001 /*
002 * Copyright 2004 The Apache Software Foundation
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017 package compressionFilters;
018
019 import java.io.IOException;
020 import java.util.Enumeration;
021 import javax.servlet.Filter;
022 import javax.servlet.FilterChain;
023 import javax.servlet.FilterConfig;
024 import javax.servlet.ServletException;
025 import javax.servlet.ServletRequest;
026 import javax.servlet.ServletResponse;
027 import javax.servlet.http.HttpServletRequest;
028 import javax.servlet.http.HttpServletResponse;
029
030
031 /**
032 * Implementation of <code>javax.servlet.Filter</code> used to compress
033 * the ServletResponse if it is bigger than a threshold.
034 *
035 * @author Amy Roh
036 * @author Dmitri Valdin
037 * @version $Revision: 267129 $, $Date: 2004-03-18 08:40:35 -0800 (Thu, 18 Mar 2004) $
038 */
039
040 public class CompressionFilter implements Filter{
041
042 /**
043 * The filter configuration object we are associated with. If this value
044 * is null, this filter instance is not currently configured.
045 */
046 private FilterConfig config = null;
047
048 /**
049 * Minimal reasonable threshold
050 */
051 private int minThreshold = 128;
052
053
054 /**
055 * The threshold number to compress
056 */
057 protected int compressionThreshold;
058
059 /**
060 * Debug level for this filter
061 */
062 private int debug = 0;
063
064 /**
065 * Place this filter into service.
066 *
067 * @param filterConfig The filter configuration object
068 */
069
070 public void init(FilterConfig filterConfig) {
071
072 config = filterConfig;
073 if (filterConfig != null) {
074 String value = filterConfig.getInitParameter("debug");
075 if (value!=null) {
076 debug = Integer.parseInt(value);
077 } else {
078 debug = 0;
079 }
080 String str = filterConfig.getInitParameter("compressionThreshold");
081 if (str!=null) {
082 compressionThreshold = Integer.parseInt(str);
083 if (compressionThreshold != 0 && compressionThreshold < minThreshold) {
084 if (debug > 0) {
085 System.out.println("compressionThreshold should be either 0 - no compression or >= " + minThreshold);
086 System.out.println("compressionThreshold set to " + minThreshold);
087 }
088 compressionThreshold = minThreshold;
089 }
090 } else {
091 compressionThreshold = 0;
092 }
093
094 } else {
095 compressionThreshold = 0;
096 }
097
098 }
099
100 /**
101 * Take this filter out of service.
102 */
103 public void destroy() {
104
105 this.config = null;
106
107 }
108
109 /**
110 * The <code>doFilter</code> method of the Filter is called by the container
111 * each time a request/response pair is passed through the chain due
112 * to a client request for a resource at the end of the chain.
113 * The FilterChain passed into this method allows the Filter to pass on the
114 * request and response to the next entity in the chain.<p>
115 * This method first examines the request to check whether the client support
116 * compression. <br>
117 * It simply just pass the request and response if there is no support for
118 * compression.<br>
119 * If the compression support is available, it creates a
120 * CompressionServletResponseWrapper object which compresses the content and
121 * modifies the header if the content length is big enough.
122 * It then invokes the next entity in the chain using the FilterChain object
123 * (<code>chain.doFilter()</code>), <br>
124 **/
125
126 public void doFilter ( ServletRequest request, ServletResponse response,
127 FilterChain chain ) throws IOException, ServletException {
128
129 if (debug > 0) {
130 System.out.println("@doFilter");
131 }
132
133 if (compressionThreshold == 0) {
134 if (debug > 0) {
135 System.out.println("doFilter gets called, but compressionTreshold is set to 0 - no compression");
136 }
137 chain.doFilter(request, response);
138 return;
139 }
140
141 boolean supportCompression = false;
142 if (request instanceof HttpServletRequest) {
143 if (debug > 1) {
144 System.out.println("requestURI = " + ((HttpServletRequest)request).getRequestURI());
145 }
146
147 // Are we allowed to compress ?
148 String s = (String) ((HttpServletRequest)request).getParameter("gzip");
149 if ("false".equals(s)) {
150 if (debug > 0) {
151 System.out.println("got parameter gzip=false --> don't compress, just chain filter");
152 }
153 chain.doFilter(request, response);
154 return;
155 }
156
157 Enumeration e =
158 ((HttpServletRequest)request).getHeaders("Accept-Encoding");
159 while (e.hasMoreElements()) {
160 String name = (String)e.nextElement();
161 if (name.indexOf("gzip") != -1) {
162 if (debug > 0) {
163 System.out.println("supports compression");
164 }
165 supportCompression = true;
166 } else {
167 if (debug > 0) {
168 System.out.println("no support for compresion");
169 }
170 }
171 }
172 }
173
174 if (!supportCompression) {
175 if (debug > 0) {
176 System.out.println("doFilter gets called wo compression");
177 }
178 chain.doFilter(request, response);
179 return;
180 } else {
181 if (response instanceof HttpServletResponse) {
182 CompressionServletResponseWrapper wrappedResponse =
183 new CompressionServletResponseWrapper((HttpServletResponse)response);
184 wrappedResponse.setDebugLevel(debug);
185 wrappedResponse.setCompressionThreshold(compressionThreshold);
186 if (debug > 0) {
187 System.out.println("doFilter gets called with compression");
188 }
189 try {
190 chain.doFilter(request, wrappedResponse);
191 } finally {
192 wrappedResponse.finishResponse();
193 }
194 return;
195 }
196 }
197 }
198
199 /**
200 * Set filter config
201 * This function is equivalent to init. Required by Weblogic 6.1
202 *
203 * @param filterConfig The filter configuration object
204 */
205 public void setFilterConfig(FilterConfig filterConfig) {
206 init(filterConfig);
207 }
208
209 /**
210 * Return filter config
211 * Required by Weblogic 6.1
212 */
213 public FilterConfig getFilterConfig() {
214 return config;
215 }
216
217 }
218