Netty 对象回显示例服务器 channelRead 方法不适用于我的自定义对象

Question

我最近开始尝试使用 Netty 来创建视频游戏 server/client 关系。我正在使用 Netty 4.1.X 源提供的 Netty "Object Echo" 示例。客户端和服务器包含在不同的项目中。 class "VersionInfo" 在服务器和客户端项目中均可用，但包名称不同。

我遇到的问题是，当我将自定义对象从客户端发送到服务器时，没有收到。但是，如果我发送一个 String 对象，它会完美地工作。

服务器：

    public class Server {
    private int port;

    public Server(int port) {
        this.port = port;
    }

    public void run() throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();

            serverBootstrap.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ServerChannelInitializer())
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .childOption(ChannelOption.SO_KEEPALIVE, true);

            // Bind and start to accept incoming connections.
            ChannelFuture channelFuture = serverBootstrap.bind(port).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.
            channelFuture.channel().closeFuture().sync();
        } finally {
            workerGroup.shutdownGracefully();
            bossGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) {
        try {
            new Server(1337).run();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

服务器通道初始化程序：

    public class ServerChannelInitializer extends ChannelInitializer<SocketChannel> {

    public void initChannel(SocketChannel channel) throws Exception {
        ChannelPipeline pipeline = channel.pipeline();

        pipeline.addLast(new ObjectEncoder());
        pipeline.addLast(new ObjectDecoder(ClassResolvers.cacheDisabled(null)));
        pipeline.addLast(new ObjectEchoServerHandler());
    }
}

对象回显服务器处理程序：

public class ObjectEchoServerHandler extends ChannelInboundHandlerAdapter {

    public static final String VERSION = "1.0.0";

    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        System.out.println("[Server] Channel Active");
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        // business logic here.
        System.out.println("[Server] channelRead()");

        if (msg instanceof VersionInfo) {
            VersionInfo versionInfo = (VersionInfo) msg;
            String clientVersion = versionInfo.version;
            System.out.println("[Server] Version Info Received! Client Version: " + clientVersion + " Local Version: " + VERSION);

            if (clientVersion.equals(VERSION)) {
                VersionInfo success = new VersionInfo();
                success.versionChecked = true;
                ctx.write(success);
                System.out.println("[Server] Version Check Passed!");

            } else {
                // send client version info with false boolean, meaning server version not the same.
                ctx.write(msg);
                System.out.println("[Server] Version Check Failed!");

            }
        } else if (msg instanceof String) {
            ctx.write("[Server] " + msg);
        } else {
            System.out.println("ERROR! Received unknown object! Class name: " + msg.getClass().getSimpleName());
        }
        //ctx.write(msg);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) {
        ctx.flush();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        System.out.println("ExceptionCaught");
        cause.printStackTrace();
        ctx.close();
    }
}

VersionInfo Class（在客户端和服务器上，但包名称不同）：

public class VersionInfo {
    public String version = "1.0.0";
    public boolean versionChecked = false;
}

现在进入客户端代码：

public class Client {
    public static void main(String[] args) throws Exception {

        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(workerGroup);
            bootstrap.channel(NioSocketChannel.class);
            bootstrap.option(ChannelOption.TCP_NODELAY, true);
            bootstrap.option(ChannelOption.SO_KEEPALIVE, true);
            bootstrap.handler(new ClientChannelInitializer());

            // Start the client.
            ChannelFuture channelFuture = bootstrap.connect("localhost", 1337).sync(); // (5)

            // Wait until the connection is closed.
            channelFuture.channel().closeFuture().sync();
        } finally {
            workerGroup.shutdownGracefully();
        }
    }
}

ClientChannelInitializer:

public class ClientChannelInitializer extends ChannelInitializer<SocketChannel> {
    @Override
    public void initChannel(SocketChannel channel) throws Exception {
        ChannelPipeline pipeline = channel.pipeline();

        pipeline.addLast(new ObjectEncoder());
        pipeline.addLast(new ObjectDecoder(ClassResolvers.cacheDisabled(null)));
        pipeline.addLast(new ObjectEchoClientHandler());
    }
}

最后是 ObjectEchoClientHandler：

public class ObjectEchoClientHandler extends ChannelInboundHandlerAdapter {

    private final String string = "This is a test message! :)";
    private final VersionInfo versionInfo = new VersionInfo();


    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        // Send the first message if this handler is a client-side handler.
        System.out.println("[Client] Sending Version Info");
        ctx.writeAndFlush(versionInfo); // this.. does nothing?
        //ctx.writeAndFlush(string); // this works
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        System.out.println("[Client] channelRead()");

        // Check client version
        if (msg instanceof VersionInfo) {
            VersionInfo versionInfo = (VersionInfo) msg;
            System.out.println("[Client] Received Version Info");

            if (versionInfo.versionChecked) {
                System.out.println("[Client] Version Check Passed!");
            } else {
                ctx.close(); // try closing the connection
                System.out.println("[Client] Version Check Failed!");
            }
        } else if (msg instanceof String) {

            System.out.println(msg.toString());

            // Echo back the received object to the server.
            ctx.write(string);
        } else {
            System.out.println("ERROR! Received unknown object! Class name: " + msg.getClass().getSimpleName());
        }
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) {
        ctx.flush();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}

在 ObjectEchoClientHandler channelActive 方法中发送字符串效果很好。发送自定义 POJO/Object 不会调用 ObjectEchoServerHandler channelRead 方法。

可能是什么原因造成的？

编辑 #1: 按照 Nicholas 的建议在下方添加日志文本。抱歉，围绕日志记录调试的块引用。如果没有它，Stack Overflow 编辑器不会让我提交它。

VersionInfo class 更改为反映相同的包名称。新 class:

package com.nettytest.iocommon;

public class VersionInfo {
    public String version = "1.0.0";
    public boolean versionChecked = false;
}

发送自定义 Pojo 后的客户端输出。

Mar 22, 2017 1:09:43 PM io.netty.handler.logging.LoggingHandler channelRegistered SEVERE: [id: 0x237af0b8] REGISTERED Mar 22, 2017 1:09:43 PM io.netty.handler.logging.LoggingHandler connect SEVERE: [id: 0x237af0b8] CONNECT: localhost/127.0.0.1:1337 [Client] Sending Version Info Mar 22, 2017 1:09:43 PM io.netty.handler.logging.LoggingHandler channelActive SEVERE: [id: 0x237af0b8, L:/127.0.0.1:52830 - R:localhost/127.0.0.1:1337] ACTIVE
Mar 22, 2017 1:09:43 PM io.netty.handler.logging.LoggingHandler write SEVERE: [id: 0x237af0b8, L:/127.0.0.1:52830 - R:localhost/127.0.0.1:1337] WRITE: com.nettytest.iocommon.VersionInfo@7544bac Mar 22, 2017 1:09:43 PM io.netty.handler.logging.LoggingHandler flush SEVERE: [id: 0x237af0b8, L:/127.0.0.1:52830 - R:localhost/127.0.0.1:1337] FLUSH

收到自定义 Pojo 后服务器输出。

Mar 22, 2017 1:09:43 PM io.netty.handler.logging.LoggingHandler channelRegistered [Server] Channel Active SEVERE: [id: 0xcdffaece, L:/127.0.0.1:1337 - R:/127.0.0.1:52830] REGISTERED Mar 22, 2017 1:09:43 PM io.netty.handler.logging.LoggingHandler channelActive
SEVERE: [id: 0xcdffaece, L:/127.0.0.1:1337 - R:/127.0.0.1:52830] ACTIVE

Answer 1

调试此问题的一种方法是将 LoggingHandler 添加到您的服务器管道。像这样：

import io.netty.handler.logging.LoggingHandler;
import io.netty.handler.logging.LogLevel;
....
final LoggingHandler loggingHandler = new LoggingHandler(getClass(), 
LogLevel.ERROR);
....
pipeline.addLast(new ObjectDecoder(ClassResolvers.cacheDisabled(null)));
pipeline.addLast("logger", loggingHandler);
pipeline.addLast(new ObjectEchoServerHandler());
....

我最初的怀疑是，由于您传递的 pojo 类型在客户端和服务器上具有不同的包名称（意味着它们不相同 class），因此客户端上的 ObjectDecoder 失败了，因为它在其 class 路径中找不到 class。为了使其正常工作，class 必须存在于服务器和客户端 class 路径中。

Netty 对象回显示例服务器 channelRead 方法不适用于我的自定义对象

Netty object echo example server channelRead method not working with my custom objects

java

object

pojo

echo

netty