Java NIO Framework Netty Tutorial (eight) object objects passing

Say so much nonsense, only to mention the transmission of objects, do not know whether you are impatient. It is not realistic to pass the message inside a system without object passing. Let's say, how to pass the object.

If you have seen the previous introduction, if you are good at focusing on the essence, diligent thinking. You should also think, as we have said, that Netty's message delivery is flow-based, passing through Channelbuffer, then naturally, object also needs to be converted to Channelbuffer to pass. Fortunately, Netty itself has written such a conversion tool for us. Objectencoder and Objectdecoder.

How does the tool work? Once again the so-called essence, as we have said before, Netty gives us the space to deal with our business is on the flexible definable handler, that is to say, if we do this transformation work, then we should also do in the handler. And Netty, provided to our objectencoder and decoder is precisely a group of handler. Then, modify the startup code for the server and client:

View Sourceprint? 01. // 设置一个处理客户端消息和各种消息事件的类(Handler) 02. bootstrap.setPipelineFactory( new  ChannelPipelineFactory() { 03. @Override 04. public  ChannelPipeline getPipeline()  throws  Exception { 05. return  Channels.pipeline( 06. new  ObjectDecoder(ClassResolvers.cacheDisabled( this 07. .getClass().getClassLoader())), 08. new  ObjectServerHandler()); 09. } 10. }); // 设置一个处理服务端消息和各种消息事件的类(Handler) 11. bootstrap.setPipelineFactory( new  ChannelPipelineFactory() { 12. @Override 13. public  ChannelPipeline getPipeline()  throws  Exception { 14. return  Channels.pipeline( new  ObjectEncoder(), 15. new  ObjectClientHandler()); 16. } 17. });

To pass an object, it is natural to have a passing model, a simple pojo, and of course, implementing a serialized interface is a must.

View Sourceprint? 01. /** 02. * @author lihzh 03. * @alia OneCoder 04. * @blog http://www.it165.net 05. */ 06. public  class  Command  implements  Serializable { 07.  08. private  static  final  long  serialVersionUID = 7590999461767050471L; 09.  10. private  String actionName; 11.  12. public  String getActionName() { 13. return  actionName; 14. } 15.  16. public  void  setActionName(String actionName) { 17. this .actionName = actionName; 18. } 19. }

Service side and client, our custom handler implementation is as follows:

View Sourceprint? 01. /** 02. * 对象传递服务端代码 03. * 04. * @author lihzh 05. * @alia OneCoder 06. * @blog http://www.it165.net 07. */ 08. public  class  ObjectServerHandler  extends  SimpleChannelHandler { 09.  10. /** 11. * 当接受到消息的时候触发www.it165.net 12. */ 13. @Override 14. public  void  messageReceived(ChannelHandlerContext ctx, MessageEvent e) 15. throws  Exception { 16. Command command = (Command) e.getMessage(); 17. // 打印看看是不是我们刚才传过来的那个 18. System.out.println(command.getActionName()); 19. } 20. } /** 21. * 对象传递，客户端代码 22. * 23. * @author lihzh 24. * @alia OneCoder 25. * @blog http://www.it165.net 26. */ 27. public  class  ObjectClientHandler  extends  SimpleChannelHandler { 28.  29. /** 30. * 当绑定到服务端的时候触发，给服务端发消息。 31. * 32. * @author lihzh 33. * @alia OneCoder 34. */ 35. @Override 36. public  void  channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e) { 37. // 向服务端发送Object信息 38. sendObject(e.getChannel()); 39. } 40.  41. /** 42. * 发送Object 43. * 44. * @param channel 45. * @author lihzh 46. * @alia OneCoder 47. */ 48. private  void  sendObject(Channel channel) { 49. Command command =  new  Command(); 50. command.setActionName( "Hello action." ); 51. channel.write(command); 52. } 53.  54. }

After startup, the service side normally prints the result: Hello action.

Simply comb your thoughts:

1. Pass through the Netty, all need to flow based, in the form of Channelbuffer. So, Object---Channelbuffer.
2. Netty provides a conversion tool that requires us to configure to handler.
3. Sample from the client-side server, one-way message, so the client configured the encoding, the service-side decoding. If you are sending and receiving two-way, you need to configure encoder and decoder.

It is important to note that the handler registered to the server are sequential, if you reverse the registration order:

View Sourceprint? 01. bootstrap.setPipelineFactory( new  ChannelPipelineFactory() { 02. @Override 03. public  ChannelPipeline getPipeline()  throws  Exception { 04. return  Channels.pipeline( new  ObjectServerHandler(), 05. new  ObjectDecoder(ClassResolvers.cacheDisabled( this 06. .getClass().getClassLoader())) 07. ); 08. } 09. });

As a result, we will first enter our own business and then decode it. This is not natural, will be strong turn failure. At this point, you should pass the object with Netty.

Java NIO Framework Netty Tutorial (eight) object objects passing