如何在Netty中使用多个ServerBootstrap对象

下面的示例您引用并添加了关于sync()方法的问题,这里是一个示例代码:

EventLoopGroup bossGroup = new NioEventLoopGroup(numBossThreads);
EventLoopGroup workerGroup = new NioEventLoopGroup(numWorkerThreads);
ServerBootstrap sb1 = null;
ServerBootstrap sb2 = null;
ServerBootstrap sb3 = null;
Channel ch1 = null;
Channel ch2 = null;
Channel ch3 = null;
try {
    sb1 = new ServerBootstrap();
    sb1.group(bossGroup, workerGroup);
    ...
    ch1 = sb1.bind().sync().channel();

    sb2 = new ServerBootstrap();
    sb2.group(bossGroup, workerGroup);
    ...
    ch2 = sb2.bind().sync().channel();

    sb3 = new ServerBootstrap();
    sb3.group(bossGroup, workerGroup);
    ...
    ch3 = sb3.bind().sync().channel();
} finally {
    // Now waiting for the parent channels (the binded ones) to be closed
    if (ch1 != null) {
        ch1.closeFuture().sync();
    }
    if (b1 != null) {
        b1.shutdownGracefully();
    }
    if (ch2 != null) {
        ch2.closeFuture().sync();
    }
    if (b2 != null) {
        b2.shutdownGracefully();
    }
    if (ch3 != null) {
        ch3.closeFuture().sync();
    }
    if (b3 != null) {
        b3.shutdownGracefully();
    }

所以现在解释(我尝试):

该bind()命令创建侦听对应的套接字.它立即返回(不阻塞),因此父通道可能尚未可用.

第一个sync()命令(bind().sync())等待绑定完成(如果引发异常,则直接转到finally部分).在此阶段,通道已准备就绪,并确保侦听新连接.

该channel()命令获取此侦听通道(父通道,尚未连接到任何人).所有客户端都将生成此父级的"子"通道.

在您的处理程序中,在某个事件之后,您决定关闭父通道(不是子通道,而是侦听并等待新套接字的通道).要做到这一点,只需打电话parentChannel.close()(或从儿童频道child.parent().close()).

该closeFuture()命令是关闭此事件的未来.

当这个未来结束(完成)时,这是最后一个sync()命令(closeFuture().sync())发生的时间.

关闭父通道后,您可以要求正常关闭绑定通道.

所以这样做(等待closeFuture然后shutdownGracefully)是一种干净的方法来关闭附加到这个ServerBootstrap的所有资源.

当然你可以改变一些事情.例如,没有先获取通道,但只有在优先关闭之前要阻塞时才能获得通道.

EventLoopGroup bossGroup = new NioEventLoopGroup(numBossThreads);
EventLoopGroup workerGroup = new NioEventLoopGroup(numWorkerThreads);
ServerBootstrap sb1 = null;
ServerBootstrap sb2 = null;
ServerBootstrap sb3 = null;
ChannelFuture cf1 = null;
ChannelFuture cf2 = null;
ChannelFuture cf3 = null;
try {
    sb1 = new ServerBootstrap();
    sb1.group(bossGroup, workerGroup);
    ...
    cf1 = sb1.bind();

    sb2 = new ServerBootstrap();
    sb2.group(bossGroup, workerGroup);
    ...
    cf2 = sb2.bind();

    sb3 = new ServerBootstrap();
    sb3.group(bossGroup, workerGroup);
    ...
    cf3 = sb3.bind();
} finally {
    // Now waiting for the parent channels (the binded ones) to be closed
    if (cf1 != null) {
        cf1.sync().channel().closeFuture().sync();
    }
    if (cf2 != null) {
        c2.sync().channel().closeFuture().sync();
    }
    if (cf3 != null) {
        cf3.sync().channel().closeFuture().sync();
    }
    if (b1 != null) {
        b1.shutdownGracefully();
    }
    if (b2 != null) {
        b2.shutdownGracefully();
    }
    if (b3 != null) {
        b3.shutdownGracefully();
    }

这样你在打开所有3个通道时根本不会阻塞,但是在关闭它们之前等待所有3个通道完成.

最后,如果您没有阻止bind()事件然后在closeFuture()事件上,sbx.bind()则由您来定义在命令之后和关闭ServerBootstraps之前等待的方式.