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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.filter.util;
21  
22  import org.apache.mina.core.filterchain.IoFilter;
23  import org.apache.mina.core.filterchain.IoFilterAdapter;
24  import org.apache.mina.core.filterchain.IoFilterChain;
25  import org.apache.mina.core.session.IdleStatus;
26  import org.apache.mina.core.session.IoSession;
27  import org.apache.mina.core.write.WriteRequest;
28  
29  /**
30   * An {@link IoFilter}s wrapper that keeps track of the number of usages of this filter and will call init/destroy
31   * when the filter is not in use.
32   *
33   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
34   * @org.apache.xbean.XBean
35   */
36  public class ReferenceCountingFilter extends IoFilterAdapter {
37      private final IoFilter filter;
38  
39      private int count = 0;
40  
41      public ReferenceCountingFilter(IoFilter filter) {
42          this.filter = filter;
43      }
44  
45      public void init() throws Exception {
46          // no-op, will init on-demand in pre-add if count == 0
47      }
48  
49      public void destroy() throws Exception {
50          //no-op, will destroy on-demand in post-remove if count == 0
51      }
52  
53      public synchronized void onPreAdd(IoFilterChain parent, String name, NextFilter nextFilter) throws Exception {
54          if (0 == count) {
55              filter.init();
56          }
57  
58          ++count;
59  
60          filter.onPreAdd(parent, name, nextFilter);
61      }
62  
63      public synchronized void onPostRemove(IoFilterChain parent, String name, NextFilter nextFilter) throws Exception {
64          filter.onPostRemove(parent, name, nextFilter);
65  
66          --count;
67  
68          if (0 == count) {
69              filter.destroy();
70          }
71      }
72  
73      public void exceptionCaught(NextFilter nextFilter, IoSession session, Throwable cause) throws Exception {
74          filter.exceptionCaught(nextFilter, session, cause);
75      }
76  
77      public void filterClose(NextFilter nextFilter, IoSession session) throws Exception {
78          filter.filterClose(nextFilter, session);
79      }
80  
81      public void filterWrite(NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws Exception {
82          filter.filterWrite(nextFilter, session, writeRequest);
83      }
84  
85      public void messageReceived(NextFilter nextFilter, IoSession session, Object message) throws Exception {
86          filter.messageReceived(nextFilter, session, message);
87      }
88  
89      public void messageSent(NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws Exception {
90          filter.messageSent(nextFilter, session, writeRequest);
91      }
92  
93      public void onPostAdd(IoFilterChain parent, String name, NextFilter nextFilter) throws Exception {
94          filter.onPostAdd(parent, name, nextFilter);
95      }
96  
97      public void onPreRemove(IoFilterChain parent, String name, NextFilter nextFilter) throws Exception {
98          filter.onPreRemove(parent, name, nextFilter);
99      }
100 
101     public void sessionClosed(NextFilter nextFilter, IoSession session) throws Exception {
102         filter.sessionClosed(nextFilter, session);
103     }
104 
105     public void sessionCreated(NextFilter nextFilter, IoSession session) throws Exception {
106         filter.sessionCreated(nextFilter, session);
107     }
108 
109     public void sessionIdle(NextFilter nextFilter, IoSession session, IdleStatus status) throws Exception {
110         filter.sessionIdle(nextFilter, session, status);
111     }
112 
113     public void sessionOpened(NextFilter nextFilter, IoSession session) throws Exception {
114         filter.sessionOpened(nextFilter, session);
115     }
116 }