Netty 3.x 简例

Netty是一个异步的、事件驱动的网络应用框架，可以用来快速开发高性的客户端、服务端程序。示例使用Netty 3.10.5

首先是Server部分的代码：

Server端主程序：

package com.sean.server;

import java.net.InetSocketAddress;
import java.util.concurrent.Executors;

import org.jboss.netty.bootstrap.ServerBootstrap;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelFactory;
import org.jboss.netty.channel.group.ChannelGroup;
import org.jboss.netty.channel.group.ChannelGroupFuture;
import org.jboss.netty.channel.group.DefaultChannelGroup;
import org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory;

public class Server {
	private ChannelFactory factory;
	
	public static ChannelGroup channelGroup = new DefaultChannelGroup();
	
	public void start(){
		// NioServerSocketChannelFactory用于创建基于NIO的服务端
		// ServerSocketChannel。本身包含2种线程，boss线程和worker线程。
		// 每个ServerSocketChannel会都会拥有自己的boss线程，
		// 当一个连接被服务端接受（accepted），
		// boss线程就会将接收到的Channel传递给一个worker线程处理，
		// 而worker线程以非阻塞的方式为一个或多个Channel提供非阻塞的读写
		factory = new NioServerSocketChannelFactory(
				Executors.newCachedThreadPool(),	// boss线程池
				Executors.newCachedThreadPool(),	// worker线程池
				8);	// worker线程数
		
		// ServerBootstrap用于帮助服务器启动
		ServerBootstrap bootstrap = new ServerBootstrap(factory);
		
		// 没有child.前缀，则该选项是为ServerSocketChannel设置
		bootstrap.setOption("reuseAddress", true);
		// 有child.前缀，则该选项是为Channel设置
//		bootstrap.setOption("child.tcpNoDelay", true);
//		bootstrap.setOption("child.keepAlive", true);
	
		// 对每一个连接（channel），server都会调用
		// ChannelPipelineFactory为该连接创建一个ChannelPipeline
		ServerChannelPiplineFactory channelPiplineFactory =
				new ServerChannelPiplineFactory();
		bootstrap.setPipelineFactory(channelPiplineFactory);
		
		// 这里绑定服务端监听的IP和端口
		Channel channel = bootstrap.bind(new InetSocketAddress("127.0.0.1", 8000));
		Server.channelGroup.add(channel);
		
		System.out.println("Server is started...");
	}
	
	public void stop(){
		// ChannelGroup为其管理的Channels提供一系列的批量操作
		// 关闭的Channel会自动从ChannelGroup中移除
		ChannelGroupFuture channelGroupFuture = Server.channelGroup.close();
		channelGroupFuture.awaitUninterruptibly();
		factory.releaseExternalResources();
		System.out.println("Server is stopped.");
	}

	public static void main(String[] args) throws Exception {
		Server server = new Server();
		server.start();
		Thread.sleep(30*1000);
		server.stop();
	}
}

PipelineFactory：

package com.sean.server;

import java.util.concurrent.Executor;

import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.channel.Channels;
import org.jboss.netty.handler.execution.OrderedMemoryAwareThreadPoolExecutor;

import com.sean.server.handler.ServerExecutionHandler;
import com.sean.server.handler.ServerLogicHandler;
import com.sean.server.handler.ServerReadDecoder;
import com.sean.server.handler.ServerWriteEncoder;

public class ServerChannelPiplineFactory implements ChannelPipelineFactory {

	@Override
	public ChannelPipeline getPipeline() throws Exception {
		ServerReadDecoder serverReadDecoder = new ServerReadDecoder();
		ServerWriteEncoder serverWriteEncoder = new ServerWriteEncoder();
		Executor executor = 
				new OrderedMemoryAwareThreadPoolExecutor(4, 200, 200);
		ServerExecutionHandler serverExecutionHandler = 
				new ServerExecutionHandler(executor);
		ServerLogicHandler serverLogicHandler = new ServerLogicHandler();
		
		// ChannelPipeline的源码中的javadoc介绍的非常详细，很有必要看一下
		// ChannelPipeline是一个处理ChannelEvent的handler链
		// 如果为读操作，ChannelEvent事件会从前到后依次被
		// Upstream的handler处理
		// serverReadDecoder -> serverLogicHandler
		// 如果为写操作，ChannelEvent事件会从后至前依次被
		// Downstream的handler处理
		// serverLogicHandler -> serverWriteEncoder
		ChannelPipeline channelPipeline = Channels.pipeline();
		channelPipeline.addLast("1", serverReadDecoder);
		channelPipeline.addLast("2", serverWriteEncoder);
		channelPipeline.addLast("3", serverExecutionHandler);
		channelPipeline.addLast("4", serverLogicHandler);
		
		System.out.println(channelPipeline.hashCode());
		return channelPipeline;
	}

}

各个Handler：

package com.sean.server.handler;

import java.util.concurrent.Executor;

import org.jboss.netty.handler.execution.ExecutionHandler;

// 提供一个线程池
public class ServerExecutionHandler extends ExecutionHandler{

	public ServerExecutionHandler(Executor executor) {
		super(executor);
	}
}

package com.sean.server.handler;

import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelFuture;
import org.jboss.netty.channel.ChannelFutureListener;
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.SimpleChannelHandler;

import com.sean.server.Server;

// SimpleChannelHandler提供了很多基本的handler方法用来重写
// 通常情况下足够使用了
public class ServerLogicHandler extends SimpleChannelHandler {
	@Override
	public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e)
			throws Exception {
		System.out.println("######channelConnected");
		// channel group is thread safe
		Server.channelGroup.add(e.getChannel());
		System.out.println(e.getChannel().toString());
	}

	@Override
    public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) {
		System.out.println("######messageReceived");
		
		// 经过了ServerReadDecoder的处理，这里可以直接得到String类型的message
		String msg = (String)e.getMessage();
		System.out.println("The message sent by client is : " + msg);
		
		Channel ch = e.getChannel();
		String str = "Hi, Client.";
		// 由于IO操作是异步的，当方法返回时并不能保证IO操作一定完成了
		// 因此返回一个ChannelFuture对象实例
		// 该实例中保存了IO操作的状态信息
		ChannelFuture cf = ch.write(str);
		// 为ChannelFuture对象实例添加监听，如果数据发送完毕则关闭连接
		cf.addListener(new ChannelFutureListener(){
			@Override
			public void operationComplete(ChannelFuture future)
					throws Exception {
				Channel ch = future.getChannel();
				ch.close();
			}
		});
		
		System.out.println("The message has sent to client.");
	}
 
	@Override
    public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) {
		e.getCause().printStackTrace();
	    Channel ch = e.getChannel();
        ch.close();
	}
}

package com.sean.server.handler;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.string.StringDecoder;
import org.jboss.netty.util.CharsetUtil;

// 解决接收流数据时，数据出现碎片化的问题
public class ServerReadDecoder extends StringDecoder{

	@Override
	protected Object decode(ChannelHandlerContext ctx, Channel channel,
			Object msg) throws Exception {
		System.out.println("######ServerReadDecoder");
		
		// 从msg中取出的数据类型是ChannelBuffer的
		byte[] buffer = ((ChannelBuffer)msg).array();
		byte last = buffer[buffer.length - 1];
		// 46 is '.'
		if(last == 46)
			// 并将ChannelBuffer转为String
			return new String(buffer, CharsetUtil.UTF_8);
		return null;
	}
}

package com.sean.server.handler;

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.string.StringEncoder;
import org.jboss.netty.util.CharsetUtil;

public class ServerWriteEncoder extends StringEncoder{

	@Override
	protected Object encode(ChannelHandlerContext ctx, Channel channel,
			Object msg) throws Exception {
		System.out.println("######ServerWriteEncoder");
		
		String str = (String)msg;
		// 通过ChannelBuffers工具，为指定编码的指定字符串分配缓存空间
		// 并将String转为ChannelBuffer
		ChannelBuffer channelBuffer = 
				ChannelBuffers.copiedBuffer(str, CharsetUtil.UTF_8);
		return channelBuffer;
	}
}

然后是Client部分的代码：

Client端主程序：

package com.sean.client;

import java.net.InetSocketAddress;
import java.util.concurrent.Executors;

import org.jboss.netty.bootstrap.ClientBootstrap;
import org.jboss.netty.channel.ChannelFactory;
import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.channel.Channels;
import org.jboss.netty.channel.socket.nio.NioClientSocketChannelFactory;

import com.sean.client.handler.ClientLogicHandler;
import com.sean.client.handler.ClientReadDecoder;
import com.sean.client.handler.ClientWriteEncoder;

public class Client {
	public static void main(String[] args){
		// 同服务端相同，只是这里使用的是NioClientSocketChannelFactory
		final ChannelFactory factory = new NioClientSocketChannelFactory(
				Executors.newCachedThreadPool(),	
				Executors.newCachedThreadPool(),	
				8);	
		
		// ClientBootstrap用于帮助客户端启动
		ClientBootstrap bootstrap = new ClientBootstrap(factory);
		// 由于客户端不包含ServerSocketChannel，所以参数名不能带有child.前缀
		bootstrap.setOption("tcpNoDelay", true);
//		bootstrap.setOption("keepAlive", true);
	
		bootstrap.setPipelineFactory(new ChannelPipelineFactory(){
			@Override
			public ChannelPipeline getPipeline() throws Exception {
				ChannelPipeline channelPipeline =
						Channels.pipeline(new ClientReadDecoder(), 
						new ClientWriteEncoder(), new ClientLogicHandler());
				
				System.out.println(channelPipeline.hashCode());
				return channelPipeline;
			}
		});
		
		// 这里连接服务端绑定的IP和端口
		bootstrap.connect(new InetSocketAddress("127.0.0.1", 8000));
		System.out.println("Client is started...");
	}
}

各个Handler：

package com.sean.client.handler;

import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelFuture;
import org.jboss.netty.channel.ChannelFutureListener;
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.SimpleChannelHandler;
import org.jboss.netty.channel.WriteCompletionEvent;

public class ClientLogicHandler extends SimpleChannelHandler {
	
	@Override
	public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e)
			throws Exception {
		System.out.println("######channelConnected");
		
		Channel ch = e.getChannel();
		String msg = "Hi, Server.";
		ch.write(msg);
	}

	@Override
	public void writeComplete(ChannelHandlerContext ctx, WriteCompletionEvent e)
			throws Exception {
		System.out.println("######writeComplete");
	}

	@Override
    public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) {
		System.out.println("######messageReceived");
		
		String msg = (String)e.getMessage();
		System.out.println("The message gotten from server is : " + msg);
		
		ChannelFuture channelFuture = e.getChannel().close();
		channelFuture.addListener(ChannelFutureListener.CLOSE);
	}

	@Override
    public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) {
		e.getCause().printStackTrace();
	    Channel ch = e.getChannel();
        ch.close();
	}
}

package com.sean.client.handler;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.string.StringDecoder;
import org.jboss.netty.util.CharsetUtil;

public class ClientReadDecoder extends StringDecoder{

	@Override
	protected Object decode(ChannelHandlerContext ctx, Channel channel,
			Object msg) throws Exception {
		System.out.println("######ClientReadDecoder");
		
		byte[] buffer = ((ChannelBuffer)msg).array();
		byte last = buffer[buffer.length - 1];
		// 46 is '.'
		if(last == 46)
			return new String(buffer, CharsetUtil.UTF_8);
		return null;
	}
}

package com.sean.client.handler;

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.string.StringEncoder;
import org.jboss.netty.util.CharsetUtil;

public class ClientWriteEncoder extends StringEncoder{

	@Override
	protected Object encode(ChannelHandlerContext ctx, Channel channel,
			Object msg) throws Exception {
		System.out.println("######ClientWriteEncoder");
		
		String str = (String)msg;
		ChannelBuffer channelBuffer = 
				ChannelBuffers.copiedBuffer(str, CharsetUtil.UTF_8);
		return channelBuffer;
	}
}

运行结果如下：

Server端后台日志：

Server is started...
1257526899
######channelConnected
[id: 0x88120865, /127.0.0.1:58887 => /127.0.0.1:8000]
######ServerReadDecoder
######messageReceived
The message sent by client is : Hi, Server.
######ServerWriteEncoder
The message has sent to client.
Server is stopped.

Client端后台日志：

1767582956
Client is started...
######channelConnected
######ClientWriteEncoder
######writeComplete
######ClientReadDecoder
######messageReceived
The message gotten from server is : Hi, Client.