1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the 7 * "License"); you may not use this file except in compliance 8 * with the License. You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, 13 * software distributed under the License is distributed on an 14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 15 * KIND, either express or implied. See the License for the 16 * specific language governing permissions and limitations 17 * under the License. 18 * 19 */ 20 package org.apache.mina.core.filterchain; 21 22 import org.apache.mina.core.service.IoHandler; 23 import org.apache.mina.core.session.IdleStatus; 24 import org.apache.mina.core.session.IoSession; 25 import org.apache.mina.core.write.WriteRequest; 26 import org.apache.mina.filter.util.ReferenceCountingFilter; 27 28 /** 29 * A filter which intercepts {@link IoHandler} events like Servlet 30 * filters. Filters can be used for these purposes: 31 * <ul> 32 * <li>Event logging,</li> 33 * <li>Performance measurement,</li> 34 * <li>Authorization,</li> 35 * <li>Overload control,</li> 36 * <li>Message transformation (e.g. encryption and decryption, ...),</li> 37 * <li>and many more.</li> 38 * </ul> 39 * <p> 40 * <strong>Please NEVER implement your filters to wrap 41 * {@link IoSession}s.</strong> Users can cache the reference to the 42 * session, which might malfunction if any filters are added or removed later. 43 * 44 * <h3>The Life Cycle</h3> 45 * {@link IoFilter}s are activated only when they are inside {@link IoFilterChain}. 46 * <p> 47 * When you add an {@link IoFilter} to an {@link IoFilterChain}: 48 * <ol> 49 * <li>{@link #init()} is invoked by {@link ReferenceCountingFilter} if 50 * the filter is added at the first time.</li> 51 * <li>{@link #onPreAdd(IoFilterChain, String, NextFilter)} is invoked to notify 52 * that the filter will be added to the chain.</li> 53 * <li>The filter is added to the chain, and all events and I/O requests 54 * pass through the filter from now.</li> 55 * <li>{@link #onPostAdd(IoFilterChain, String, NextFilter)} is invoked to notify 56 * that the filter is added to the chain.</li> 57 * <li>The filter is removed from the chain if {@link #onPostAdd(IoFilterChain, String, org.apache.mina.core.filterchain.IoFilter.NextFilter)} 58 * threw an exception. {@link #destroy()} is also invoked by 59 * {@link ReferenceCountingFilter} if the filter is the last filter which 60 * was added to {@link IoFilterChain}s.</li> 61 * </ol> 62 * <p> 63 * When you remove an {@link IoFilter} from an {@link IoFilterChain}: 64 * <ol> 65 * <li>{@link #onPreRemove(IoFilterChain, String, NextFilter)} is invoked to 66 * notify that the filter will be removed from the chain.</li> 67 * <li>The filter is removed from the chain, and any events and I/O requests 68 * don't pass through the filter from now.</li> 69 * <li>{@link #onPostRemove(IoFilterChain, String, NextFilter)} is invoked to 70 * notify that the filter is removed from the chain.</li> 71 * <li>{@link #destroy()} is invoked by {@link ReferenceCountingFilter} if 72 * the removed filter was the last one.</li> 73 * </ol> 74 * 75 * @author <a href="http://mina.apache.org">Apache MINA Project</a> 76 * 77 * @see IoFilterAdapter 78 */ 79 public interface IoFilter { 80 /** 81 * Invoked by {@link ReferenceCountingFilter} when this filter 82 * is added to a {@link IoFilterChain} at the first time, so you can 83 * initialize shared resources. Please note that this method is never 84 * called if you don't wrap a filter with {@link ReferenceCountingFilter}. 85 */ 86 void init() throws Exception; 87 88 /** 89 * Invoked by {@link ReferenceCountingFilter} when this filter 90 * is not used by any {@link IoFilterChain} anymore, so you can destroy 91 * shared resources. Please note that this method is never called if 92 * you don't wrap a filter with {@link ReferenceCountingFilter}. 93 */ 94 void destroy() throws Exception; 95 96 /** 97 * Invoked before this filter is added to the specified <tt>parent</tt>. 98 * Please note that this method can be invoked more than once if 99 * this filter is added to more than one parents. This method is not 100 * invoked before {@link #init()} is invoked. 101 * 102 * @param parent the parent who called this method 103 * @param name the name assigned to this filter 104 * @param nextFilter the {@link NextFilter} for this filter. You can reuse 105 * this object until this filter is removed from the chain. 106 */ 107 void onPreAdd(IoFilterChain parent, String name, NextFilter nextFilter) throws Exception; 108 109 /** 110 * Invoked after this filter is added to the specified <tt>parent</tt>. 111 * Please note that this method can be invoked more than once if 112 * this filter is added to more than one parents. This method is not 113 * invoked before {@link #init()} is invoked. 114 * 115 * @param parent the parent who called this method 116 * @param name the name assigned to this filter 117 * @param nextFilter the {@link NextFilter} for this filter. You can reuse 118 * this object until this filter is removed from the chain. 119 */ 120 void onPostAdd(IoFilterChain parent, String name, NextFilter nextFilter) throws Exception; 121 122 /** 123 * Invoked before this filter is removed from the specified <tt>parent</tt>. 124 * Please note that this method can be invoked more than once if 125 * this filter is removed from more than one parents. 126 * This method is always invoked before {@link #destroy()} is invoked. 127 * 128 * @param parent the parent who called this method 129 * @param name the name assigned to this filter 130 * @param nextFilter the {@link NextFilter} for this filter. You can reuse 131 * this object until this filter is removed from the chain. 132 */ 133 void onPreRemove(IoFilterChain parent, String name, NextFilter nextFilter) throws Exception; 134 135 /** 136 * Invoked after this filter is removed from the specified <tt>parent</tt>. 137 * Please note that this method can be invoked more than once if 138 * this filter is removed from more than one parents. 139 * This method is always invoked before {@link #destroy()} is invoked. 140 * 141 * @param parent the parent who called this method 142 * @param name the name assigned to this filter 143 * @param nextFilter the {@link NextFilter} for this filter. You can reuse 144 * this object until this filter is removed from the chain. 145 */ 146 void onPostRemove(IoFilterChain parent, String name, NextFilter nextFilter) throws Exception; 147 148 /** 149 * Filters {@link IoHandler#sessionCreated(IoSession)} event. 150 */ 151 void sessionCreated(NextFilter nextFilter, IoSession session) throws Exception; 152 153 /** 154 * Filters {@link IoHandler#sessionOpened(IoSession)} event. 155 */ 156 void sessionOpened(NextFilter nextFilter, IoSession session) throws Exception; 157 158 /** 159 * Filters {@link IoHandler#sessionClosed(IoSession)} event. 160 */ 161 void sessionClosed(NextFilter nextFilter, IoSession session) throws Exception; 162 163 /** 164 * Filters {@link IoHandler#sessionIdle(IoSession,IdleStatus)} 165 * event. 166 */ 167 void sessionIdle(NextFilter nextFilter, IoSession session, IdleStatus status) throws Exception; 168 169 /** 170 * Filters {@link IoHandler#exceptionCaught(IoSession,Throwable)} 171 * event. 172 */ 173 void exceptionCaught(NextFilter nextFilter, IoSession session, Throwable cause) throws Exception; 174 175 /** 176 * Filters {@link IoHandler#messageReceived(IoSession,Object)} 177 * event. 178 */ 179 void messageReceived(NextFilter nextFilter, IoSession session, Object message) throws Exception; 180 181 /** 182 * Filters {@link IoHandler#messageSent(IoSession,Object)} 183 * event. 184 */ 185 void messageSent(NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws Exception; 186 187 /** 188 * Filters {@link IoSession#close()} method invocation. 189 */ 190 void filterClose(NextFilter nextFilter, IoSession session) throws Exception; 191 192 /** 193 * Filters {@link IoSession#write(Object)} method invocation. 194 */ 195 void filterWrite(NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws Exception; 196 197 /** 198 * Represents the next {@link IoFilter} in {@link IoFilterChain}. 199 */ 200 public interface NextFilter { 201 /** 202 * Forwards <tt>sessionCreated</tt> event to next filter. 203 */ 204 void sessionCreated(IoSession session); 205 206 /** 207 * Forwards <tt>sessionOpened</tt> event to next filter. 208 */ 209 void sessionOpened(IoSession session); 210 211 /** 212 * Forwards <tt>sessionClosed</tt> event to next filter. 213 */ 214 void sessionClosed(IoSession session); 215 216 /** 217 * Forwards <tt>sessionIdle</tt> event to next filter. 218 */ 219 void sessionIdle(IoSession session, IdleStatus status); 220 221 /** 222 * Forwards <tt>exceptionCaught</tt> event to next filter. 223 */ 224 void exceptionCaught(IoSession session, Throwable cause); 225 226 /** 227 * Forwards <tt>messageReceived</tt> event to next filter. 228 */ 229 void messageReceived(IoSession session, Object message); 230 231 /** 232 * Forwards <tt>messageSent</tt> event to next filter. 233 */ 234 void messageSent(IoSession session, WriteRequest writeRequest); 235 236 /** 237 * Forwards <tt>filterWrite</tt> event to next filter. 238 */ 239 void filterWrite(IoSession session, WriteRequest writeRequest); 240 241 /** 242 * Forwards <tt>filterClose</tt> event to next filter. 243 */ 244 void filterClose(IoSession session); 245 246 } 247 }