Netty入门实例及分析

浏览数：19 / 时间：2015年06月09日

什么是netty？下面是官方文档的简介：
The Netty project  is an effort to provide an asynchronous event-driven network application framework and tools for rapid development of maintainable high performance and high scalability protocol servers and clients. In other words, Netty is a NIO client server framework which enables quick and easy development of network applications such as protocol servers and clients. It greatly simplifies and streamlines network programming such as TCP/IP socket server.

下面写一个简单的实例：
1.客户端细节分析

ChannelFactory是创建一个通道（和一次具体的通信实体关联如网络套接字）的主要接口，比如NioServerSocketChannelFactory 会创建一个Channel，有基于NIO的服务套接字作为底层的通信实体。一旦一个新的通道创建，那么对应的ChannelPipeline就会开始处理相关的ChannelEvents。
 

NioClientSocketChannelFactory会创建一个客户端的基于NIO的SocketChannel，利用非阻塞IO模型来高效处理这些并发的连接。其中有两种类型的线程， boss thread 和 worker thread，每个NioClientSocketChannelFactory 有一个boss thread，它主要是有请求要发出时试图进行一次连接，连接成功后，将这个连接的通道交付给一个worker thread，接下来这个worker thread 为一个或多个通道执行非阻塞的读写服务。


ClientBootstrap只是一个辅助函数，不会分配或者管理任何资源，管理资源是由构造器中指定的ChannelFactory完成的。所以从同一个ChannelFactory衍生出多个ClientBootstrap是可以的，从而为不同的Channel应用不同的设置。connect（）方法会根据指定的SocketAddress试图建立连接，如果本地地址没有设置，就会自动分配，等价于：
ClientBootstrap b = ....;
b.connect(remoteAddress, b.getOption("localAddress"));


静态方法 Channels.pipeline(ChannelHandler... handlers)用参数所指定的ChannelHandler 来创建一个新的ChannelPipeline，当然它们是有顺序的，我们也可以自己一个一个的添加。
 public static ChannelPipeline pipeline(ChannelHandler... handlers) {
        if (handlers == null) {
            throw new NullPointerException( "handlers");
        }

        ChannelPipeline newPipeline = pipeline ();
        for (int i = 0; i < handlers. length; i ++) {
            ChannelHandler h = handlers[i];
            if (h == null) {
                break;
            }
            newPipeline.addLast(ConversionUtil. toString(i), h);
        }
        return newPipeline;
    }

2. 服务器端细节分析

服务器端构建的基本流程和客户端类似，只是这里的ChannelFactory，Bootstrap 都要满足作为server的特性。
NioServerSocketChannelFactory创建服务器端的，基于NIO的ServerSocketChannel，仍然是非阻塞模式。
每个绑定的ServerSocketChannel 有自身的boos thread，比如说打开监听了两个端口 80,443，那么就会有两个boss thread，各自负责各自端口的连接请求，直到那个端口解绑定，然后将接受的连接请求交给worker thread去处理。

这里是面向连接传输的ClientBootstrap 和  ServerBootstrap ，如果想用UDP的话就选 ConnectionlessBootstrap。

3. ChannelHandler的常见用法就会根据具体的事件类型做出具体的处理，牵扯到读写管道，而且有上下流的情况。

一个简单的netty例子：
TimeClientl.java
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;

public class TimeClient {
	public static void main(String[] args) {
		String host = args[0];
		int port = Integer.parseInt(args[1]);
		
		ChannelFactory factory = new NioClientSocketChannelFactory(
				Executors.newCachedThreadPool(), Executors.newCachedThreadPool());
		ClientBootstrap bootstrap = new ClientBootstrap(factory);
		bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
			@Override
			public ChannelPipeline getPipeline() throws Exception {
				return Channels.pipeline(new TimeClientHandler2());
			}
		});
		bootstrap.connect(new InetSocketAddress(host, port));  //
	}

}


TimeClientHandler.java
import java.util.Date;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ExceptionEvent;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelHandler;

public class TimeClientHandler extends SimpleChannelHandler{
	@Override
	public void messageReceived(ChannelHandlerContext ctx, MessageEvent e)
			throws Exception {
		ChannelBuffer buffer = (ChannelBuffer)e.getMessage();
		long currentTimeMills = buffer.readInt() * 1000L;
		System.out.println(new Date(currentTimeMills));
		e.getChannel().close();
	}
	
	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e)
			throws Exception {
		e.getCause().printStackTrace();
		Channel c = e.getChannel();
		c.close();
	}
}



TimeServer.java
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.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.channel.Channels;
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 TimeServer {
	public static ChannelGroup allChannels = new DefaultChannelGroup("time-server");
	
	public static void main(String[] args) {
		ChannelFactory factory = new NioServerSocketChannelFactory(
				Executors.newCachedThreadPool(),
				Executors.newCachedThreadPool());
		
		ServerBootstrap bootstrap = new ServerBootstrap(factory);
		bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
			@Override
			public ChannelPipeline getPipeline() throws Exception {
				return Channels.pipeline(new TimeServerHandler2(),
										 new TimeEncoder());
			}
		});
		
		bootstrap.setOption("reuseAddr", true);
		bootstrap.setOption("child.tcpNoDelay", true);
		bootstrap.setOption("child.keepAlive", true);
		
		Channel channel = bootstrap.bind(new InetSocketAddress(8080));
		
		allChannels.add(channel);
		//waitForShutdownCommand();  this is a imaginary logic:for instance 
		//when there is accepted connection we close this server ;
		if(allChannels.size() >=2){
			ChannelGroupFuture f = allChannels.close();
			f.awaitUninterruptibly();
			factory.releaseExternalResources();
		}
	}
}



TimeServerHandler.java
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
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.SimpleChannelHandler;

public class TimeServerHandler extends SimpleChannelHandler{
	@Override
	public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e)
			throws Exception {
		Channel ch = e.getChannel();
		ChannelBuffer time = ChannelBuffers.buffer(4); //sizeof int
		time.writeInt((int)(System.currentTimeMillis()/1000L + 2208988800L));
		
		ChannelFuture cf = ch.write(time);
		cf.addListener(new ChannelFutureListener() {
			@Override
			public void operationComplete(ChannelFuture future) throws Exception {
				Channel ch = future.getChannel();
				ch.close();
			}
		});
	}
	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e)
			throws Exception {
		e.getCause().printStackTrace();
		Channel c = e.getChannel();
		c.close();
	}
}



Netty入门实例及分析,古老的榕树,5-wow.com

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标签： netty clientbootstrap serverbootstrap channel netty clientbootstrap serverbootstrap channel

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