1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 package compressionFilters;
19
20 import java.io.IOException;
21 import java.util.Enumeration;
22
23 import javax.servlet.Filter;
24 import javax.servlet.FilterChain;
25 import javax.servlet.FilterConfig;
26 import javax.servlet.ServletException;
27 import javax.servlet.ServletRequest;
28 import javax.servlet.ServletResponse;
29 import javax.servlet.http.HttpServletRequest;
30 import javax.servlet.http.HttpServletResponse;
31
32
33 /**
34 * Implementation of <code>javax.servlet.Filter</code> used to compress
35 * the ServletResponse if it is bigger than a threshold.
36 *
37 * @author Amy Roh
38 * @author Dmitri Valdin
39 * @version $Revision: 664175 $, $Date: 2008-06-06 18:43:44 -0400 (Fri, 06 Jun 2008) $
40 */
41
42 public class CompressionFilter implements Filter {
43
44 /**
45 * The filter configuration object we are associated with. If this value
46 * is null, this filter instance is not currently configured.
47 */
48 private FilterConfig config = null;
49
50 /**
51 * Minimal reasonable threshold
52 */
53 private int minThreshold = 128;
54
55
56 /**
57 * The threshold number to compress
58 */
59 protected int compressionThreshold;
60
61 /**
62 * Debug level for this filter
63 */
64 private int debug = 0;
65
66 /**
67 * Place this filter into service.
68 *
69 * @param filterConfig The filter configuration object
70 */
71
72 public void init(FilterConfig filterConfig) {
73
74 config = filterConfig;
75 if (filterConfig != null) {
76 String value = filterConfig.getInitParameter("debug");
77 if (value != null) {
78 debug = Integer.parseInt(value);
79 } else {
80 debug = 0;
81 }
82 String str = filterConfig.getInitParameter("compressionThreshold");
83 if (str != null) {
84 compressionThreshold = Integer.parseInt(str);
85 if (compressionThreshold != 0 && compressionThreshold < minThreshold) {
86 if (debug > 0) {
87 System.out.println("compressionThreshold should be either 0 - no compression or >= " + minThreshold);
88 System.out.println("compressionThreshold set to " + minThreshold);
89 }
90 compressionThreshold = minThreshold;
91 }
92 } else {
93 compressionThreshold = 0;
94 }
95
96 } else {
97 compressionThreshold = 0;
98 }
99
100 }
101
102 /**
103 * Take this filter out of service.
104 */
105 public void destroy() {
106
107 this.config = null;
108
109 }
110
111 /**
112 * The <code>doFilter</code> method of the Filter is called by the container
113 * each time a request/response pair is passed through the chain due
114 * to a client request for a resource at the end of the chain.
115 * The FilterChain passed into this method allows the Filter to pass on the
116 * request and response to the next entity in the chain.<p>
117 * This method first examines the request to check whether the client support
118 * compression. <br>
119 * It simply just pass the request and response if there is no support for
120 * compression.<br>
121 * If the compression support is available, it creates a
122 * CompressionServletResponseWrapper object which compresses the content and
123 * modifies the header if the content length is big enough.
124 * It then invokes the next entity in the chain using the FilterChain object
125 * (<code>chain.doFilter()</code>), <br>
126 */
127
128 public void doFilter(ServletRequest request, ServletResponse response,
129 FilterChain chain) throws IOException, ServletException {
130
131 if (debug > 0) {
132 System.out.println("@doFilter");
133 }
134
135 if (compressionThreshold == 0) {
136 if (debug > 0) {
137 System.out.println("doFilter gets called, but compressionTreshold is set to 0 - no compression");
138 }
139 chain.doFilter(request, response);
140 return;
141 }
142
143 boolean supportCompression = false;
144 if (request instanceof HttpServletRequest) {
145 if (debug > 1) {
146 System.out.println("requestURI = " + ((HttpServletRequest) request).getRequestURI());
147 }
148
149 // Are we allowed to compress ?
150 String s = (String) ((HttpServletRequest) request).getParameter("gzip");
151 if ("false".equals(s)) {
152 if (debug > 0) {
153 System.out.println("got parameter gzip=false --> don't compress, just chain filter");
154 }
155 chain.doFilter(request, response);
156 return;
157 }
158
159 Enumeration e =
160 ((HttpServletRequest) request).getHeaders("Accept-Encoding");
161 while (e.hasMoreElements()) {
162 String name = (String) e.nextElement();
163 if (name.indexOf("gzip") != -1) {
164 if (debug > 0) {
165 System.out.println("supports compression");
166 }
167 supportCompression = true;
168 } else {
169 if (debug > 0) {
170 System.out.println("no support for compresion");
171 }
172 }
173 }
174 }
175
176 if (!supportCompression) {
177 if (debug > 0) {
178 System.out.println("doFilter gets called wo compression");
179 }
180 chain.doFilter(request, response);
181 return;
182 } else {
183 if (response instanceof HttpServletResponse) {
184 CompressionServletResponseWrapper wrappedResponse =
185 new CompressionServletResponseWrapper((HttpServletResponse) response);
186 wrappedResponse.setDebugLevel(debug);
187 wrappedResponse.setCompressionThreshold(compressionThreshold);
188 if (debug > 0) {
189 System.out.println("doFilter gets called with compression");
190 }
191 try {
192 chain.doFilter(request, wrappedResponse);
193 } finally {
194 wrappedResponse.finishResponse();
195 }
196 return;
197 }
198 }
199 }
200
201 /**
202 * Set filter config
203 * This function is equivalent to init. Required by Weblogic 6.1
204 *
205 * @param filterConfig The filter configuration object
206 */
207 public void setFilterConfig(FilterConfig filterConfig) {
208 init(filterConfig);
209 }
210
211 /**
212 * Return filter config
213 * Required by Weblogic 6.1
214 */
215 public FilterConfig getFilterConfig() {
216 return config;
217 }
218
219 }
220