001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018
019 package compressionFilters;
020
021 import java.io.IOException;
022 import java.util.Enumeration;
023
024 import javax.servlet.Filter;
025 import javax.servlet.FilterChain;
026 import javax.servlet.FilterConfig;
027 import javax.servlet.ServletException;
028 import javax.servlet.ServletRequest;
029 import javax.servlet.ServletResponse;
030 import javax.servlet.http.HttpServletRequest;
031 import javax.servlet.http.HttpServletResponse;
032
033
034 /**
035 * Implementation of <code>javax.servlet.Filter</code> used to compress
036 * the ServletResponse if it is bigger than a threshold.
037 *
038 * @author Amy Roh
039 * @author Dmitri Valdin
040 * @version $Revision: 664175 $, $Date: 2008-06-06 18:43:44 -0400 (Fri, 06 Jun 2008) $
041 */
042
043 public class CompressionFilter implements Filter {
044
045 /**
046 * The filter configuration object we are associated with. If this value
047 * is null, this filter instance is not currently configured.
048 */
049 private FilterConfig config = null;
050
051 /**
052 * Minimal reasonable threshold
053 */
054 private int minThreshold = 128;
055
056
057 /**
058 * The threshold number to compress
059 */
060 protected int compressionThreshold;
061
062 /**
063 * Debug level for this filter
064 */
065 private int debug = 0;
066
067 /**
068 * Place this filter into service.
069 *
070 * @param filterConfig The filter configuration object
071 */
072
073 public void init(FilterConfig filterConfig) {
074
075 config = filterConfig;
076 if (filterConfig != null) {
077 String value = filterConfig.getInitParameter("debug");
078 if (value != null) {
079 debug = Integer.parseInt(value);
080 } else {
081 debug = 0;
082 }
083 String str = filterConfig.getInitParameter("compressionThreshold");
084 if (str != null) {
085 compressionThreshold = Integer.parseInt(str);
086 if (compressionThreshold != 0 && compressionThreshold < minThreshold) {
087 if (debug > 0) {
088 System.out.println("compressionThreshold should be either 0 - no compression or >= " + minThreshold);
089 System.out.println("compressionThreshold set to " + minThreshold);
090 }
091 compressionThreshold = minThreshold;
092 }
093 } else {
094 compressionThreshold = 0;
095 }
096
097 } else {
098 compressionThreshold = 0;
099 }
100
101 }
102
103 /**
104 * Take this filter out of service.
105 */
106 public void destroy() {
107
108 this.config = null;
109
110 }
111
112 /**
113 * The <code>doFilter</code> method of the Filter is called by the container
114 * each time a request/response pair is passed through the chain due
115 * to a client request for a resource at the end of the chain.
116 * The FilterChain passed into this method allows the Filter to pass on the
117 * request and response to the next entity in the chain.<p>
118 * This method first examines the request to check whether the client support
119 * compression. <br>
120 * It simply just pass the request and response if there is no support for
121 * compression.<br>
122 * If the compression support is available, it creates a
123 * CompressionServletResponseWrapper object which compresses the content and
124 * modifies the header if the content length is big enough.
125 * It then invokes the next entity in the chain using the FilterChain object
126 * (<code>chain.doFilter()</code>), <br>
127 */
128
129 public void doFilter(ServletRequest request, ServletResponse response,
130 FilterChain chain) throws IOException, ServletException {
131
132 if (debug > 0) {
133 System.out.println("@doFilter");
134 }
135
136 if (compressionThreshold == 0) {
137 if (debug > 0) {
138 System.out.println("doFilter gets called, but compressionTreshold is set to 0 - no compression");
139 }
140 chain.doFilter(request, response);
141 return;
142 }
143
144 boolean supportCompression = false;
145 if (request instanceof HttpServletRequest) {
146 if (debug > 1) {
147 System.out.println("requestURI = " + ((HttpServletRequest) request).getRequestURI());
148 }
149
150 // Are we allowed to compress ?
151 String s = (String) ((HttpServletRequest) request).getParameter("gzip");
152 if ("false".equals(s)) {
153 if (debug > 0) {
154 System.out.println("got parameter gzip=false --> don't compress, just chain filter");
155 }
156 chain.doFilter(request, response);
157 return;
158 }
159
160 Enumeration e =
161 ((HttpServletRequest) request).getHeaders("Accept-Encoding");
162 while (e.hasMoreElements()) {
163 String name = (String) e.nextElement();
164 if (name.indexOf("gzip") != -1) {
165 if (debug > 0) {
166 System.out.println("supports compression");
167 }
168 supportCompression = true;
169 } else {
170 if (debug > 0) {
171 System.out.println("no support for compresion");
172 }
173 }
174 }
175 }
176
177 if (!supportCompression) {
178 if (debug > 0) {
179 System.out.println("doFilter gets called wo compression");
180 }
181 chain.doFilter(request, response);
182 return;
183 } else {
184 if (response instanceof HttpServletResponse) {
185 CompressionServletResponseWrapper wrappedResponse =
186 new CompressionServletResponseWrapper((HttpServletResponse) response);
187 wrappedResponse.setDebugLevel(debug);
188 wrappedResponse.setCompressionThreshold(compressionThreshold);
189 if (debug > 0) {
190 System.out.println("doFilter gets called with compression");
191 }
192 try {
193 chain.doFilter(request, wrappedResponse);
194 } finally {
195 wrappedResponse.finishResponse();
196 }
197 return;
198 }
199 }
200 }
201
202 /**
203 * Set filter config
204 * This function is equivalent to init. Required by Weblogic 6.1
205 *
206 * @param filterConfig The filter configuration object
207 */
208 public void setFilterConfig(FilterConfig filterConfig) {
209 init(filterConfig);
210 }
211
212 /**
213 * Return filter config
214 * Required by Weblogic 6.1
215 */
216 public FilterConfig getFilterConfig() {
217 return config;
218 }
219
220 }
221