netty组件

1. Channel组件

核心的针对BIO/NIO提供的抽象的网络通道，支持读，写，连接和绑定。

Channel

A nexus to a network socket or a component which is capable of I/O operations such as read, write, connect, and bind. 

ChannelFactory

Creates a Channel associated with a certain communication entity such as a network socket. 

2. ChannelPipeline组件

可以理解为ChannelHandler的容器，主要负责通道的可读，可写，连接和绑定等事件在管道化的一系列ChannelHandler中的流转。所有ChannelHandler都必须注册到ChannelPipeline中按顺序组织起来。

ChannelPipeline

A list of ChannelHandlers which handles or interceptsChannelEvents of aChannel.  

ChannelPipelineFactory

Creates a new ChannelPipeline for a newChannel.  

3. ChannelHandler组件

提供针对通道的可读，可写，连接和绑定等事件的处理接口，主要负责实际与网络IO无关的业务逻辑的处理。

ChannelHandler

Handles or intercepts a ChannelEvent, and sends aChannelEvent to the next handler in aChannelPipeline.  

ChannelHandlerContext

Enables a ChannelHandler to interact with itsChannelPipeline and other handlers.

4. ChannelFuture组件

针对通道的读，写，连接和绑定等异步IO操作的抽象，类似于JDK中提供的Future。一个ChannelFuture对象代表了一个尚未发生的I/O操作。这意味着，任何已请求的操作都可能是没有被立即执行的，因为在Netty内部所有的操作都是异步的。

ChannelFuture

The result of an asynchronous Channel I/O operation. 

ChannelFutureListener

Listens to the result of a ChannelFuture. 

5. ChannelBuffer组件

Netty中的buffer是完全重新实现的，与NIO ByteBuffer完全不同。如果要说NIO的Buffer和Netty的ChannelBuffer最大的区别的话，就是前者仅仅是传输上的Buffer，而后者其实是传输Buffer和抽象后的逻辑Buffer的结合。

ChannelBuffer

A random and sequential accessible sequence of zero or more bytes (octets). This interface provides an abstract view for one or more primitive byte arrays (byte[]) andNIO buffers. 

6. ChannelEvent组件

ChannelEvent是数据或者状态的载体，当对Channel进行操作时，会产生一个ChannelEvent，并发送到ChannelPipeline。

ChannelEvent

An I/O event or I/O request associated with a Channel.

A ChannelEvent is handled by a series of ChannelHandlers in a ChannelPipeline.

Netty是什么？

本质：JBoss做的一个Jar包

目的：快速开发高性能、高可靠性的网络服务器和客户端程序

优点：提供异步的、事件驱动的网络应用程序框架和工具

通俗的说：一个好使的处理Socket的东东

Netty的特性

设计

统一的API，适用于不同的协议（阻塞和非阻塞）

基于灵活、可扩展的事件驱动模型

高度可定制的线程模型

可靠的无连接数据Socket支持（UDP）

性能

更好的吞吐量，低延迟

更省资源

尽量减少不必要的内存拷贝

安全

完整的SSL/TLS和STARTTLS的支持

能在Applet与Android的限制环境运行良好

健壮性

不再因过快、过慢或超负载连接导致OutOfMemoryError

不再有在高速网络环境下NIO读写频率不一致的问题

易用

完善的JavaDoc，用户指南和样例

简洁简单

下面提供一个简单的例子

第一步：下载netty5.0

移步官网下载 http://netty.io/downloads.html或者

使用maven，在pom.xml中添加如下代码

<dependency>    <groupId>io.netty</groupId>    <artifactId>netty-all</artifactId>    <version>5.0.0.Alpha2</version></dependency>

第二步： 编写Server端代码

NettyServerBootstrap代码

import java.util.concurrent.TimeUnit;import org.apache.log4j.Logger;import io.netty.bootstrap.ServerBootstrap;import io.netty.channel.ChannelFuture;import io.netty.channel.ChannelInitializer;import io.netty.channel.ChannelOption;import io.netty.channel.ChannelPipeline;import io.netty.channel.EventLoopGroup;import io.netty.channel.nio.NioEventLoopGroup;import io.netty.channel.socket.SocketChannel;import io.netty.channel.socket.nio.NioServerSocketChannel;import io.netty.handler.codec.LengthFieldBasedFrameDecoder;import io.netty.handler.timeout.IdleStateHandler;public class NettyServerBootstrap {private static Logger logger = Logger.getLogger(NettyServerBootstrap.class);private int port;public NettyServerBootstrap(int port) {this.port = port;bind();}private void bind() {EventLoopGroup boss = new NioEventLoopGroup();EventLoopGroup worker = new NioEventLoopGroup();try {ServerBootstrap bootstrap = new ServerBootstrap();bootstrap.group(boss, worker);bootstrap.channel(NioServerSocketChannel.class);bootstrap.option(ChannelOption.SO_BACKLOG, 1024); //连接数bootstrap.option(ChannelOption.TCP_NODELAY, true);  //不延迟，消息立即发送bootstrap.childOption(ChannelOption.SO_KEEPALIVE, true); //长连接bootstrap.childHandler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel socketChannel)throws Exception {ChannelPipeline p = socketChannel.pipeline();p.addLast(new NettyServerHandler());}});ChannelFuture f = bootstrap.bind(port).sync();if (f.isSuccess()) {logger.debug("启动Netty服务成功，端口号：" + this.port);}// 关闭连接f.channel().closeFuture().sync();} catch (Exception e) {logger.error("启动Netty服务异常，异常信息：" + e.getMessage());e.printStackTrace();} finally {boss.shutdownGracefully();worker.shutdownGracefully();}}public static void main(String[] args) throws InterruptedException {NettyServerBootstrap server= new NettyServerBootstrap(9999);}}

NettyServerHandler代码

import java.io.UnsupportedEncodingException;import com.datong.base.module.netty.common.Constant;import io.netty.buffer.ByteBuf;import io.netty.buffer.Unpooled;import io.netty.channel.ChannelHandlerAdapter;import io.netty.channel.ChannelHandlerContext;public class NettyServerHandler extends ChannelHandlerAdapter {@Overridepublic void channelRead(ChannelHandlerContext ctx, Object msg) {ByteBuf buf = (ByteBuf) msg;String recieved = getMessage(buf);System.out.println("服务器接收到消息：" + recieved);try {ctx.writeAndFlush(getSendByteBuf("APPLE"));} catch (UnsupportedEncodingException e) {e.printStackTrace();}}/* * 从ByteBuf中获取信息 使用UTF-8编码返回 */private String getMessage(ByteBuf buf) {byte[] con = new byte[buf.readableBytes()];buf.readBytes(con);try {return new String(con, Constant.UTF8);} catch (UnsupportedEncodingException e) {e.printStackTrace();return null;}}private ByteBuf getSendByteBuf(String message)throws UnsupportedEncodingException {byte[] req = message.getBytes("UTF-8");ByteBuf pingMessage = Unpooled.buffer();pingMessage.writeBytes(req);return pingMessage;}}

第三步：编写Client代码

NettyClient代码

import java.util.concurrent.TimeUnit;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;import io.netty.handler.codec.LengthFieldBasedFrameDecoder;import io.netty.handler.timeout.IdleStateHandler;public class NettyClient {/* * 服务器端口号 */private int port;/* * 服务器IP */private String host;public NettyClientBootstrap(int port, String host)throws InterruptedException {this.port = port;this.host = host;start();}private void start() throws InterruptedException {EventLoopGroup eventLoopGroup = new NioEventLoopGroup();try {Bootstrap bootstrap = new Bootstrap();bootstrap.channel(NioSocketChannel.class);bootstrap.option(ChannelOption.SO_KEEPALIVE, true);bootstrap.group(eventLoopGroup);bootstrap.remoteAddress(host, port);bootstrap.handler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel socketChannel)throws Exception {socketChannel.pipeline().addLast(new NettyClientHandler());}});ChannelFuture future = bootstrap.connect(host, port).sync();if (future.isSuccess()) {socketChannel = (SocketChannel) future.channel();System.out.println("----------------connect server success----------------");}future.channel().closeFuture().sync();} finally {eventLoopGroup.shutdownGracefully();}}public static void main(String[] args) throws InterruptedException {NettyClient client = new NettyClient(9999,"localhost");}}

NettyClientHandler代码

import java.text.SimpleDateFormat;import java.util.Date;import java.util.concurrent.TimeUnit;import com.netty.common.NettyStartRunable;import com.netty.common.ProxyPool;import com.netty.util.JsonUtil;import net.sf.json.JSONObject;import io.netty.buffer.ByteBuf;import io.netty.buffer.Unpooled;import io.netty.channel.ChannelHandlerAdapter;import io.netty.channel.ChannelHandlerContext;public class NettyClientHandler extends ChannelHandlerAdapter  {private  ByteBuf firstMessage;@Overridepublic void channelActive(ChannelHandlerContext ctx) throws Exception {byte[] data = "服务器，给我一个APPLE".getBytes();firstMessage=Unpooled.buffer();firstMessage.writeBytes(data);ctx.writeAndFlush(firstMessage);}@Overridepublic void channelRead(ChannelHandlerContext ctx, Object msg)throws Exception {ByteBuf buf = (ByteBuf) msg;String rev = getMessage(bug);System.out.println("客户端收到服务器数据:" + rev);}private String getMessage(ByteBuf buf) {byte[] con = new byte[buf.readableBytes()];buf.readBytes(con);try {return new String(con, Constant.UTF8);} catch (UnsupportedEncodingException e) {e.printStackTrace();return null;}}}