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