Source Code Cross Referenced for AssetDispatcher.java in  » Library » Tapestry » org » apache » tapestry » internal » services » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Library » Tapestry » org.apache.tapestry.internal.services 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        // Copyright 2006 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:
015:        package org.apache.tapestry.internal.services;
016:
017:        import java.io.IOException;
018:        import java.net.URL;
019:
020:        import javax.servlet.http.HttpServletResponse;
021:
022:        import org.apache.tapestry.TapestryConstants;
023:        import org.apache.tapestry.ioc.Resource;
024:        import org.apache.tapestry.ioc.internal.util.ClasspathResource;
025:        import org.apache.tapestry.services.ClasspathAssetAliasManager;
026:        import org.apache.tapestry.services.Dispatcher;
027:        import org.apache.tapestry.services.Request;
028:        import org.apache.tapestry.services.Response;
029:
030:        /**
031:         * Recognizes requests where the path begins with "/asset/" and delivers the content therein as a
032:         * bytestream. Also handles requests that are simply polling for a change to the file.
033:         * 
034:         * @see ResourceStreamer
035:         * @see ClasspathAssetAliasManager
036:         * @see ResourceCache
037:         */
038:        public class AssetDispatcher implements  Dispatcher {
039:            private final ResourceStreamer _streamer;
040:
041:            private final ClasspathAssetAliasManager _aliasManager;
042:
043:            private final ResourceCache _resourceCache;
044:
045:            static final String IF_MODIFIED_SINCE_HEADER = "If-Modified-Since";
046:
047:            public AssetDispatcher(ResourceStreamer streamer,
048:                    ClasspathAssetAliasManager aliasManager,
049:                    ResourceCache resourceCache) {
050:                _streamer = streamer;
051:                _aliasManager = aliasManager;
052:                _resourceCache = resourceCache;
053:            }
054:
055:            public boolean dispatch(Request request, Response response)
056:                    throws IOException {
057:                String path = request.getPath();
058:
059:                // Remember that the request path does not include the context path, so we can simply start
060:                // looking for the asset path prefix right off the bat.
061:
062:                if (!path.startsWith(TapestryConstants.ASSET_PATH_PREFIX))
063:                    return false;
064:
065:                // ClassLoaders like their paths to start with a leading slash.
066:
067:                String resourcePath = _aliasManager.toResourcePath(path);
068:
069:                Resource resource = findResourceAndValidateDigest(response,
070:                        resourcePath);
071:
072:                if (resource == null)
073:                    return true;
074:
075:                URL url = resource.toURL();
076:
077:                if (url == null) {
078:                    response.sendError(HttpServletResponse.SC_NOT_FOUND,
079:                            ServicesMessages.assetDoesNotExist(resource));
080:                    return true;
081:                }
082:
083:                long ifModifiedSince = request
084:                        .getDateHeader(IF_MODIFIED_SINCE_HEADER);
085:                if (ifModifiedSince > 0) {
086:                    long modified = _resourceCache.getTimeModified(resource);
087:                    if (ifModifiedSince >= modified) {
088:                        response.sendError(HttpServletResponse.SC_NOT_MODIFIED,
089:                                "");
090:                        return true;
091:                    }
092:                }
093:
094:                _streamer.streamResource(resource);
095:
096:                return true;
097:            }
098:
099:            /**
100:             * @param response
101:             *            used to send errors back to the client
102:             * @param resourcePath
103:             *            the path to the requested resource, from the request
104:             * @return the resource for the path, with the digest stripped out of the URL, or null if the
105:             *         digest is invalid (and an error has been sent back to the client)
106:             * @throws IOException
107:             */
108:            private Resource findResourceAndValidateDigest(Response response,
109:                    String resourcePath) throws IOException {
110:                Resource resource = new ClasspathResource(resourcePath);
111:
112:                if (!_resourceCache.requiresDigest(resource))
113:                    return resource;
114:
115:                String file = resource.getFile();
116:
117:                // Somehow this code got real ugly, but it's all about preventing NPEs when a resource
118:                // that should have a digest doesn't.
119:
120:                boolean valid = false;
121:                Resource result = resource;
122:
123:                int lastdotx = file.lastIndexOf('.');
124:
125:                if (lastdotx > 0) {
126:                    int prevdotx = file.lastIndexOf('.', lastdotx - 1);
127:
128:                    if (prevdotx > 0) {
129:
130:                        String requestDigest = file.substring(prevdotx + 1,
131:                                lastdotx);
132:
133:                        // Strip the digest out of the file name.
134:
135:                        String realFile = file.substring(0, prevdotx)
136:                                + file.substring(lastdotx);
137:
138:                        result = resource.forFile(realFile);
139:
140:                        String actualDigest = _resourceCache.getDigest(result);
141:
142:                        valid = requestDigest.equals(actualDigest);
143:                    }
144:                }
145:
146:                if (!valid) {
147:                    response.sendError(HttpServletResponse.SC_FORBIDDEN,
148:                            ServicesMessages.wrongAssetDigest(result));
149:                    result = null;
150:                }
151:
152:                return result;
153:            }
154:        }
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