为什么是ChannelHandlerContext。writeAndFlush（）不处理我的字符串？

Question

我使用Netty 4.1.16创建一个服务器。我建立一个管道：

socketChannel.pipeline()
        //Line Based Frame Decoder will split a message into frames separated by CR/LF.
        // This one discards the delimiter and fails on excessive length only when the
        // entire frame has been read.
        .addLast("Frame Decoder", new LineBasedFrameDecoder(MAX_FRAME_LENGTH, true, false))
        // String decoder changes inbound byte stream into a string.
        .addLast("String Decoder", new StringDecoder(CharsetUtil.US_ASCII))
        // VoiceMessage is a custom decoder that turns a string into a socket message
        // and passes it to a command handler thread.
        .addLast("VoiceMessage Decoder", new InboundVoiceHandler())
        // String encoder allows us to write a string directly to the channel without needing
        // to write a custom string-to-byte encoder.
        .addLast("String Encoder", new StringEncoder(CharsetUtil.US_ASCII));

在稍后的代码中，我将创建一个对传入消息的字符串响应，并尝试使用以下命令将其写入ChannelHandlerContext：

    message = pack.getBoardList() == null || pack.getBoardList().size() > 0
            ? "Existing pack number " + pack.getPackNo() + " has been recalled."
            : "New pack number " + pack.getPackNo() + " has been started.";
    new OutboundTalkmanMessage(channelHandlerContext, voiceMessage.getVoiceSession())
            .writeAndFlush(message, vdtsSysDB);

...

public class OutboundTalkmanMessage {
    private VoiceSession voiceSession;
    private ChannelHandlerContext ctx;

    private static final Logger LOG = LoggerFactory.getLogger(OutboundTalkmanMessage.class);

    public OutboundTalkmanMessage(ChannelHandlerContext ctx, VoiceSession voiceSession) {
        this.ctx = ctx;
        this.voiceSession = voiceSession;
    }

    public void writeAndFlush(String message, VdtsSysDB vdtsSysDB) {
        saveOutgoingMessage(message, vdtsSysDB);
        String talkmanMessage = "\"" + message + "\"\r\n\n";
        LOG.info("Ougoing message: [{}]", talkmanMessage);
        try {
            ChannelFuture channelFuture = ctx.writeAndFlush(talkmanMessage);
            LOG.info("Waiting for write.");
            channelFuture.addListener(future -> {
                if (future.isSuccess()) LOG.info("Write succeeded.");
                else {
                    LOG.error("Write failed. {}", future.cause());
                }
                LOG.info("Message sent.");
                ctx.close();
            });
        } catch (Exception e) {
            LOG.error("Error writing talkman output.", e);
        }
    }
}

我的通灵之手是背景。writeAndFlush（字符串消息）失败，原因是

java.lang.UnsupportedOperationException: unsupported message type: String (expected: ByteBuf, FileRegion)

正如我所理解的文档和示例，WriteAndFlush应该向管道写入一个字符串，并且字符串编码器应该在将该字符串转发到套接字进行传输之前将其更改为字节。我已经检查了通道管道，StringEncoder肯定是在那里注册的。我尝试过通过Netty库遵循执行路径，但这种方式是疯狂的。我是否使用了错误的写入呼叫？写和冲洗是否跳过StringEncoder？我应该放弃编程，回去做碰撞测试假人吗？

Answer 1

我想你应该使用频道。writeAndFlush以确保您走完整个通道管道。您最有可能使用ChannelHandlerContext的ChannelHandler，它位于StringEncoder之前，因此不会被它处理。