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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.example.reverser;
21  
22  import org.apache.mina.core.service.IoHandler;
23  import org.apache.mina.core.service.IoHandlerAdapter;
24  import org.apache.mina.core.session.IoSession;
25  
26  /**
27   * {@link IoHandler} implementation of reverser server protocol.
28   *
29   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
30   */
31  public class ReverseProtocolHandler extends IoHandlerAdapter {
32      @Override
33      public void exceptionCaught(IoSession session, Throwable cause) {
34          // Close connection when unexpected exception is caught.
35          session.close(true);
36      }
37  
38      @Override
39      public void messageReceived(IoSession session, Object message) {
40          // Reverse reveiced string
41          String str = message.toString();
42          StringBuilder buf = new StringBuilder(str.length());
43          for (int i = str.length() - 1; i >= 0; i--) {
44              buf.append(str.charAt(i));
45          }
46  
47          // and write it back.
48          session.write(buf.toString());
49      }
50  }