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1   /*** 
2    * 
3    * Copyright 2004 Protique Ltd
4    * 
5    * Licensed under the Apache License, Version 2.0 (the "License"); 
6    * you may not use this file except in compliance with the License. 
7    * You may obtain a copy of the License at 
8    * 
9    * http://www.apache.org/licenses/LICENSE-2.0
10   * 
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS, 
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
14   * See the License for the specific language governing permissions and 
15   * limitations under the License. 
16   * 
17   **/
18  package org.codehaus.activemq.message;
19  
20  import java.io.ByteArrayOutputStream;
21  import java.io.DataOutput;
22  import java.io.DataOutputStream;
23  import java.io.IOException;
24  import java.io.ObjectOutputStream;
25  
26  /***
27   * Allows instances implementing Packet interface to be serailized/deserailized
28   */
29  public abstract class AbstractPacketWriter implements PacketWriter {
30      /***
31       * simple helper method to ensure null strings are catered for
32       *
33       * @param str
34       * @param dataOut
35       * @throws IOException
36       */
37      protected void writeUTF(String str, DataOutput dataOut) throws IOException {
38          if (str == null) {
39              str = "";
40          }
41          dataOut.writeUTF(str);
42      }
43  
44      /***
45       * @param packet
46       * @return true if this PacketWriter can write this type of Packet
47       */
48      public boolean canWrite(Packet packet) {
49          return packet.getPacketType() == this.getPacketType();
50      }
51  
52      /***
53       * Simple (but inefficent) utility method to write an object on to a stream
54       *
55       * @param object
56       * @param dataOut
57       * @throws IOException
58       */
59      protected void writeObject(Object object, DataOutput dataOut) throws IOException {
60          if (object != null) {
61              ByteArrayOutputStream bytesOut = new ByteArrayOutputStream();
62              ObjectOutputStream objOut = new ObjectOutputStream(bytesOut);
63              objOut.writeObject(object);
64              objOut.flush();
65              byte[] data = bytesOut.toByteArray();
66              dataOut.writeInt(data.length);
67              dataOut.write(data);
68          }
69          else {
70              dataOut.writeInt(0);
71          }
72      }
73  
74      /***
75       * Serializes a Packet int a byte array
76       *
77       * @param packet
78       * @return the byte[]
79       * @throws IOException
80       */
81      public byte[] writePacketToByteArray(Packet packet) throws IOException {
82          ByteArrayOutputStream bytesOut = new ByteArrayOutputStream();
83          DataOutputStream dataOut = new DataOutputStream(bytesOut);
84          writePacket(packet, dataOut);
85          dataOut.flush();
86          return bytesOut.toByteArray();
87      }
88  
89      /***
90       * Write a Packet instance to data output stream
91       *
92       * @param packet  the instance to be seralized
93       * @param dataOut the output stream
94       * @throws IOException thrown if an error occurs
95       */
96      public void writePacket(Packet packet, DataOutput dataOut) throws IOException {
97          writeUTF(packet.getId(), dataOut);
98          dataOut.writeBoolean(packet.isReceiptRequired());
99      }
100 }