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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: 694335 $, $Date: 2008-09-11 18:20:42 +0200 (Thu, 11 Sep 2008) $
35   *
36   */
37  public abstract class WriteRequestFilter extends IoFilterAdapter {
38      @Override
39      public void filterWrite(NextFilter nextFilter, IoSession session,
40              WriteRequest writeRequest) throws Exception {
41          Object filteredMessage = doFilterWrite(nextFilter, session, writeRequest);
42          if (filteredMessage != null && filteredMessage != writeRequest.getMessage()) {
43              nextFilter.filterWrite(
44                      session, new FilteredWriteRequest(
45                              filteredMessage, writeRequest));
46          } else {
47              nextFilter.filterWrite(session, writeRequest);
48          }
49      }
50  
51      @Override
52      public void messageSent(NextFilter nextFilter, IoSession session,
53              WriteRequest writeRequest) throws Exception {
54          if (writeRequest instanceof FilteredWriteRequest) {
55              FilteredWriteRequest req = (FilteredWriteRequest) writeRequest;
56              if (req.getParent() == this) {
57                  nextFilter.messageSent(session, req.getParentRequest());
58                  return;
59              }
60          }
61  
62          nextFilter.messageSent(session, writeRequest);
63      }
64  
65      protected abstract Object doFilterWrite(
66              NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws Exception;
67  
68      private class FilteredWriteRequest extends WriteRequestWrapper {
69          private final Object filteredMessage;
70  
71          public FilteredWriteRequest(Object filteredMessage, WriteRequest writeRequest) {
72              super(writeRequest);
73  
74              if (filteredMessage == null) {
75                  throw new NullPointerException("filteredMessage");
76              }
77              this.filteredMessage = filteredMessage;
78          }
79  
80          public WriteRequestFilter getParent() {
81              return WriteRequestFilter.this;
82          }
83  
84          @Override
85          public Object getMessage() {
86              return filteredMessage;
87          }
88      }
89  }