Java NIO Framework Netty Tutorial (ix) Object object encoding/decoding

See the topic, some students may think, last said the object passed it? Yes, just in the Java NIO Framework Netty Tutorial (eight) The object object is passed, we just show how to use the Netty provided by the codec/Decode tool to complete the serialization of objects. This is to tell you netty specifically how to do, perhaps some students want to complete the serialization of their own? Moreover, the serialization of objects is available everywhere:)

First look at how to encode.

View Sourceprint? 01. @Override 02. protected  Object encode(ChannelHandlerContext ctx, Channel channel, Object msg)  throws  Exception { 03. ChannelBufferOutputStream bout = 04. new  ChannelBufferOutputStream(dynamicBuffer( 05. estimatedLength, ctx.getChannel().getConfig().getBufferFactory())); 06. bout.write(LENGTH_PLACEHOLDER); 07. ObjectOutputStream oout =  new  CompactObjectOutputStream(bout); 08. oout.writeObject(msg); 09. oout.flush(); 10. oout.close(); 11.  12. ChannelBuffer encoded = bout.buffer(); 13. encoded.setInt( 0 , encoded.writerIndex() -  4 ); 14. return  encoded; 15. }

In fact, you should have thought of, in Java in the serialization of the object is naturally not objectoutputstream. Netty This is just another layer of packaging that adds a 4-byte flag to the beginning of the stream. Therefore, Netty declares that the encoding and decoding classes must be used in a complementary, incompatible with the simple objectintputstream.

* An encoder which serializes a Java object into a {@link channelbuffer}.
* <p>
* Please note that the serialized form this encoder produces are not
* Compatible with the standard {@link ObjectInputStream}. Please use
* {@link Objectdecoder} or {@link Objectdecoderinputstream} to ensure the
* Interoperability with this encoder.

Decoding nature is to parse out the extra 4 bits first and then parse through ObjectInputStream.

The details about the serialization of Java objects are beyond the scope of the text discussion, but I wonder if you're interested in trying to write one yourself? So-called, more hands-on.

View Sourceprint? 01. /** 02. * Object编码类 03. * 04. * @author lihzh 05. * @alia OneCoder 06. * @blog http://www.it165.net 07. */ 08. public  class  MyObjEncoder  implements  ChannelDownstreamHandler { 09.  10. @Override 11. public  void  handleDownstream(ChannelHandlerContext ctx, ChannelEvent e) 12. throws  Exception { 13. // 处理收发信息的情形 14. if  (e  instanceof  MessageEvent) { 15. MessageEvent mEvent = (MessageEvent) e; 16. Object obj = mEvent.getMessage(); 17. if  (!(obj  instanceof  Command)) { 18. ctx.sendDownstream(e); 19. return ; 20. } 21. ByteArrayOutputStream out =  new  ByteArrayOutputStream(); 22. ObjectOutputStream oos =  new  ObjectOutputStream(out); 23. oos.writeObject(obj); 24. oos.flush(); 25. oos.close(); 26. ChannelBuffer buffer = ChannelBuffers.dynamicBuffer(); 27. buffer.writeBytes(out.toByteArray()); 28. e.getChannel().write(buffer); 29. }  else  { 30. // 其他事件，自动流转。比如，bind，connected 31. ctx.sendDownstream(e); 32. } 33. } 34. } 35. /** 36. * Object解码类 37. * 38. * @author lihzh 39. * @alia OneCoder 40. * @blog http://www.it165.net 41. */ 42. public  class  MyObjDecoder  implements  ChannelUpstreamHandler { 43.  44. @Override 45. public  void  handleUpstream(ChannelHandlerContext ctx, ChannelEvent e) 46. throws  Exception { 47. if  (e  instanceof  MessageEvent) { 48. MessageEvent mEvent = (MessageEvent) e; 49. if  (!(mEvent.getMessage()  instanceof  ChannelBuffer)) { 50. ctx.sendUpstream(mEvent); 51. return ; 52. } 53. ChannelBuffer buffer = (ChannelBuffer) mEvent.getMessage(); 54. ByteArrayInputStream input =  new  ByteArrayInputStream(buffer.array()); 55. ObjectInputStream ois =  new  ObjectInputStream(input); 56. Object obj = ois.readObject(); 57. Channels.fireMessageReceived(e.getChannel(), obj); 58. } 59. } 60. }

How, is it easy to use? The so-called imitation, to apply.

However, to remind you that this implementation has a lot of hard-coded things, do not imitate, just to show the object, codec processing and application in Netty.

Java NIO Framework Netty Tutorial (ix) Object object encoding/decoding