netty初步

netty是java的高性能socket框架，linux下基epoll，这里不对他多牛逼作分析，网上资料很多，这里针对一般socket的业务作个例子

几个基本概念：

　　channel类似于socket句柄的抽象
　　pipeline是每个socket里面的eventHandler的处理响应链

 

每个socket（channel）绑定一个pipeline，，每个pipeline绑定若干个handler，netty里面的handler，专门用来处理和业务有关的东西，handler有upHandler和downHandler，down用来处理发包，up用来处理收包，大概的示例图看这里

注意上面的123的顺序，很重要，在netty里面，处理顺序如图，对于up类的收包处理，最靠近收包层的顺序越靠前；对于down类的包处理，最靠近收包层的顺序越靠后

还有一些encoder和decoder，encoder用来在发包之前进行加密，decoder在收包以后进行解码，然后业务数据跳到事件处理流程。

 

下面具体上代码，版本是netty3.6

MessageClientHandler.java

 1 package com.netty.test.client;

 2 

 3 import java.util.logging.Level;

 4 import java.util.logging.Logger;

 5 

 6 import org.jboss.netty.channel.ChannelHandlerContext;

 7 import org.jboss.netty.channel.ChannelStateEvent;

 8 import org.jboss.netty.channel.ExceptionEvent;

 9 import org.jboss.netty.channel.MessageEvent;

10 import org.jboss.netty.channel.SimpleChannelUpstreamHandler;

11 

12 public class MessageClientHandler extends SimpleChannelUpstreamHandler {

13  

14     private static final Logger logger = Logger.getLogger(

15             MessageClientHandler.class.getName());

16  

17  

18     @Override

19     public void channelConnected(

20             ChannelHandlerContext ctx, ChannelStateEvent e) {

21         String message = "hello kafka0102";

22         e.getChannel().write(message);

23     }

24  

25     @Override

26     public void messageReceived(

27             ChannelHandlerContext ctx, MessageEvent e) {

28         // Send back the received message to the remote peer.

29         System.err.println("client messageReceived send message "+e.getMessage());

30         try {

31             Thread.sleep(1000*3);

32         } catch (Exception ex) {

33             ex.printStackTrace();

34         }

35         e.getChannel().write(e.getMessage());

36     }

37  

38     @Override

39     public void exceptionCaught(

40             ChannelHandlerContext ctx, ExceptionEvent e) {

41         // Close the connection when an exception is raised.

42         logger.log(

43                 Level.WARNING,

44                 "Unexpected exception from downstream.",

45                 e.getCause());

46         e.getChannel().close();

47     }

48 }

 

MessageDecoder.java

 1 package com.netty.test.client;

 2 import org.jboss.netty.buffer.ChannelBuffer;

 3 import org.jboss.netty.channel.Channel;

 4 import org.jboss.netty.channel.ChannelHandlerContext;

 5 import org.jboss.netty.handler.codec.frame.FrameDecoder;

 6 

 7 public class MessageDecoder extends FrameDecoder {

 8  

 9     @Override

10     protected Object decode(

11             ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer) throws Exception {

12         if (buffer.readableBytes() < 4) {

13             return null;//(1)

14         }

15         int dataLength = buffer.getInt(buffer.readerIndex());

16         if (buffer.readableBytes() < dataLength + 4) {

17             return null;//(2)

18         }

19  

20         buffer.skipBytes(4);//(3)

21         byte[] decoded = new byte[dataLength];

22         buffer.readBytes(decoded);

23         String msg = new String(decoded);//(4)

24         return msg;

25     }

26 }

 

MessageEncoder.java

 1 package com.netty.test.client;

 2 import org.jboss.netty.buffer.ChannelBuffer;

 3 import org.jboss.netty.buffer.ChannelBuffers;

 4 import org.jboss.netty.channel.Channel;

 5 import org.jboss.netty.channel.ChannelHandlerContext;

 6 import org.jboss.netty.handler.codec.oneone.OneToOneEncoder;

 7 

 8 public class MessageEncoder extends OneToOneEncoder {

 9  

10     @Override

11     protected Object encode(

12             ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {

13         if (!(msg instanceof String)) {

14             return msg;//(1)

15         }

16  

17         String res = (String)msg;

18         byte[] data = res.getBytes();

19         int dataLength = data.length;

20         ChannelBuffer buf = ChannelBuffers.dynamicBuffer();//(2)

21         buf.writeInt(dataLength);

22         buf.writeBytes(data);

23         return buf;//(3)

24     }

25 }

 

用来测试的TestClientDownHandlerA.java

 1 package com.netty.test.client;

 2 

 3 import org.jboss.netty.channel.ChannelEvent;

 4 import org.jboss.netty.channel.ChannelHandlerContext;

 5 import org.jboss.netty.channel.SimpleChannelDownstreamHandler;

 6 

 7 public class TestClientDownHandlerA extends SimpleChannelDownstreamHandler {

 8      

 9     public void handleDownstream(ChannelHandlerContext ctx, ChannelEvent e)

10             throws Exception {

11         System.err.println("test client Down handlerA ");

12         

13         super.handleDownstream(ctx, e);

14     }

15 }

 

用来测试的TestClientDownHandlerB.java

 1 package com.netty.test.client;

 2 

 3 import org.jboss.netty.channel.ChannelEvent;

 4 import org.jboss.netty.channel.ChannelHandlerContext;

 5 import org.jboss.netty.channel.SimpleChannelDownstreamHandler;

 6 

 7 public class TestClientDownHandlerB extends SimpleChannelDownstreamHandler {

 8      

 9     public void handleDownstream(ChannelHandlerContext ctx, ChannelEvent e)

10             throws Exception {

11         System.err.println("test client Down handlerB ");

12         

13         super.handleDownstream(ctx, e);

14     }

15 }

 

MessageClientPipelineFactory.java

 1 package com.netty.test.client;

 2 

 3 import org.jboss.netty.channel.ChannelPipeline;

 4 import org.jboss.netty.channel.ChannelPipelineFactory;

 5 import org.jboss.netty.channel.Channels;

 6 

 7 import com.netty.test.client.MessageDecoder;

 8 import com.netty.test.client.MessageEncoder;

 9 

10 public class MessageClientPipelineFactory implements ChannelPipelineFactory {

11 

12     public ChannelPipeline getPipeline() throws Exception {

13         ChannelPipeline pipeline = Channels.pipeline();

14         

15         pipeline.addLast("decoder", new MessageDecoder());

16         pipeline.addLast("encoder", new MessageEncoder());

17         pipeline.addLast("handler", new MessageClientHandler());

18 

19         pipeline.addFirst("testClientDownHandlerA", new TestClientDownHandlerA());

20         pipeline.addFirst("testClientDownHandlerB", new TestClientDownHandlerB());

21         

22         return pipeline;

23     }

24 }

 

MessageClient.java

 1 package com.netty.test.client;

 2 

 3 import java.net.InetSocketAddress;

 4 import java.util.concurrent.Executors;

 5 import org.jboss.netty.bootstrap.ClientBootstrap;

 6 import org.jboss.netty.channel.ChannelFuture;

 7 import org.jboss.netty.channel.socket.nio.NioClientSocketChannelFactory;

 8 

 9 public class MessageClient {

10  

11     public static void main(String[] args) throws Exception {

12         // Parse options.

13         String host = "127.0.0.1";

14         int port = 8888;

15         // Configure the client.

16         ClientBootstrap bootstrap = new ClientBootstrap(

17                 new NioClientSocketChannelFactory(

18                         Executors.newCachedThreadPool(),

19                         Executors.newCachedThreadPool()));

20         // Set up the event pipeline factory.

21         bootstrap.setPipelineFactory(new MessageClientPipelineFactory());

22         // Start the connection attempt.

23         ChannelFuture future = bootstrap.connect(new InetSocketAddress(host, port));

24         // Wait until the connection is closed or the connection attempt fails.

25         future.getChannel().getCloseFuture().awaitUninterruptibly();

26         // Shut down thread pools to exit.

27         bootstrap.releaseExternalResources();

28     }

29 }

客户端代码完成

 

 

以下为服务端测试代码

MessageDecoder和Messagencoder照抄，这个都是一样的

MessageServerHandler.java

 1 package com.netty.test.server;

 2 import java.util.logging.Level;

 3 import java.util.logging.Logger;

 4 

 5 import org.jboss.netty.channel.ChannelHandlerContext;

 6 import org.jboss.netty.channel.ExceptionEvent;

 7 import org.jboss.netty.channel.MessageEvent;

 8 import org.jboss.netty.channel.SimpleChannelUpstreamHandler;

 9 

10 public class MessageServerHandler extends SimpleChannelUpstreamHandler {

11  

12     private static final Logger logger = Logger.getLogger(

13             MessageServerHandler.class.getName());

14  

15     @Override

16     public void messageReceived(

17             ChannelHandlerContext ctx, MessageEvent e) {

18         if (!(e.getMessage() instanceof String)) {

19             return;//(1)

20         }

21         String msg = (String) e.getMessage();

22         System.err.println("got msg:"+msg);

23         e.getChannel().write(msg);//(2)

24     }

25  

26     @Override

27     public void exceptionCaught(

28             ChannelHandlerContext ctx, ExceptionEvent e) {

29         logger.log(

30                 Level.WARNING,

31                 "Unexpected exception from downstream.",

32                 e.getCause());

33         e.getChannel().close();

34     }

35 }

 

TestServerUpHandlerA.java

 1 package com.netty.test.server;

 2 

 3 import org.jboss.netty.channel.ChannelHandlerContext;

 4 import org.jboss.netty.channel.ExceptionEvent;

 5 import org.jboss.netty.channel.MessageEvent;

 6 import org.jboss.netty.channel.SimpleChannelUpstreamHandler;

 7 

 8 public class TestServerUpHandlerA extends SimpleChannelUpstreamHandler {

 9      

10     @Override

11     public void messageReceived(

12             ChannelHandlerContext ctx, MessageEvent e) {

13         // Send back the received message to the remote peer.

14         System.err.println("server test upHandlerA get message "+e.getMessage());

15 

16         try {

17             super.messageReceived(ctx, e);

18         } catch (Exception e1) {

19             // TODO Auto-generated catch block

20             e1.printStackTrace();

21         }

22     }

23  

24     @Override

25     public void exceptionCaught(

26             ChannelHandlerContext ctx, ExceptionEvent e) {

27 

28         e.getChannel().close();

29     }

30 }

 

TestServerUpHandlerB.java

 1 package com.netty.test.server;

 2 

 3 import org.jboss.netty.channel.ChannelHandlerContext;

 4 import org.jboss.netty.channel.ExceptionEvent;

 5 import org.jboss.netty.channel.MessageEvent;

 6 import org.jboss.netty.channel.SimpleChannelUpstreamHandler;

 7 

 8 public class TestServerUpHandlerB extends SimpleChannelUpstreamHandler {

 9      

10     @Override

11     public void messageReceived(

12             ChannelHandlerContext ctx, MessageEvent e) {

13         // Send back the received message to the remote peer.

14         System.err.println("server test upHandlerB get message "+e.getMessage());

15 

16         try {

17             super.messageReceived(ctx, e);

18         } catch (Exception e1) {

19             // TODO Auto-generated catch block

20             e1.printStackTrace();

21         }

22     }

23  

24     @Override

25     public void exceptionCaught(

26             ChannelHandlerContext ctx, ExceptionEvent e) {

27 

28         e.getChannel().close();

29     }

30 }

 

MessageServerPipelineFactory.java

 1 package com.netty.test.server;

 2 

 3 import org.jboss.netty.channel.ChannelPipeline;

 4 import org.jboss.netty.channel.ChannelPipelineFactory;

 5 import org.jboss.netty.channel.Channels;

 6 

 7 public class MessageServerPipelineFactory implements

 8         ChannelPipelineFactory {

 9  

10     public ChannelPipeline getPipeline() throws Exception {

11         ChannelPipeline pipeline = Channels.pipeline();

12  

13         pipeline.addLast("decoder", new MessageDecoder());

14         pipeline.addLast("encoder", new MessageEncoder());

15         pipeline.addLast("handler", new MessageServerHandler());

16         

17 //        pipeline.addFirst("testServerUpHandlerA", new TestServerUpHandlerA());

18 //        pipeline.addFirst("testServerUpHandlerB", new TestServerUpHandlerB());

19         

20         return pipeline;

21     }

22 }

 

MessageServer.java

 1 package com.netty.test.server;

 2 

 3 import java.net.InetSocketAddress;

 4 import java.util.concurrent.Executors;

 5 import org.jboss.netty.bootstrap.ServerBootstrap;

 6 import org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory;

 7 

 8 public class MessageServer {

 9  

10     public static void main(String[] args) throws Exception {

11         // Configure the server.

12         ServerBootstrap bootstrap = new ServerBootstrap(

13                 new NioServerSocketChannelFactory(

14                         Executors.newCachedThreadPool(),

15                         Executors.newCachedThreadPool()));

16  

17         // Set up the default event pipeline.

18         bootstrap.setPipelineFactory(new MessageServerPipelineFactory());

19  

20         // Bind and start to accept incoming connections.

21         bootstrap.bind(new InetSocketAddress(8888));

22     }

23 }

通过测试，可以发现handler的处理顺序，和图上面的是一致的；还有可以参考下encoder和decoder的写法，改改，直接用于项目。