001// Copyright 2010, 2012, 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.assets; 016 017import org.apache.tapestry5.Asset; 018import org.apache.tapestry5.internal.services.AssetDispatcher; 019import org.apache.tapestry5.services.Request; 020import org.apache.tapestry5.services.Response; 021 022import javax.servlet.http.HttpServletResponse; 023import java.io.IOException; 024 025/** 026 * Handler for asset requests, which expose some kind of {@link Asset} to 027 * the user agent (i.e., the client web browser). When contributed to the {@link AssetDispatcher} service, 028 * the contributed key is a handler id (such as "meta/core"). 029 * <p/> 030 * An example request path might be <code>/assets/meta/core/dd8d73ac51dbab28caaec4865d302bf2/deselect.png</code>. 031 * The handler id would be 032 * <code>meta/core</code>, the {@linkplain AssetChecksumGenerator checksum of the resource content} is the 033 * hex string, and the extra path would be <code>select.png</code>. 034 * 035 * @see AssetDispatcher 036 * @see org.apache.tapestry5.services.AssetRequestDispatcher 037 * @see AssetPathConstructor 038 * @since 5.2.0 039 */ 040public interface AssetRequestHandler 041{ 042 /** 043 * Given a request targeted (via the handler id) to the specific handler, process the request. 044 * The handler is responsible for processing the request, sending back either a bytestream 045 * (via {@link Response#getOutputStream(String)}) or an error response 046 * (via {@link Response#sendError(int, String)}). It is the handler's responsibility to allow 047 * for client-side caching (possibly sending an {@link HttpServletResponse#SC_NOT_MODIFIED} response). 048 * <p/> 049 * The handler should return true if it provided a response. If the handler returns false, this indicates that the 050 * extra path did not identify a known asset (virtual or otherwise) and the AssetDispatcher service should send a 051 * {@link HttpServletResponse#SC_NOT_FOUND} response. 052 * <p/> 053 * Starting in Tapestry 5.4, the handler is informed by the {@link org.apache.tapestry5.services.AssetRequestDispatcher} 054 * whether or not the content should be compressed (this is determined based on information in the URL). 055 * 056 * @param request 057 * incoming asset request 058 * @param response 059 * used to send a response to client 060 * @param extraPath 061 * additional path to identify the specific asset 062 * @return true if request was handled (and response sent), false if asset not found 063 * @see org.apache.tapestry5.TapestryConstants#COMPRESS_CONTENT 064 */ 065 boolean handleAssetRequest(Request request, Response response, String extraPath) throws IOException; 066}