通過Netty中的ServerBootstrap ChannelPipeline發送消息時出現UnsupportedOperationException

Question

我正在使用Netty 5.0。

我有一個補充的客戶端引導程序，我從netty github上獲取了SecureChatClient.java示例。 我將消息從客戶端引導程序發送到服務器，它工作正常。 當我嘗試將消息從服​​務器引導程序發送到客戶端時（首先通過客戶端成功啟動連接/通道之后），我得到一個java.lang.UnsupportedOperationException沒有任何進一步的信息。 從服務器向客戶端發送消息是通過上面的代碼完成的。

服務器引導程序僅用於接收嗎？

是不是如上所述，serverbootstrap是否能夠將消息寫回到客戶端？ 我的意思是，消息可以從套接字通過ChannelHandlers進入ChannelPipeline，但是只有ChannelHandlers應該將響應寫回ChannelPipeline並退出套接字。 因此，在ServerBootstrap中，用戶並不意味着能夠從管道外部沿ChannelPipeline發送消息。 （希望如此）

還是我只是想念一些東西？

我的代碼如下：

    // Ports.
    int serverPort = 8080;

    EventLoopGroup bossGroup    = new NioEventLoopGroup();
    EventLoopGroup workerGroup  = new NioEventLoopGroup();
    try {
        ServerBootstrap b = new ServerBootstrap();
        b.group(bossGroup, workerGroup)
         .channel(NioServerSocketChannel.class)
         .childHandler(new ChannelInitializer<SocketChannel>() {
             @Override
             public void initChannel(SocketChannel ch) throws Exception {
                 ch.pipeline().addLast("MyMessageHandler", new MyMessageHandler());
             }
         })
         .option(ChannelOption.SO_BACKLOG, 128)
         .childOption(ChannelOption.SO_KEEPALIVE, true);

        // Bind and start to accept incoming connections.
        ChannelFuture f = b.bind(serverPort).sync();
        Channel ch = f.channel();

        System.out.println("Server: Running!");

      // Read commands from the stdin.
      ChannelFuture lastWriteFuture = null;
      BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
      while(true)
      {
          String line = in.readLine();
          if (line == null) break;

          ByteBuf getOut = buffer(64);
          getOut.writeBytes(line.getBytes());

          // Sends the received line to the server.
          lastWriteFuture = ch.writeAndFlush(getOut);

          lastWriteFuture.addListener(new ChannelFutureListener() {
                @Override
                public void operationComplete(ChannelFuture cf) throws Exception {
                    if(cf.isSuccess()) {
                        System.out.println("CFListener: SUCCESS! YEAH! HELL! YEAH!");
                    } else {
                        System.out.println("CFListener: failure! FAILure! FAILURE!");
                        System.out.println(cf.cause());
                    }
                }
            });

      }

               // Wait until all messages are flushed before closing the channel.
      if (lastWriteFuture != null) {
          lastWriteFuture.sync();
      }


        // Wait until the server socket is closed.
        // In this example, this does not happen, but you can do that to gracefully
        // shut down your server.
        f.channel().closeFuture().sync();
    } catch (InterruptedException | UnsupportedOperationException e) {
        e.printStackTrace();
    } finally {
        workerGroup.shutdownGracefully();
        bossGroup.shutdownGracefully();
    }

我開始使用以下示例： https : //github.com/netty/netty/tree/4.1/example/src/main/java/io/netty/example/securechat

我的問題是調用ch.writeAndFlush時出現以下異常：

java.lang.UnsupportedOperationException
at io.netty.channel.socket.nio.NioServerSocketChannel.filterOutboundMessage(NioServerSocketChannel.java:184)
at io.netty.channel.AbstractChannel$AbstractUnsafe.write(AbstractChannel.java:784)
at io.netty.channel.DefaultChannelPipeline$HeadContext.write(DefaultChannelPipeline.java:1278)
at io.netty.channel.ChannelHandlerInvokerUtil.invokeWriteNow(ChannelHandlerInvokerUtil.java:158)
at io.netty.channel.DefaultChannelHandlerInvoker$WriteTask.run(DefaultChannelHandlerInvoker.java:440)
at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:328)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:354)
at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116)
at io.netty.util.internal.chmv8.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1412)
at io.netty.util.internal.chmv8.ForkJoinTask.doExec(ForkJoinTask.java:280)
at io.netty.util.internal.chmv8.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:877)
at io.netty.util.internal.chmv8.ForkJoinPool.scan(ForkJoinPool.java:1706)
at io.netty.util.internal.chmv8.ForkJoinPool.runWorker(ForkJoinPool.java:1661)
at io.netty.util.internal.chmv8.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:126)

Answer 1

您無法寫入ServerChannel，只能連接到普通通道。 由於這個原因，您對writeAndFlush調用失敗。

要將消息發送給每個客戶端，您應該將每個客戶端的通道存儲在ChannelGroup中，並在其上調用writeAndFlush（）。

一種快速的方法是在ServerBootstrap中添加另一個處理程序，該處理程序將傳入的連接置於ChannelGroup內，這的快速實現是：

// In your main:
ChannelGroup allChannels =
         new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);

// In your ChannelInitializer<SocketChannel>
ch.pipeline().addLast("grouper", new GlobalSendHandler());

// New class:
public class MyHandler extends ChannelInboundHandlerAdapter {
     @Override
     public void channelActive(ChannelHandlerContext ctx) {
         allChannels.add(ctx.channel());
         super.channelActive(ctx);
     }
 }

然后我們可以調用以下命令向每個連接發送消息，這將返回ChannelGroupFuture而不是普通的ChannelFuture ：

allChannels.writeAndFlush(getOut);

上面的修復程序使您的總代碼看起來像這樣：

// Ports.
int serverPort = 8080;

ChannelGroup allChannels =
         new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);

EventLoopGroup bossGroup    = new NioEventLoopGroup();
EventLoopGroup workerGroup  = new NioEventLoopGroup();
try {
    ServerBootstrap b = new ServerBootstrap();
    b.group(bossGroup, workerGroup)
     .channel(NioServerSocketChannel.class)
     .childHandler(new ChannelInitializer<SocketChannel>() {
         @Override
         public void initChannel(SocketChannel ch) throws Exception {
             ch.pipeline().addLast("MyMessageHandler", new MyMessageHandler());
             ch.pipeline().addLast("grouper", new GlobalSendHandler());
         }
     })
     .option(ChannelOption.SO_BACKLOG, 128)
     .childOption(ChannelOption.SO_KEEPALIVE, true);

    // Bind and start to accept incoming connections.
    ChannelFuture f = b.bind(serverPort).sync();
    Channel ch = f.channel();

    System.out.println("Server: Running!");

  // Read commands from the stdin.
  ChannelGroupFuture lastWriteFuture = null;
  BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
  while(true)
  {
      String line = in.readLine();
      if (line == null) break;

      ByteBuf getOut = buffer(64);
      getOut.writeBytes(line.getBytes());

      // Sends the received line to the server.
      lastWriteFuture = allChannels.writeAndFlush(getOut);

      lastWriteFuture.addListener(new ChannelGroupFutureListener() {
            @Override
            public void operationComplete(ChannelGroupFuture cf) throws Exception {
                if(cf.isSuccess()) {
                    System.out.println("CFListener: SUCCESS! YEAH! HELL! YEAH!");
                } else {
                    System.out.println("CFListener: failure! FAILure! FAILURE!");
                    System.out.println(cf.cause());
                }
            }
        });

  }

           // Wait until all messages are flushed before closing the channel.
  if (lastWriteFuture != null) {
      lastWriteFuture.sync();
  }


    // Wait until the server socket is closed.
    // In this example, this does not happen, but you can do that to gracefully
    // shut down your server.
    f.channel().closeFuture().sync();
} catch (InterruptedException | UnsupportedOperationException e) {
    e.printStackTrace();
} finally {
    workerGroup.shutdownGracefully();
    bossGroup.shutdownGracefully();
}

Answer 2

我認為Netty Server沒有解碼器，編碼器。 如果要發送字符串數據，

serverBootstrap.group(bossGroup, workerGroup).childHandler(new ChannelInitializer<SocketChannel>() {
    @Override
    protected void initChannel(SocketChannel channel) throws Exception {
        ChannelPipeline channelPipeline = channel.pipeline();
        channelPipeline.addLast("String Encoder", new StringEncoder(CharsetUtil.UTF_8));
        channelPipeline.addLast("String Decoder", new StringDecoder(CharsetUtil.UTF_8));
    }
});

添加服務器的初始化器！