netty源码分析之客户端

一、前言

上篇博客介绍了服务端的启动源码,这篇就开始介绍客户端

二、源码分析

首先贴上客户端的简单代码~

public class SocketClient {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(eventLoopGroup).channel(NioSocketChannel.class).handler(new LoggingHandler(LogLevel.INFO))
                    .handler(new SocketClientInitializer());

            ChannelFuture channelFuture = bootstrap.connect("localhost", 7878).sync();
            channelFuture.channel().closeFuture().sync();
        } finally {
            eventLoopGroup.shutdownGracefully();
        }
    }
}

设置group和server端不同的是,这里这设置一个group

public B group(EventLoopGroup group) {
    if (group == null) {
        throw new NullPointerException("group");
    }
    if (this.group != null) {
        throw new IllegalStateException("group set already");
    }
    this.group = group;
    return (B) this;
}

设置channel

public B channel(Class channelClass) {
    if (channelClass == null) {
        throw new NullPointerException("channelClass");
    }
    // server端使用的是ReflectiveChannelFactory
    // 最后newChannel()后面也是通过反射来实现的了
    return channelFactory(new BootstrapChannelFactory(channelClass));
}

设置handler

@SuppressWarnings("unchecked")
public B handler(ChannelHandler handler) {
    if (handler == null) {
        throw new NullPointerException("handler");
    }
    this.handler = handler;
    return (B) this;
}

接着就是核心代码连接了

public ChannelFuture connect(String inetHost, int inetPort) {
    return connect(new InetSocketAddress(inetHost, inetPort));
}
public ChannelFuture connect(SocketAddress remoteAddress) {
    if (remoteAddress == null) {
        throw new NullPointerException("remoteAddress");
    }
    validate();
    return doConnect(remoteAddress, localAddress());
}
// 这部分代码和server绑定类似
private ChannelFuture doConnect(final SocketAddress remoteAddress, final SocketAddress localAddress) {
    // 初始化和注册channel
    final ChannelFuture regFuture = initAndRegister();
    // 获取channel
    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 {
        // 为future添加一个监听器
        regFuture.addListener(new ChannelFutureListener() {
            @Override
            public void operationComplete(ChannelFuture future) throws Exception {
                doConnect0(regFuture, channel, remoteAddress, localAddress, promise);
            }
        });
    }

    return promise;
}
final ChannelFuture initAndRegister() {
    // 创建channel
    final Channel channel = channelFactory().newChannel();
    try {
        // 初始化channel
        init(channel);
    } catch (Throwable t) {
        channel.unsafe().closeForcibly();
        return channel.newFailedFuture(t);
    }
    // 注册channel
    ChannelFuture regFuture = group().register(channel);
    if (regFuture.cause() != null) {
        if (channel.isRegistered()) {
            channel.close();
        } else {
            channel.unsafe().closeForcibly();
        }
    }
    return regFuture;
}
//Bootstrap channel初始化部分
void init(Channel channel) throws Exception {
    // 获取通道
    ChannelPipeline p = channel.pipeline();
    // 为通道添加handler,这里的handler就是我们添加的ChannelInitializer类
    p.addLast(handler());
    // 下面的一些配置就不是很重要的了
    final Map, Object> options = options();
    synchronized (options) {
        for (Entry, Object> e: options.entrySet()) {
            try {
                if (!channel.config().setOption((ChannelOption