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

package com.netty.test.client;

import java.util.logging.Level;
import java.util.logging.Logger;

import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ChannelStateEvent;
import org.jboss.netty.channel.ExceptionEvent;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelUpstreamHandler;

public class MessageClientHandler extends SimpleChannelUpstreamHandler {
 
    private static final Logger logger = Logger.getLogger(
            MessageClientHandler.class.getName());
 
 
    @Override
    public void channelConnected(
            ChannelHandlerContext ctx, ChannelStateEvent e) {
        String message = "hello kafka0102";
        e.getChannel().write(message);
    }
 
    @Override
    public void messageReceived(
            ChannelHandlerContext ctx, MessageEvent e) {
        // Send back the received message to the remote peer.
        System.err.println("client messageReceived send message "+e.getMessage());
        try {
            Thread.sleep(1000*3);
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        e.getChannel().write(e.getMessage());
    }
 
    @Override
    public void exceptionCaught(
            ChannelHandlerContext ctx, ExceptionEvent e) {
        // Close the connection when an exception is raised.
        logger.log(
                Level.WARNING,
                "Unexpected exception from downstream.",
                e.getCause());
        e.getChannel().close();
    }
}

MessageDecoder.java

package com.netty.test.client;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.frame.FrameDecoder;

public class MessageDecoder extends FrameDecoder {
 
    @Override
    protected Object decode(
            ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer) throws Exception {
        if (buffer.readableBytes() < 4) {
            return null;//(1)
        }
        int dataLength = buffer.getInt(buffer.readerIndex());
        if (buffer.readableBytes() < dataLength + 4) {
            return null;//(2)
        }
 
        buffer.skipBytes(4);//(3)
        byte[] decoded = new byte[dataLength];
        buffer.readBytes(decoded);
        String msg = new String(decoded);//(4)
        return msg;
    }
}

MessageEncoder.java

package com.netty.test.client;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.oneone.OneToOneEncoder;

public class MessageEncoder extends OneToOneEncoder {
 
    @Override
    protected Object encode(
            ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
        if (!(msg instanceof String)) {
            return msg;//(1)
        }
 
        String res = (String)msg;
        byte[] data = res.getBytes();
        int dataLength = data.length;
        ChannelBuffer buf = ChannelBuffers.dynamicBuffer();//(2)
        buf.writeInt(dataLength);
        buf.writeBytes(data);
        return buf;//(3)
    }
}

用来测试的TestClientDownHandlerA.java

package com.netty.test.client;

import org.jboss.netty.channel.ChannelEvent;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.SimpleChannelDownstreamHandler;

public class TestClientDownHandlerA extends SimpleChannelDownstreamHandler {
     
    public void handleDownstream(ChannelHandlerContext ctx, ChannelEvent e)
            throws Exception {
        System.err.println("test client Down handlerA ");
        
        super.handleDownstream(ctx, e);
    }
}

用来测试的TestClientDownHandlerB.java

package com.netty.test.client;

import org.jboss.netty.channel.ChannelEvent;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.SimpleChannelDownstreamHandler;

public class TestClientDownHandlerB extends SimpleChannelDownstreamHandler {
     
    public void handleDownstream(ChannelHandlerContext ctx, ChannelEvent e)
            throws Exception {
        System.err.println("test client Down handlerB ");
        
        super.handleDownstream(ctx, e);
    }
}

MessageClientPipelineFactory.java

package com.netty.test.client;

import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.channel.Channels;

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

public class MessageClientPipelineFactory implements ChannelPipelineFactory {

    public ChannelPipeline getPipeline() throws Exception {
        ChannelPipeline pipeline = Channels.pipeline();
        
        pipeline.addLast("decoder", new MessageDecoder());
        pipeline.addLast("encoder", new MessageEncoder());
        pipeline.addLast("handler", new MessageClientHandler());

        pipeline.addFirst("testClientDownHandlerA", new TestClientDownHandlerA());
        pipeline.addFirst("testClientDownHandlerB", new TestClientDownHandlerB());
        
        return pipeline;
    }
}

MessageClient.java

package com.netty.test.client;

import java.net.InetSocketAddress;
import java.util.concurrent.Executors;
import org.jboss.netty.bootstrap.ClientBootstrap;
import org.jboss.netty.channel.ChannelFuture;
import org.jboss.netty.channel.socket.nio.NioClientSocketChannelFactory;

public class MessageClient {
 
    public static void main(String[] args) throws Exception {
        // Parse options.
        String host = "127.0.0.1";
        int port = 8888;
        // Configure the client.
        ClientBootstrap bootstrap = new ClientBootstrap(
                new NioClientSocketChannelFactory(
                        Executors.newCachedThreadPool(),
                        Executors.newCachedThreadPool()));
        // Set up the event pipeline factory.
        bootstrap.setPipelineFactory(new MessageClientPipelineFactory());
        // Start the connection attempt.
        ChannelFuture future = bootstrap.connect(new InetSocketAddress(host, port));
        // Wait until the connection is closed or the connection attempt fails.
        future.getChannel().getCloseFuture().awaitUninterruptibly();
        // Shut down thread pools to exit.
        bootstrap.releaseExternalResources();
    }
}

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

package com.netty.test.server;
import java.util.logging.Level;
import java.util.logging.Logger;

import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ExceptionEvent;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelUpstreamHandler;

public class MessageServerHandler extends SimpleChannelUpstreamHandler {
 
    private static final Logger logger = Logger.getLogger(
            MessageServerHandler.class.getName());
 
    @Override
    public void messageReceived(
            ChannelHandlerContext ctx, MessageEvent e) {
        if (!(e.getMessage() instanceof String)) {
            return;//(1)
        }
        String msg = (String) e.getMessage();
        System.err.println("got msg:"+msg);
        e.getChannel().write(msg);//(2)
    }
 
    @Override
    public void exceptionCaught(
            ChannelHandlerContext ctx, ExceptionEvent e) {
        logger.log(
                Level.WARNING,
                "Unexpected exception from downstream.",
                e.getCause());
        e.getChannel().close();
    }
}

TestServerUpHandlerA.java

package com.netty.test.server;

import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ExceptionEvent;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelUpstreamHandler;

public class TestServerUpHandlerA extends SimpleChannelUpstreamHandler {
     
    @Override
    public void messageReceived(
            ChannelHandlerContext ctx, MessageEvent e) {
        // Send back the received message to the remote peer.
        System.err.println("server test upHandlerA get message "+e.getMessage());

        try {
            super.messageReceived(ctx, e);
        } catch (Exception e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
    }
 
    @Override
    public void exceptionCaught(
            ChannelHandlerContext ctx, ExceptionEvent e) {

        e.getChannel().close();
    }
}

TestServerUpHandlerB.java

package com.netty.test.server;

import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ExceptionEvent;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelUpstreamHandler;

public class TestServerUpHandlerB extends SimpleChannelUpstreamHandler {
     
    @Override
    public void messageReceived(
            ChannelHandlerContext ctx, MessageEvent e) {
        // Send back the received message to the remote peer.
        System.err.println("server test upHandlerB get message "+e.getMessage());

        try {
            super.messageReceived(ctx, e);
        } catch (Exception e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
    }
 
    @Override
    public void exceptionCaught(
            ChannelHandlerContext ctx, ExceptionEvent e) {

        e.getChannel().close();
    }
}

MessageServerPipelineFactory.java

package com.netty.test.server;

import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.channel.Channels;

public class MessageServerPipelineFactory implements
        ChannelPipelineFactory {
 
    public ChannelPipeline getPipeline() throws Exception {
        ChannelPipeline pipeline = Channels.pipeline();
 
        pipeline.addLast("decoder", new MessageDecoder());
        pipeline.addLast("encoder", new MessageEncoder());
        pipeline.addLast("handler", new MessageServerHandler());
        
//        pipeline.addFirst("testServerUpHandlerA", new TestServerUpHandlerA());
//        pipeline.addFirst("testServerUpHandlerB", new TestServerUpHandlerB());
        
        return pipeline;
    }
}

MessageServer.java

package com.netty.test.server;

import java.net.InetSocketAddress;
import java.util.concurrent.Executors;
import org.jboss.netty.bootstrap.ServerBootstrap;
import org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory;

public class MessageServer {
 
    public static void main(String[] args) throws Exception {
        // Configure the server.
        ServerBootstrap bootstrap = new ServerBootstrap(
                new NioServerSocketChannelFactory(
                        Executors.newCachedThreadPool(),
                        Executors.newCachedThreadPool()));
 
        // Set up the default event pipeline.
        bootstrap.setPipelineFactory(new MessageServerPipelineFactory());
 
        // Bind and start to accept incoming connections.
        bootstrap.bind(new InetSocketAddress(8888));
    }
}

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。