Netty系列-客户端启动源码分析

客户端的示例代码

package com.netty.server;import io.netty.bootstrap.Bootstrap;import io.netty.buffer.ByteBuf;import io.netty.buffer.Unpooled;import io.netty.channel.*;import io.netty.channel.nio.NioEventLoopGroup;import io.netty.channel.socket.SocketChannel;import io.netty.channel.socket.nio.NioSocketChannel;import io.netty.handler.codec.LineBasedFrameDecoder;import io.netty.handler.codec.string.StringDecoder;/** * Created by lcq on 12/5/2016. */public class NettyTimeClient {    public static void main(String[] args) {        int port = 8080;        try {            new NettyTimeClient().connect(port, "127.0.0.1");        } catch (InterruptedException e) {            e.printStackTrace();        }    }    private void connect(int port, String host) throws InterruptedException {        EventLoopGroup group = new NioEventLoopGroup();//与服务端不同，客户端只需要一个IO线程组        try {            Bootstrap b = new Bootstrap();            b.group(group).channel(NioSocketChannel.class).option(ChannelOption.TCP_NODELAY, true).handler(new ChannelInitializer<SocketChannel>() {//设置channel类型为NioSocketChannel                @Override                protected void initChannel(SocketChannel sc) throws Exception {//初始化时添加handler                    sc.pipeline().addLast(new LineBasedFrameDecoder(1024));                    sc.pipeline().addLast(new StringDecoder());                    sc.pipeline().addLast(new TimeClientHandler2());                }            });            ChannelFuture f = b.connect(host,port).sync();            f.channel().closeFuture().sync();        } finally {            group.shutdownGracefully();        }    }    private class TimeClientHandler2 extends ChannelHandlerAdapter {        private ByteBuf firtMessage;        private int counter;        private byte[] req = null;        public TimeClientHandler2(){            req = ("QUERY TIME ORDER" + System.getProperty("line.separator")).getBytes();        }        @Override        public void channelActive(ChannelHandlerContext ctx) throws Exception {            for (int i = 0;i < 100;i++){                firtMessage = Unpooled.buffer(req.length);                firtMessage.writeBytes(req);                ctx.writeAndFlush(firtMessage);            }        }        @Override        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {            String body = (String)msg;            System.out.println("Now is : " + body + " ; the counter is : " + ++counter);        }        @Override        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {            ctx.close();        }    }}

客户端Bootstrap的配置过程和服务端ServerBootstrap配置过程类似，不再细看。

看一下connect过程

    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());    }

    private ChannelFuture doConnect(final SocketAddress remoteAddress, final SocketAddress localAddress) {        final ChannelFuture regFuture = initAndRegister();//和服务端类似，初始化并注册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 {            regFuture.addListener(new ChannelFutureListener() {                @Override                public void operationComplete(ChannelFuture future) throws Exception {                    doConnect0(regFuture, channel, remoteAddress, localAddress, promise);                }            });        }        return promise;    }

    final ChannelFuture initAndRegister() {        Channel channel;        try {            channel = createChannel();//用之前设置的channel工厂，创建channel，此处是NioSocketChannel        } catch (Throwable t) {            return VoidChannel.INSTANCE.newFailedFuture(t);        }        try {            init(channel);//init方法客户端实现是和server不同的        } catch (Throwable t) {            channel.unsafe().closeForcibly();            return channel.newFailedFuture(t);        }        ChannelPromise regFuture = channel.newPromise();        channel.unsafe().register(regFuture);//向NioEventLoopGroup中注册这个channel        if (regFuture.cause() != null) {            if (channel.isRegistered()) {                channel.close();            } else {                channel.unsafe().closeForcibly();            }        }        // If we are here and the promise is not failed, it's one of the following cases:        // 1) If we attempted registration from the event loop, the registration has been completed at this point.        //    i.e. It's safe to attempt bind() or connect() now beause the channel has been registered.        // 2) If we attempted registration from the other thread, the registration request has been successfully        //    added to the event loop's task queue for later execution.        //    i.e. It's safe to attempt bind() or connect() now:        //         because bind() or connect() will be executed *after* the scheduled registration task is executed        //         because register(), bind(), and connect() are all bound to the same thread.        return regFuture;    }

客户端的init方法

    void init(Channel channel) throws Exception {        ChannelPipeline p = channel.pipeline();        p.addLast(handler());        final Map<ChannelOption<?>, Object> options = options();        synchronized (options) {            for (Entry<ChannelOption<?>, Object> e: options.entrySet()) {                try {                    if (!channel.config().setOption((ChannelOption<Object>) e.getKey(), e.getValue())) {                        logger.warn("Unknown channel option: " + e);                    }                } catch (Throwable t) {                    logger.warn("Failed to set a channel option: " + channel, t);                }            }        }        final Map<AttributeKey<?>, Object> attrs = attrs();        synchronized (attrs) {            for (Entry<AttributeKey<?>, Object> e: attrs.entrySet()) {                channel.attr((AttributeKey<Object>) e.getKey()).set(e.getValue());            }        }    }

和服务端类似，设置handler，设置选项和属性。

接下来是register，和服务端是一样的。

直接看connect方法

    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() {                @Override                public void operationComplete(ChannelFuture future) throws Exception {                    doConnect0(regFuture, channel, remoteAddress, localAddress, promise);                }            });        }        return promise;    }

    private static void doConnect0(            final ChannelFuture regFuture, final Channel channel,            final SocketAddress remoteAddress, final SocketAddress localAddress, final ChannelPromise promise) {        // This method is invoked before channelRegistered() is triggered.  Give user handlers a chance to set up        // the pipeline in its channelRegistered() implementation.        channel.eventLoop().execute(new Runnable() {            @Override            public void run() {                if (regFuture.isSuccess()) {                    if (localAddress == null) {                        channel.connect(remoteAddress, promise);                    } else {                        channel.connect(remoteAddress, localAddress, promise);//connect连接操作异步执行，会在eventloop中循环接收连接完成的结果                    }                    promise.addListener(ChannelFutureListener.CLOSE_ON_FAILURE);                } else {                    promise.setFailure(regFuture.cause());                }            }        });    }

    public ChannelFuture connect(SocketAddress remoteAddress, SocketAddress localAddress, ChannelPromise promise) {        return pipeline.connect(remoteAddress, localAddress, promise);    }

    public ChannelFuture connect(SocketAddress remoteAddress, SocketAddress localAddress, ChannelPromise promise) {        return tail.connect(remoteAddress, localAddress, promise);    }

顺着handler调用链一直往前找会到head handler，即HeadHandler

        public void connect(                ChannelHandlerContext ctx,                SocketAddress remoteAddress, SocketAddress localAddress,                ChannelPromise promise) throws Exception {            unsafe.connect(remoteAddress, localAddress, promise);        }

        public void connect(                final SocketAddress remoteAddress, final SocketAddress localAddress, final ChannelPromise promise) {            if (!ensureOpen(promise)) {                return;            }            try {                if (connectPromise != null) {                    throw new IllegalStateException("connection attempt already made");                }                boolean wasActive = isActive();                if (doConnect(remoteAddress, localAddress)) {                    fulfillConnectPromise(promise, wasActive);                } else {                    connectPromise = promise;                    requestedRemoteAddress = remoteAddress;                    // Schedule connect timeout.                    int connectTimeoutMillis = config().getConnectTimeoutMillis();                    if (connectTimeoutMillis > 0) {                        connectTimeoutFuture = eventLoop().schedule(new Runnable() {                            @Override                            public void run() {                                ChannelPromise connectPromise = AbstractNioChannel.this.connectPromise;                                ConnectTimeoutException cause =                                        new ConnectTimeoutException("connection timed out: " + remoteAddress);                                if (connectPromise != null && connectPromise.tryFailure(cause)) {                                    close(voidPromise());                                }                            }                        }, connectTimeoutMillis, TimeUnit.MILLISECONDS);                    }                    promise.addListener(new ChannelFutureListener() {                        @Override                        public void operationComplete(ChannelFuture future) throws Exception {                            if (future.isCancelled()) {                                if (connectTimeoutFuture != null) {                                    connectTimeoutFuture.cancel(false);                                }                                connectPromise = null;                                close(voidPromise());                            }                        }                    });                }            } catch (Throwable t) {                if (t instanceof ConnectException) {                    Throwable newT = new ConnectException(t.getMessage() + ": " + remoteAddress);                    newT.setStackTrace(t.getStackTrace());                    t = newT;                }                promise.tryFailure(t);                closeIfClosed();            }        }

看一下fulfillConnectPromise方法

        private void fulfillConnectPromise(ChannelPromise promise, boolean wasActive) {            // trySuccess() will return false if a user cancelled the connection attempt.            boolean promiseSet = promise.trySuccess();            // Regardless if the connection attempt was cancelled, channelActive() event should be triggered,            // because what happened is what happened.            if (!wasActive && isActive()) {//连接成功，执行read                pipeline().fireChannelActive();            }            // If a user cancelled the connection attempt, close the channel, which is followed by channelInactive().            if (!promiseSet) {                close(voidPromise());            }        }

    public ChannelPipeline fireChannelActive() {        head.fireChannelActive();        if (channel.config().isAutoRead()) {            channel.read();        }        return this;    }

触发read后，开始按照顺序执行：pipeline.read()-->tail.read()-->****-->head.read()-->unsafe.beginRead()-->doBeginRead()-->real操作