ServerBootstrap创建
ServerBootstrap 为 netty 建立服务端的辅助类, 以 NIO为例，创建代码如下：
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public static void main(String[] args) throws Exception { ServerBootstrap bs = new ServerBootstrap(); bs.group(new NioEventLoopGroup(1), new NioEventLoopGroup()) .channel(NioServerSocketChannel.class) .childHandler(new ChannelInitializer<Channel>() { @Override protected void initChannel(Channel ch) throws Exception { ch.pipeline() .addLast(new HttpServerCodec()) .addLast(new HttpObjectAggregator(65535)) .addLast(new Controller()); } }).bind(8080).sync().channel().closeFuture().sync(); } |
核心参数
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//配置属性，如 SO_KEEPALIVE 等private final ServerBootstrapConfig config = new ServerBootstrapConfig(this); //acceot 的 子channel所绑定的 事件循环组" private volatile EventLoopGroup childGroup; private volatile ChannelHandler childHandler; |
初始化流程
主要为 绑定本地端口 -> 注册自身到 EventLoop ， 并注册 accept 和 read 事件 -> EventLoop的主循环中会不断的select注册的channel的事件，并处理。
首先执行绑定
核心逻辑位于
io.netty.bootstrap.AbstractBootstrap.doBind(SocketAddress) 和 io.netty.bootstrap.AbstractBootstrap.initAndRegister()中
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private ChannelFuture doBind(final SocketAddress localAddress) { final ChannelFuture regFuture = initAndRegister(); ..........if (regFuture.isDone()) { // At this point we know that the registration was complete and successful. ChannelPromise promise = channel.newPromise(); //绑定逻辑 doBind0(regFuture, channel, localAddress, promise); return promise; } else { // Registration future is almost always fulfilled already, but just in case it's not. final PendingRegistrationPromise promise = new PendingRegistrationPromise(channel); regFuture.addListener(new ChannelFutureListener() { @Override public void operationComplete(ChannelFuture future) throws Exception { Throwable cause = future.cause(); if (cause != null) { // Registration on the EventLoop failed so fail the ChannelPromise directly to not cause an // IllegalStateException once we try to access the EventLoop of the Channel. promise.setFailure(cause); } else { // Registration was successful, so set the correct executor to use. // See https://github.com/netty/netty/issues/2586 promise.registered(); doBind0(regFuture, channel, localAddress, promise); } } }); return promise; } } |
注册自身到 EventLoop
先来看 initAndRegister ， 核心逻辑就是利用channelFactory初始化一个NioServerSocketChannel实例，并为其设置上config中的参数，然后将其注册到EventLoop中，实际上是委托的channel的Unsafe来实现注册的，核心逻辑位于 AbstractUnsafe.register0 中 完成注册
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final ChannelFuture initAndRegister() { Channel channel = null; try { //本例子中实际调用的是 NioServerSocketChannel的构造参数， 并为其设置感兴趣的事件类型为 OP_ACCEPT channel = channelFactory.newChannel(); init(channel); } catch (Throwable t) { if (channel != null) { // channel can be null if newChannel crashed (eg SocketException("too many open files")) channel.unsafe().closeForcibly(); } // as the Channel is not registered yet we need to force the usage of the GlobalEventExecutor return new DefaultChannelPromise(channel, GlobalEventExecutor.INSTANCE).setFailure(t); } ChannelFuture regFuture = config().group().register(channel); if (regFuture.cause() != null) { if (channel.isRegistered()) { channel.close(); } else { channel.unsafe().closeForcibly(); } } return regFuture; } |
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void init(Channel channel) throws Exception { //设置属性 .......... 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() { //为NioServerSocketChannel 设置一个 默认的 channelhandler ： ServerBootstrapAcceptor ， 当发生 accept事件时，将 accept的channel注册到 childEventLoop中 pipeline.addLast(new ServerBootstrapAcceptor( ch, currentChildGroup, currentChildHandler, currentChildOptions, currentChildAttrs)); } }); } }); } |
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private void register0(ChannelPromise promise) { try { // check if the channel is still open as it could be closed in the mean time when the register // call was outside of the eventLoop if (!promise.setUncancellable() || !ensureOpen(promise)) { return; } boolean firstRegistration = neverRegistered; //执行channel到 eventloop的 selector doRegister(); neverRegistered = false; registered = true; // Ensure we call handlerAdded(...) before we actually notify the promise. This is needed as the // user may already fire events through the pipeline in the ChannelFutureListener. pipeline.invokeHandlerAddedIfNeeded(); safeSetSuccess(promise); |
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//触发 InboundChannelHnader.channelRegistered 事件 pipeline.fireChannelRegistered(); |
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// Only fire a channelActive if the channel has never been registered. This prevents firing // multiple channel actives if the channel is deregistered and re-registered. if (isActive()) { if (firstRegistration) { //触发channelActive事件，并会为 channel 绑定上 read 事件 pipeline.fireChannelActive(); } else if (config().isAutoRead()) { // This channel was registered before and autoRead() is set. This means we need to begin read // again so that we process inbound data. // // See https://github.com/netty/netty/issues/4805 beginRead(); } } } catch (Throwable t) { // Close the channel directly to avoid FD leak. closeForcibly(); closeFuture.setClosed(); safeSetFailure(promise, t); } } |
绑定端口逻辑
initAndRegister注册成功后,开始执行真正的绑定端口逻辑，核心逻辑位于 NioSocketChannel.doBind0(SocketAddress) 中
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private void doBind0(SocketAddress localAddress) throws Exception { if (PlatformDependent.javaVersion() >= 7) { SocketUtils.bind(javaChannel(), localAddress); } else { SocketUtils.bind(javaChannel().socket(), localAddress); } } |
至此 绑定个成功， 当触发 ACCEPT 事件时， 会触发 NioServerSocketChannel.doReadMessages -> ServerBootstrapAcceptor.channelRead , 并将 子channel 注册到 childEventLoop中
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public void channelRead(ChannelHandlerContext ctx, Object msg) { final Channel child = (Channel) msg; child.pipeline().addLast(childHandler); setChannelOptions(child, childOptions, logger); for (Entry<AttributeKey<?>, Object> e: childAttrs) { child.attr((AttributeKey<Object>) e.getKey()).set(e.getValue()); } try { //注册channel childGroup.register(child).addListener(new ChannelFutureListener() { @Override public void operationComplete(ChannelFuture future) throws Exception { if (!future.isSuccess()) { forceClose(child, future.cause()); } } }); } catch (Throwable t) { forceClose(child, t); } } |
以上就是netty服务端辅助类ServerBootstrap创建逻辑分析的详细内容，更多关于netty辅助类ServerBootstrap创建逻辑的资料请关注服务器之家其它相关文章！
原文链接：https://www.cnblogs.com/ironroot/p/8581065.html
