查看本类的 API文档回源码主页即时通讯网 - 即时通讯开发者社区!
1   /*
2    * Copyright 2012 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package org.jboss.netty.handler.codec.marshalling;
17  
18  import org.jboss.marshalling.Marshaller;
19  import org.jboss.netty.buffer.ChannelBuffer;
20  import org.jboss.netty.channel.Channel;
21  import org.jboss.netty.channel.ChannelHandler.Sharable;
22  import org.jboss.netty.channel.ChannelHandlerContext;
23  import org.jboss.netty.handler.codec.oneone.OneToOneEncoder;
24  
25  /**
26   * {@link OneToOneEncoder} implementation which uses JBoss Marshalling to marshal
27   * an Object. Be aware that this {@link OneToOneEncoder} is not compatible with
28   * an other client that just use JBoss Marshalling as it includes the size of every
29   * {@link Object} that gets serialized in front of the {@link Object} itself.
30   *
31   * Use this with {@link MarshallingDecoder}
32   *
33   * See <a href="http://www.jboss.org/jbossmarshalling">JBoss Marshalling website</a>
34   * for more informations
35   *
36   */
37  @Sharable
38  public class MarshallingEncoder extends OneToOneEncoder {
39      private static final byte[] LENGTH_PLACEHOLDER = new byte[4];
40      private final MarshallerProvider provider;
41  
42      private final int estimatedLength;
43  
44      /**
45       * Creates a new encoder with the estimated length of 512 bytes.
46       *
47       * @param provider the {@link MarshallerProvider} to use
48       */
49      public MarshallingEncoder(MarshallerProvider provider) {
50          this(provider, 512);
51      }
52  
53      /**
54       * Creates a new encoder.
55       *
56       * @param provider
57       *        the {@link MarshallerProvider} to use
58       * @param estimatedLength
59       *        the estimated byte length of the serialized form of an object.
60       *        If the length of the serialized form exceeds this value, the
61       *        internal buffer will be expanded automatically at the cost of
62       *        memory bandwidth.  If this value is too big, it will also waste
63       *        memory bandwidth.  To avoid unnecessary memory copy or allocation
64       *        cost, please specify the properly estimated value.
65       */
66      public MarshallingEncoder(MarshallerProvider provider, int estimatedLength) {
67          if (estimatedLength < 0) {
68              throw new IllegalArgumentException(
69                      "estimatedLength: " + estimatedLength);
70          }
71          this.estimatedLength = estimatedLength;
72          this.provider = provider;
73      }
74  
75      @Override
76      protected Object encode(ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
77          Marshaller marshaller = provider.getMarshaller(ctx);
78          ChannelBufferByteOutput output = new ChannelBufferByteOutput(
79                  ctx.getChannel().getConfig().getBufferFactory(), estimatedLength);
80          output.getBuffer().writeBytes(LENGTH_PLACEHOLDER);
81          marshaller.start(output);
82          marshaller.writeObject(msg);
83          marshaller.finish();
84          marshaller.close();
85  
86          ChannelBuffer encoded = output.getBuffer();
87          encoded.setInt(0, encoded.writerIndex() - 4);
88  
89          return encoded;
90      }
91  
92  }