Netty Serial 1：入门应用

一：Netty简介
  Netty是目前最流行的NIO框架之一，它的健壮性、功能、性能、可定制性和扩展性在同类框架中都是首屈一指的，目前流行的Hadoop的RPC框架avro使用Netty作为底层通信框架，它的主要优点有：
1、开发门槛低；
2、功能强大，支持多种主流协议；
3、性能高，成熟稳定；
4、定制能力强。

二：Netty入门应用
  本节以时间服务器为例进行开发，客户端发送一个命令请求，服务器端接受命令返回当前日期给客户端，本节主要包括的内容有：
1、环境搭建
2、服务器端开发
3、客户端开发
4、测试

1、环境搭建：
  可以通过maven来构建，也可以直接将netty的jar包导入到classpath中。
  maven构建：
  <dependency>
        <groupId>io.netty</groupId>
        <artifactId>netty-all</artifactId>
        <version>5.0.0.Alpha2</version>
  </dependency>
 
  jar包方式：到官网http://netty.io/downloads.html下载相应的开发包，解压，将\%nettyhome%\jar\all-in-one\目录下的jar导入到classpath即可

2、服务器端开发

TimeServer：时间服务器

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;

public class TimeServer {
	public void bind(int port) {
		EventLoopGroup bossGroup = new NioEventLoopGroup();
		EventLoopGroup workerGroup = new NioEventLoopGroup();
		try {
			ServerBootstrap bootstrap = new ServerBootstrap();
			bootstrap.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class)
					.option(ChannelOption.SO_BACKLOG, 1024).childHandler(new ChildChannelHandler());

			ChannelFuture f = bootstrap.bind(port).sync();

			f.channel().closeFuture().sync();
		} catch (Exception e) {
			// TODO: handle exception
		} finally {
			bossGroup.shutdownGracefully();
			workerGroup.shutdownGracefully();
		}
	}

	public static void main(String[] args) {
		new TimeServer().bind(8080);
	}
}

class ChildChannelHandler extends ChannelInitializer<SocketChannel> {
	@Override
	protected void initChannel(SocketChannel arg0) throws Exception {
		// TODO Auto-generated method stub
		arg0.pipeline().addLast(new TimeServerHandler());
	}
}

TimeServerHandler：时间服务端处理器

import java.util.Date;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;

public class TimeServerHandler extends ChannelHandlerAdapter{

	@Override
	public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
		// TODO Auto-generated method stub
		ByteBuf buf = (ByteBuf) msg;
		byte[] req = new byte[buf.readableBytes()];
		buf.readBytes(req);
		String body = new String(req, "UTF-8");
		System.out.println("the time server receive order :" + body);
		String currentyTime = "QUERY TIME ORDER".equalsIgnoreCase(body)?new Date(System.currentTimeMillis()).toString():"BAD ORDER";
		ByteBuf copiedBuffer = Unpooled.copiedBuffer(currentyTime.getBytes());
		ctx.write(copiedBuffer);
	}
	
	@Override
	public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
		// TODO Auto-generated method stub
		ctx.flush();	
	}
	
	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
		// TODO Auto-generated method stub
		ctx.close();
	}
}

3、客户端开发

TimeClient:客户端

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;

public class TimeClient {

	public void connect(String host,int port){
		EventLoopGroup group = new NioEventLoopGroup();
		try {
			Bootstrap bootstrap = new Bootstrap();
			bootstrap.group(group).channel(NioSocketChannel.class)
			.option(ChannelOption.TCP_NODELAY, true).handler(new ChannelInitializer<SocketChannel>() {
				protected void initChannel(SocketChannel s) throws Exception {
					
					s.pipeline().addLast(new TimeClienHandler());
				};
			});
				ChannelFuture f = bootstrap.connect(host, port).sync();
			
			f.channel().closeFuture().sync();
		} catch (Exception e) {
			// TODO: handle exception
		} finally {
			group.shutdownGracefully();
		}
	}
	public static void main(String[] args) {
		new TimeClient().connect("127.0.0.1", 8080);
	}
}

TimeClienHandler：时间客户端处理器

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;

public class TimeClienHandler extends ChannelHandlerAdapter {

	private final ByteBuf buf;

	public TimeClienHandler() {
		byte[] req = "QUERY TIME ORDER".getBytes();
		buf = Unpooled.buffer(req.length);
		buf.writeBytes(req);
	}

	@Override
	public void channelActive(ChannelHandlerContext ctx) throws Exception {
		// TODO Auto-generated method stub
		ctx.writeAndFlush(buf);
	}

	@Override
	public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
		// TODO Auto-generated method stub
		ByteBuf buf = (ByteBuf) msg;
		byte[] req = new byte[buf.readableBytes()];
		buf.readBytes(req);
		String body = new String(req, "UTF-8");
		System.out.println("now is :" + body);
	}

	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
		// TODO Auto-generated method stub
		ctx.close();
	}
}

4、测试
先运行服务器TimeServer，然后运行TimeClient
服务器端收到:
the time server receive order :QUERY TIME ORDER

客户端收到：
now is :Fri Sep 18 10:05:36 CST 2015