java - Netty Http Client : how to separate client-start,发送请求，和client-shutdown分为不同的方法

Question

1。背景
我发现大多数使用 Netty 的 http 客户端示例似乎都遵循以下代码结构:

public void run() {
    EventLoopGroup group = new NioEventLoopGroup();
    try {
        Bootstrap b = new Bootstrap();
        b.group(group)
         .channel(NioSocketChannel.class)
         .handler(new HttpSnoopClientInitializer(sslCtx));

        // Make the connection attempt.
        Channel ch = b.connect(host, port).sync().channel();
        // send something
        ch.writeAndFlush(XXXX);
        // Wait for the server to close the connection.
        ch.closeFuture().sync();
    } finally {
        // Shut down executor threads to exit.
        group.shutdownGracefully();
    }
}

所以如果我理解正确的话，每次发送请求时，我都需要创建一个客户端，并在其上调用client.run()。也就是说，我似乎一次只能提出一个“固定”请求。

2.我的需求
我需要一个可以发送多个请求的长期客户。更具体地说，会有另一个线程向客户端发送指令，客户端每次收到指令后，都会发送一个请求。像这样:

Client client = new Client();
client.start();

client.sendRequest(request1);
client.sendRequest(request2);
...
client.shutDownGracefully(); // not sure if this shutdown is necessary or not
// because I need a long-standing client to wait for instructions to send requests
// in this sense it's kinda like a server.

3.我试过的
我试过这样的事情:from this link

public MyClient(String host, int port) {
    System.out.println("Initializing client and connecting to server..");
    EventLoopGroup workerGroup = new NioEventLoopGroup();

    Bootstrap b = new Bootstrap();
    b.group(workerGroup)
        .channel(NioSocketChannel.class)
        .option(ChannelOption.SO_KEEPALIVE, true)
        .handler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel channel) throws Exception {
                channel.pipeline().addLast(new StringDecoder());
                channel.pipeline().addLast(new StringEncoder());
                channel.pipeline().addLast(new MyAppClientHandler());
            }
        });

    channelFuture = b.connect(host, port);
}

public ResponseFuture send(final String msg) {
    final ResponseFuture responseFuture = new ResponseFuture();

    channelFuture.addListener(new GenericFutureListener<ChannelFuture>() {
        @Override
        public void operationComplete(ChannelFuture future)
                throws Exception {
            channelFuture.channel().pipeline().get(MyAppClientHandler.class).setResponseFuture(responseFuture);
            channelFuture.channel().writeAndFlush(msg);                             
        }
    });

    return responseFuture;
}

public void close() {
    channelFuture.channel().close();        
}

问题是这段代码似乎没有调用 workerGroup.shutDownGracefully()，所以我猜这可能有问题。有没有办法将“启动客户端”、“发送请求”、“关闭客户端”分成不同的方法？提前致谢!

Answer 1

最简单的解决方案是使用 netty 提供的 ChannelPool:https://netty.io/news/2015/05/07/4-0-28-Final.html

它提供开箱即用的 gracefulshutdown、maxconnections 等。