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18 package compressionFilters;
19
20 import java.io.IOException;
21 import java.util.Enumeration;
22 import javax.servlet.Filter;
23 import javax.servlet.FilterChain;
24 import javax.servlet.FilterConfig;
25 import javax.servlet.ServletException;
26 import javax.servlet.ServletRequest;
27 import javax.servlet.ServletResponse;
28 import javax.servlet.http.HttpServletRequest;
29 import javax.servlet.http.HttpServletResponse;
30
31
32 /**
33 * Implementation of <code>javax.servlet.Filter</code> used to compress
34 * the ServletResponse if it is bigger than a threshold.
35 *
36 * @author Amy Roh
37 * @author Dmitri Valdin
38 * @version $Revision: 267129 $, $Date: 2004-03-18 08:40:35 -0800 (Thu, 18 Mar 2004) $
39 */
40
41 public class CompressionFilter implements Filter{
42
43 /**
44 * The filter configuration object we are associated with. If this value
45 * is null, this filter instance is not currently configured.
46 */
47 private FilterConfig config = null;
48
49 /**
50 * Minimal reasonable threshold
51 */
52 private int minThreshold = 128;
53
54
55 /**
56 * The threshold number to compress
57 */
58 protected int compressionThreshold;
59
60 /**
61 * Debug level for this filter
62 */
63 private int debug = 0;
64
65 /**
66 * Place this filter into service.
67 *
68 * @param filterConfig The filter configuration object
69 */
70
71 public void init(FilterConfig filterConfig) {
72
73 config = filterConfig;
74 if (filterConfig != null) {
75 String value = filterConfig.getInitParameter("debug");
76 if (value!=null) {
77 debug = Integer.parseInt(value);
78 } else {
79 debug = 0;
80 }
81 String str = filterConfig.getInitParameter("compressionThreshold");
82 if (str!=null) {
83 compressionThreshold = Integer.parseInt(str);
84 if (compressionThreshold != 0 && compressionThreshold < minThreshold) {
85 if (debug > 0) {
86 System.out.println("compressionThreshold should be either 0 - no compression or >= " + minThreshold);
87 System.out.println("compressionThreshold set to " + minThreshold);
88 }
89 compressionThreshold = minThreshold;
90 }
91 } else {
92 compressionThreshold = 0;
93 }
94
95 } else {
96 compressionThreshold = 0;
97 }
98
99 }
100
101 /**
102 * Take this filter out of service.
103 */
104 public void destroy() {
105
106 this.config = null;
107
108 }
109
110 /**
111 * The <code>doFilter</code> method of the Filter is called by the container
112 * each time a request/response pair is passed through the chain due
113 * to a client request for a resource at the end of the chain.
114 * The FilterChain passed into this method allows the Filter to pass on the
115 * request and response to the next entity in the chain.<p>
116 * This method first examines the request to check whether the client support
117 * compression. <br>
118 * It simply just pass the request and response if there is no support for
119 * compression.<br>
120 * If the compression support is available, it creates a
121 * CompressionServletResponseWrapper object which compresses the content and
122 * modifies the header if the content length is big enough.
123 * It then invokes the next entity in the chain using the FilterChain object
124 * (<code>chain.doFilter()</code>), <br>
125 **/
126
127 public void doFilter ( ServletRequest request, ServletResponse response,
128 FilterChain chain ) throws IOException, ServletException {
129
130 if (debug > 0) {
131 System.out.println("@doFilter");
132 }
133
134 if (compressionThreshold == 0) {
135 if (debug > 0) {
136 System.out.println("doFilter gets called, but compressionTreshold is set to 0 - no compression");
137 }
138 chain.doFilter(request, response);
139 return;
140 }
141
142 boolean supportCompression = false;
143 if (request instanceof HttpServletRequest) {
144 if (debug > 1) {
145 System.out.println("requestURI = " + ((HttpServletRequest)request).getRequestURI());
146 }
147
148
149 String s = (String) ((HttpServletRequest)request).getParameter("gzip");
150 if ("false".equals(s)) {
151 if (debug > 0) {
152 System.out.println("got parameter gzip=false --> don't compress, just chain filter");
153 }
154 chain.doFilter(request, response);
155 return;
156 }
157
158 Enumeration e =
159 ((HttpServletRequest)request).getHeaders("Accept-Encoding");
160 while (e.hasMoreElements()) {
161 String name = (String)e.nextElement();
162 if (name.indexOf("gzip") != -1) {
163 if (debug > 0) {
164 System.out.println("supports compression");
165 }
166 supportCompression = true;
167 } else {
168 if (debug > 0) {
169 System.out.println("no support for compresion");
170 }
171 }
172 }
173 }
174
175 if (!supportCompression) {
176 if (debug > 0) {
177 System.out.println("doFilter gets called wo compression");
178 }
179 chain.doFilter(request, response);
180 return;
181 } else {
182 if (response instanceof HttpServletResponse) {
183 CompressionServletResponseWrapper wrappedResponse =
184 new CompressionServletResponseWrapper((HttpServletResponse)response);
185 wrappedResponse.setDebugLevel(debug);
186 wrappedResponse.setCompressionThreshold(compressionThreshold);
187 if (debug > 0) {
188 System.out.println("doFilter gets called with compression");
189 }
190 try {
191 chain.doFilter(request, wrappedResponse);
192 } finally {
193 wrappedResponse.finishResponse();
194 }
195 return;
196 }
197 }
198 }
199
200 /**
201 * Set filter config
202 * This function is equivalent to init. Required by Weblogic 6.1
203 *
204 * @param filterConfig The filter configuration object
205 */
206 public void setFilterConfig(FilterConfig filterConfig) {
207 init(filterConfig);
208 }
209
210 /**
211 * Return filter config
212 * Required by Weblogic 6.1
213 */
214 public FilterConfig getFilterConfig() {
215 return config;
216 }
217
218 }
219