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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.session.IoEventType;
25  import org.apache.mina.core.session.IoSession;
26  import org.apache.mina.core.write.WriteRequest;
27  import org.apache.mina.core.write.WriteRequestWrapper;
28  
29  /**
30   * An abstract {@link IoFilter} that simplifies the implementation of
31   * an {@link IoFilter} that filters an {@link IoEventType#WRITE} event.
32   *
33   * @author The Apache MINA Project (dev@mina.apache.org)
34   * @version $Rev: 671827 $, $Date: 2008-06-26 10:49:48 +0200 (jeu, 26 jun 2008) $
35   *
36   */
37  public abstract class WriteRequestFilter extends IoFilterAdapter {
38  
39      @Override
40      public void exceptionCaught(NextFilter nextFilter, IoSession session,
41              Throwable cause) throws Exception {
42          nextFilter.exceptionCaught(session, cause);
43      }
44  
45      @Override
46      public void filterWrite(NextFilter nextFilter, IoSession session,
47              WriteRequest writeRequest) throws Exception {
48          Object filteredMessage = doFilterWrite(nextFilter, session, writeRequest);
49          if (filteredMessage != null && filteredMessage != writeRequest.getMessage()) {
50              nextFilter.filterWrite(
51                      session, new FilteredWriteRequest(
52                              filteredMessage, writeRequest));
53          } else {
54              nextFilter.filterWrite(session, writeRequest);
55          }
56      }
57  
58      @Override
59      public void messageSent(NextFilter nextFilter, IoSession session,
60              WriteRequest writeRequest) throws Exception {
61          if (writeRequest instanceof FilteredWriteRequest) {
62              FilteredWriteRequest req = (FilteredWriteRequest) writeRequest;
63              if (req.getParent() == this) {
64                  nextFilter.messageSent(session, req.getParentRequest());
65                  return;
66              }
67          }
68  
69          nextFilter.messageSent(session, writeRequest);
70      }
71  
72      protected abstract Object doFilterWrite(
73              NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws Exception;
74  
75      private class FilteredWriteRequest extends WriteRequestWrapper {
76          private final Object filteredMessage;
77  
78          public FilteredWriteRequest(Object filteredMessage, WriteRequest writeRequest) {
79              super(writeRequest);
80  
81              if (filteredMessage == null) {
82                  throw new NullPointerException("filteredMessage");
83              }
84              this.filteredMessage = filteredMessage;
85          }
86  
87          public WriteRequestFilter getParent() {
88              return WriteRequestFilter.this;
89          }
90  
91          @Override
92          public Object getMessage() {
93              return filteredMessage;
94          }
95      }
96  }