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【第15篇】netty服务端初始化流程详细分析

2019-05-28  本文已影响20人  爱学习的蹭蹭

1、 Channel与ChannelHandlerContext

New and noteworthy in 4.1 请截图

ChannelHandlerContext
ChannelHandlerContext

2、 初始化流程

服务端初始化的步骤
1、创建ServerBootstrap启动辅助类，通过Builder模式进行参数配置；
2、创建并绑定Reactor线程池EventLoopGroup；
4、设置并绑定服务端Channel通道类型；
5、绑定服务端通道数据处理器责任链Handler；

3、ServerBootstrap初始化

public class ServerBootstrap extends AbstractBootstrap<ServerBootstrap, ServerChannel> {
    private final Map<ChannelOption<?>, Object> childOptions = new LinkedHashMap();
    private final Map<AttributeKey<?>, Object> childAttrs = new LinkedHashMap();
    private final ServerBootstrapConfig config = new ServerBootstrapConfig(this);
    private volatile EventLoopGroup childGroup;
    private volatile ChannelHandler childHandler;
}
image.png 
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();
ServerBootstrap b= new ServerBootstrap();
b.group(boosGroup,workGroup)


public ServerBootstrap group(EventLoopGroup group) {
    return this.group(group, group);
}

public ServerBootstrap group(EventLoopGroup parentGroup, EventLoopGroup childGroup) {
    super.group(parentGroup);
    if(childGroup == null) {
        throw new NullPointerException("childGroup");
    } else if(this.childGroup != null) {
        throw new IllegalStateException("childGroup set already");
    } else {
        this.childGroup = childGroup;
        return this;
    }
}

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

4、Channel通道初始化

public B channel(Class<? extends C> channelClass) {
    if(channelClass == null) {
        throw new NullPointerException("channelClass");
    } else {
        return this.channelFactory((io.netty.channel.ChannelFactory)(new ReflectiveChannelFactory(channelClass)));
    }
}


private final Class<? extends T> clazz;

public ReflectiveChannelFactory(Class<? extends T> clazz) {
    if(clazz == null) {
        throw new NullPointerException("clazz");
    } else {
        this.clazz = clazz;
    }
}

public T newChannel() {
    try {
        return (Channel)this.clazz.newInstance();
    } catch (Throwable var2) {
        throw new ChannelException("Unable to create Channel from class " + this.clazz, var2);
    }
}

public B channelFactory(ChannelFactory<? extends C> channelFactory) {
    if(channelFactory == null) {
        throw new NullPointerException("channelFactory");
    } else if(this.channelFactory != null) {
        throw new IllegalStateException("channelFactory set already");
    } else {
        this.channelFactory = channelFactory;
        return this;
    }
}

5、Channel通道实例化

ServerBootstrap.bind() -> AbstractBootstrap.doBind() -> AbstractBootstrap.initAndRegister() -> ChannelFactory.newChannel();

public T newChannel() {
    try {
        return (Channel)this.clazz.newInstance();
    } catch (Throwable var2) {
        throw new ChannelException("Unable to create Channel from class " + this.clazz, var2);
    }
}

public NioServerSocketChannel() {
    this(newSocket(DEFAULT_SELECTOR_PROVIDER));
}

public NioServerSocketChannel(java.nio.channels.ServerSocketChannel channel) {
    super((Channel)null, channel, 16);
    this.config = new NioServerSocketChannel.NioServerSocketChannelConfig(this, this.javaChannel().socket());
}

AbstractNioChannel 中的属性:

AbstractChannel 的属性:

NioServerSocketChannel 中的属性:

ServerSocketChannelConfig config = new NioServerSocketChannelConfig(this, javaChannel().socket())

6、Channel通道注册

final ChannelFuture initAndRegister() {
    // 去掉非关键代码
    final Channel channel = channelFactory().newChannel();
    init(channel);
    ChannelFuture regFuture = group().register(channel);
}

private void register0(ChannelPromise promise) {
    boolean firstRegistration = neverRegistered;
    doRegister();
    neverRegistered = false;
    registered = true;
    safeSetSuccess(promise);
    pipeline.fireChannelRegistered();
    // 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 (firstRegistration && isActive()) {
        pipeline.fireChannelActive();
    }
}

@Override
protected void doRegister() throws Exception {
    // 省略错误处理
    selectionKey = javaChannel().register(eventLoop().selector, 0, this);
}

7 handler处理器的添加过程

bootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
                    @Override
 protected void initChannel(SocketChannel socketChannel) throws Exception {
    socketChannel.pipeline().addLast(new TimeServerHandler());
     }
});

public ServerBootstrap childHandler(ChannelHandler childHandler) {
    if(childHandler == null) {
        throw new NullPointerException("childHandler");
    } else {
        this.childHandler = childHandler;
        return this;
    }
}

@Override
void init(Channel channel) throws Exception {
    ...
    ChannelPipeline p = channel.pipeline();

    final EventLoopGroup currentChildGroup = childGroup;
    final ChannelHandler currentChildHandler = childHandler;
    final Entry<ChannelOption<?>, Object>[] currentChildOptions;
    final Entry<AttributeKey<?>, Object>[] currentChildAttrs;

    p.addLast(new ChannelInitializer<Channel>() {
        @Override
        public void initChannel(Channel ch) throws Exception {
            ChannelPipeline pipeline = ch.pipeline();
            ChannelHandler handler = handler();
            if (handler != null) {
                pipeline.addLast(handler);
            }
            pipeline.addLast(new ServerBootstrapAcceptor(
                    currentChildGroup, currentChildHandler, currentChildOptions, currentChildAttrs));
        }
    });
}

public void channelRead(ChannelHandlerContext ctx, Object msg) {
    final Channel child = (Channel) msg;
    child.pipeline().addLast(childHandler);
    ...
    childGroup.register(child).addListener(...);
}

8、 OIO（掌握点）

9、 lsof命令

10、总结

Netty服务端的初始化主要是创建初始化辅助类ServerBootstrap，并对辅助类的相关参数进行初始化包括EventLoop线程池，Channle通道类型和ChannleHandler通道处理器等；在调用bind()方法进行端口绑定时，会根据ServerBootsrap中的初始化参数启动服务端，具体的启动流程为：

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