targeted (via the handler id) to the specific handler, process the request. 051 * The handler is responsible for processing the request, sending back either a bytestream 052 * (via {@link Response#getOutputStream(String)}) or an error response 053 * (via {@link Response#sendError(int, String)}). It is the handler's responsibility to allow 054 * for client-side caching (possibly sending an {@link HttpServletResponse#SC_NOT_MODIFIED} response). 055 * <p> 056 * The handler should return true if it provided a response. If the handler returns false, this indicates that the 057 * extra path did not identify a known asset (virtual or otherwise) and the AssetDispatcher service should send a 058 * {@link HttpServletResponse#SC_NOT_FOUND} response. 059 * 060 * @param request 061 * incoming asset request 062 * @param response 063 * used to send a response to client 064 * @param extraPath 065 * additional path to identify the specific asset 066 * @return true if request handler, false if asset not found 067 */ 068 boolean handleAssetRequest(Request request, Response response, String extraPath) throws IOException; 069}