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AbstractBootstrap是一个工具类，用来配置和启动Channel的，下面看下AbstractBootstrap的类继承，ServerBootstrap用于启动ServerChannel的，是服务端的工具类，Bootstrap是用于启动Channel，是客户端的工具类，bind用于udp等无连接的传输，bind用于有连接的传输。
AbstractBootstrap
该类用来配置启动一个Channel,那么配置启动一个Channel需要那些条件？首先需要一个Channel，AbstractBootstrap提供了一个ChannelFactory对象用来创建Channel,一个Channel会对应一个EventLoop用于IO的事件处理，在Channel的整个生命周期中会绑定一个EventLoop,这里可理解给Channel分配一个线程进行IO事件处理，结束后回收该线程，但是AbstractBootstrap没有提供EventLoop而是提供了一个EventLoopGroup，EventLoop继承EventLoopGroup，在某些情况下可以把EventLoopGroup当EventLoop来用，EventLoopGroup中包含多个Eventloop，当一个连接到达，Netty会注册一个Channel，然后EventLoopGroup会分配一个EventLoop绑定到这个channel。不管是服务器还是客户端的Channel都需要绑定一个本地端口这就有了SocketAddress类的对象localAddress，Channel有很多选项所有有了options对象LinkedHashMap
private volatile EventLoopGroup group;private volatile ChannelFactory channelFactory;private volatile SocketAddress localAddress;private final Map, Object> options = new LinkedHashMap, Object>();private final Map, Object> attrs = new LinkedHashMap, Object>();private volatile ChannelHandler handler;
AbstractBootstrap还有一个重要方法doBind(),为什么这个方法会在父类实现而不是在ServerBootstrap中实现,注解里面写了bind()方法不仅可以在ServerBootstrap中绑定一个端口用于监听，也可以用在BootStrap中用于无连接的数据传输。这里主要调用Channel的bind方法。因为netty中多有的操作都是异步的。所以所有IOC操作都返回future的子类。然后判断是否OK，有时间写一篇该文章。
Bootstrap
客户端的帮助类，用来配置启动一个channel,该类有2个主要方法，一个init用于初始化通道，一个是doConnect(),这里面会生成一个客户端的Channel。
private ChannelFuture doConnect(final SocketAddress remoteAddress, final SocketAddress localAddress) {final ChannelFuture regFuture = initAndRegister();final Channel channel = regFuture.channel();if (regFuture.cause() != null) {return regFuture;}final ChannelPromise promise = channel.newPromise();if (regFuture.isDone()) {doConnect0(regFuture, channel, remoteAddress, localAddress, promise);} else {regFuture.addListener(new ChannelFutureListener() {@Overridepublic void operationComplete(ChannelFuture future) throws Exception {doConnect0(regFuture, channel, remoteAddress, localAddress, promise);}});}return promise;}
EventLoopGroup group = new NioEventLoopGroup();try {Bootstrap b = new Bootstrap();b.group(group).channel(NioSocketChannel.class).option(ChannelOption.TCP_NODELAY, true).handler(new ChannelInitializer<SocketChannel>() {@Overridepublic void initChannel(SocketChannel ch) throws Exception {ChannelPipeline p = ch.pipeline();if (sslCtx != null) {p.addLast(sslCtx.newHandler(ch.alloc(), HOST, PORT));}//p.addLast(new LoggingHandler(LogLevel.INFO));p.addLast(new EchoClientHandler());}});// Start the client.ChannelFuture f = b.connect(HOST, PORT).sync(); //// Wait until the connection is closed.f.channel().closeFuture().sync();} finally {// Shut down the event loop to terminate all threads.group.shutdownGracefully();}
private final Map<ChannelOption<?>, Object> childOptions = new LinkedHashMap<ChannelOption<?>, Object>();private final Map<AttributeKey<?>, Object> childAttrs = new LinkedHashMap<AttributeKey<?>, Object>();private volatile EventLoopGroup childGroup;private volatile ChannelHandler childHandler;
p.addLast(new ChannelInitializer<Channel>() { //当有Channel连接该监听端口是调用该@Overridepublic void initChannel(Channel ch) throws Exception {ch.pipeline().addLast(new ServerBootstrapAcceptor(currentChildGroup, currentChildHandler, currentChildOptions, currentChildAttrs));}});
EventLoopGroup bossGroup = new NioEventLoopGroup(1);EventLoopGroup workerGroup = new NioEventLoopGroup();try {ServerBootstrap b = new ServerBootstrap();b.group(bossGroup, workerGroup)/*** 设置服务端的Channel,Netty通过Channel工厂类创建不同的Channel,对于服务端，* Netty需要创建NioServerSocketChannel,*/.channel(NioServerSocketChannel.class)/*** 设置TCP的参数，这里设置了套接字的最大连接个数。*/.option(ChannelOption.SO_BACKLOG, 100)/*** 设置父类的Handler,父类的handler是客户端新接入的接连SocketChannel对应的ChannelPipeline* 的handler*/.handler(new LoggingHandler(LogLevel.INFO))/*** 子类的Hanlder是NioServerSockerChannel对应的ChannelPipeline的Handler*//*** 区别：ServerBootstrap中的handler是NioServerSocketChannel使用* 所有连接该监听端口的客户端都会执行它，父类的AbstractBootstrap中的Handler* 是个工厂类，他为没有新接入的客户端都创建一个新的Handler*/.childHandler(new ChannelInitializer<SocketChannel>() {@Overridepublic void initChannel(SocketChannel ch) throws Exception {ChannelPipeline p = ch.pipeline();if (sslCtx != null) {p.addLast(sslCtx.newHandler(ch.alloc()));}//p.addLast(new LoggingHandler(LogLevel.INFO));p.addLast(new EchoServerHandler());}});/***每个channel绑定一个ChannelPipeline，一个ChannelPipeline里面添加了很多handler*/// Start the server.ChannelFuture f = b.bind(PORT).sync();// Wait until the server socket is closed.f.channel().closeFuture().sync();} finally {// Shut down all event loops to terminate all threads.bossGroup.shutdownGracefully();workerGroup.shutdownGracefully();}
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原文地址：http://www.cnblogs.com/gaoxing/p/4384784.html
