EventLoopGroup bossGroup = new NioEventLoopGroup(); // (1)
//負責資料讀寫
EventLoopGroup workerGroup = new NioEventLoopGroup();
//服務類
try {
ServerBootstrap bootstrap = new ServerBootstrap();
//reactor模型接收和處理
bootstrap.group(bossGroup, workerGroup)
//channelFactory屬性為ReflectiveChannelFactory通過反射建立NioServerSocketChannel對象
.channel(NioServerSocketChannel.class) // (3)
.childHandler(new ChannelInitializer<SocketChannel>() { // (4)
@Override
public void initChannel(SocketChannel ch) throws Exception {
ch.pipeline().addLast(new DiscardServerHandler());
}
})
//完成三次握手後等待隊列的大小,超過了則拒絕,預設50
.option(ChannelOption.SO_BACKLOG, 128) // (5)
.childOption(ChannelOption.SO_KEEPALIVE, true); // (6)
// Bind and start to accept incoming connections.
ChannelFuture f = bootstrap.bind(5555).sync(); 就從啟動bind()方法開始進入到
AbstractBootstrap 
然後進入dobind方法
private ChannelFuture doBind(final SocketAddress localAddress) {
//傳回DefaultChannelPromise,注冊線程池到channel
final ChannelFuture regFuture = initAndRegister();
final Channel channel = regFuture.channel();
if (regFuture.cause() != null) {
return regFuture;
}
if (regFuture.isDone()) {
// At this point we know that the registration was complete and successful.
//在這一點上，我們知道注冊是完整和成功的
ChannelPromise promise = channel.newPromise();
doBind0(regFuture, channel, localAddress, promise);
return promise;
} else {
省略。。。。。
}
} 然後我們先執行,在這邊建立channel，然後先init初始化,傳回到
final ChannelFuture initAndRegister() {
Channel channel = null;
try {
//建立之前設定的NioServerSocketChannel對象
channel = channelFactory.newChannel();
//服務端,初始化channel屬性,并且設定pipeline,建立ServerBootstrapAcceptor
//用戶端ChannelInitializer初始化
init(channel);
} catch (Throwable t) {
大緻就是注冊失敗,我們注冊到全局線程去執行
}
//ServerBootstrapConfig裡面放了ServerBootstrap,獲得線程池最後到SingleThreadEventLoop裡面把線程池注冊給channel
//我們建立的channel的pipeline也在這裡加入
ChannelFuture regFuture = config().group().register(channel);
if (regFuture.cause() != null) {
if (channel.isRegistered()) {
channel.close();
} else {
channel.unsafe().closeForcibly();
}
}
return regFuture;
} 調用這裡面的init()方法,主要就是設定channel屬性和初始化一個ChannelInitializer
void init(Channel channel) throws Exception {
final Map<ChannelOption<?>, Object> options = options0();
synchronized (options) {
//之前填的屬性射到channel裡
setChannelOptions(channel, options, logger);
}
省略。。。。
ChannelPipeline p = channel.pipeline();
省略。。。。
//查到head與tail之間,後面會初始化這個ChannelInitializer
p.addLast(new ChannelInitializer<Channel>() {
@Override
public void initChannel(final Channel ch) throws Exception {
final ChannelPipeline pipeline = ch.pipeline();
ChannelHandler handler = config.handler();
if (handler != null) {
pipeline.addLast(handler);
}
ch.eventLoop().execute(new Runnable() {
@Override
public void run() {
pipeline.addLast(new ServerBootstrapAcceptor(
ch, currentChildGroup, currentChildHandler, currentChildOptions, currentChildAttrs));
}
});
}
});
} 上面執行完了傳回到AbstractBootstrap的initAndRegister方法,接着執行這個
//ServerBootstrapConfig裡面放了ServerBootstrap,獲得線程池最後到SingleThreadEventLoop裡面把線程池注冊給channel
//我們建立的channel的pipeline也在這裡加入
ChannelFuture regFuture = config().group().register(channel); 先去MultithreadEventLoopGroup的方法裡面選出一個線程池
public ChannelFuture register(Channel channel) {
return next().register(channel);
} 最後到AbstractChannel的方法裡面去注冊,這個promise就是傳回用來做sync()的東西,這裡一個線程池就一個線程
public final void register(EventLoop eventLoop, final ChannelPromise promise) {
。。。。。
AbstractChannel.this.eventLoop = eventLoop;
//是否啟動這個線程池
if (eventLoop.inEventLoop()) {
//注冊channel到select,同時設定promise完成
register0(promise);
} else {
try {
//送出并且啟動線程池
eventLoop.execute(new Runnable() {
@Override
public void run() {
register0(promise);
}
});
} catch (Throwable t) {
。。。。。。
}
}
}
然後調用register0方法
private void register0(ChannelPromise promise) {
try {
//AbstractNioChannel的方法,注冊到select
doRegister();
//調用回調函數
pipeline.invokeHandlerAddedIfNeeded();
//設定promise完成,避免阻塞
safeSetSuccess(promise);
//把ChannelInitializer的東西添加到pipeline
pipeline.fireChannelRegistered();
//如果通道從未注冊過，則隻啟用通道激活。如果通道被撤銷注冊并重新注冊，這将防止觸發多個通道活動。
if (isActive()) {
if (firstRegistration) {
pipeline.fireChannelActive();
} else if (config().isAutoRead()) {
。。。。。
//設定讀,還有感興趣的東西accept之類的
beginRead();
}
}
} catch (Throwable t) {
。。。。。
}
}
進去doRegister看看
protected void doRegister() throws Exception {
boolean selected = false;
for (;;) {
try {
//把channel注冊到selector裡面,但為什麼是個0呢傳回之後增加興趣事件
selectionKey = javaChannel().register(eventLoop().unwrappedSelector(), 0, this);
return;
} catch (CancelledKeyException e) {
if (!selected) {
eventLoop().selectNow();
selected = true;
} else {
throw e;
}
}
}
} 傳回上一個register0方法這邊初始化剛才添加的管道調用initlize方法,網管道裡面加上一個ServerBootstrapAcceptor
因為管道是分為inbond和outbond的讀取和輸出的時候要搞清楚
//把ChannelInitializer的東西添加到pipeline
pipeline.fireChannelRegistered(); 傳回上一個register0方法,在這邊注冊讀感興趣
//設定讀,還有感興趣的東西accept之類的
beginRead(); 然後這邊運作完了就傳回到doBind方法
private static void doBind0(
final ChannelFuture regFuture, final Channel channel,
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.
//這個方法在channelregister()被觸發之前被調用。給使用者處理程式一個機會，在它的通道注冊()實作中設定管道
//獲得NioEventLoop裡面的線程池
channel.eventLoop().execute(new Runnable() {
@Override
public void run() {
if (regFuture.isSuccess()) {
//到AbstractChannel裡面,經過pipeline最後應該是給實際的channel注冊位址吧
channel.bind(localAddress, promise).addListener(ChannelFutureListener.CLOSE_ON_FAILURE);
} else {
promise.setFailure(regFuture.cause());
}
}
});
} 然後弄完了再傳回就完成了服務端啟動了
![Netty4 2_ChannelInitializer[圖]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)