java - Netty的future.channel().closeFuture().sync();到底有什么用？

问题描述

我看到很多Netty的例子都在末尾加上了这句话：future.channel().closeFuture().sync();

比如:

public class TimeServer { private int count = 0; public void bind(int port) {try { EventLoopGroup bossGroup = new NioEventLoopGroup(); EventLoopGroup workGroup = new NioEventLoopGroup(); ServerBootstrap b = new ServerBootstrap(); // (2) b.group(bossGroup, workGroup).channel(NioServerSocketChannel.class) // (3) .childHandler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel arg0) throws Exception { arg0.pipeline().addLast(new LineBasedFrameDecoder(1024)); arg0.pipeline().addLast(new StringDecoder()); arg0.pipeline().addLast(new ChannelInboundHandlerAdapter() {@Overridepublic void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { // ByteBuf buf = (ByteBuf) msg; // byte[] req = new // byte[buf.readableBytes()]; // buf.readBytes(req); // String body = new String(req, 'UTF-8'); System.out.println( 'The Time Server Received order:' + msg + '; the counter is:' + ++count); // String currentTime = 'QUERY TIME // ORDER'.equalsIgnoreCase(body) // ? new // Date(System.currentTimeMillis()).toString() // : 'BAD ORDER'; // // currentTime = currentTime + // System.getProperty('line.separator'); // ByteBuf resp = // Unpooled.copiedBuffer(currentTime.getBytes()); // ctx.writeAndFlush(resp);} });} }); ChannelFuture future = b.bind(port).sync(); System.out.println('Server start listen at ' + port); future.channel().closeFuture().sync();System.out.println('执行到这里 ' + port);} catch (InterruptedException e) { e.printStackTrace();} } public static void main(String[] args) {new TimeServer().bind(10000); }}

但是我看这行代码一直没有执行。请问这是怎么回事呢？

问题解答

不是没执行，是主线程到这里就 wait 子线程退出了，子线程才是真正监听和接受请求的。