Question

我正在开发一个应用服务器，其中一部分将基于Netty 4.0。但是，我遇到了频道共享变量的问题我已经读过在我需要使用的其他上下文处理程序中使用这些变量

context.channel（）。ATTR（键）.SET（）

而不仅仅是

context.attr（键）.SET（）

将我的变量附加到当前频道。
像这里：

 public class HadlePackets extends ChannelInboundHandlerAdapter {

private static final Logger LOG = LoggerFactory.getLogger(HadlePackets.class);
public AttributeKey<Integer> clientIDattrKey = new AttributeKey<Integer>  ("ClientID");

@Override
public void channelRead(ChannelHandlerContext ctx, Object message) throws Exception {
 ...
ctx.channel().attr(clientIDattrKey).set(IDnum); //bind ID to channel

...
}
}

但是，如何在处理程序的另一个上下文中检索变量的值？仍然需要属性键，我无法从附加变量的处理程序中获取它。

public class StorageHandler extends ChannelInboundHandlerAdapter{
private static final Logger LOG = LoggerFactory.getLogger(StorageSaveHandler.class);

@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
    Integer clientID = (Integer)ctx.channel().attr(null).get(); //How can i get proper key for this channel attribute?
    ctx.fireChannelInactive();

}

Answer 1

这应该有效，因为它是public static：

@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
    Integer clientID = (Integer) ctx.channel().attr(HandlePackets.clientIDattrKey).get();
    ctx.fireChannelInactive();
}

以下是我如何使用它的一个小例子。这只是一段代码摘录：

public class NettyServer implements Runnable {
final static AttributeKey<Long> CHECKSUMKEY = AttributeKey.valueOf("calcchecksum");
final static AttributeKey<Command> COMMANDKEY = AttributeKey.valueOf("command");
final static AttributeKey<Long> FILEHANDLEKEY = AttributeKey.valueOf("filehandle");
final static AttributeKey<File> PATHKEY = AttributeKey.valueOf("destpath");
final static AttributeKey<FileOutputStream> OUTPUTSTREAM = AttributeKey.valueOf("stream");

@Override
public void run() {
    try {
        EventLoopGroup bossGroup = new NioEventLoopGroup(BOSS_THREADS);
        EventLoopGroup workerGroup = new NioEventLoopGroup(calculateThreadCount());
        try {
            ServerBootstrap bootstrap = new ServerBootstrap();

            // This option will allow binding to an already bound ip:port
            // combination.
            // This is usually used to be able to restart a server if it
            // crashed/got killed
            // (so while the socket is still in the TIME_WAIT state).
            bootstrap.option(ChannelOption.SO_REUSEADDR, true);
            bootstrap.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class).childHandler(new ChannelInitializer<SocketChannel>() {
                @Override
                public void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast("ObjectDecoder", new ObjectDecoder(ClassResolvers.cacheDisabled(null)));
                    ch.pipeline().addLast("ObjectEncoder", new ObjectEncoder());
                    ch.pipeline().addLast("CommandHandler", new ServerCommandHandler(server, logger));
                    ch.pipeline().addLast("FileHandler", new ServerFileHandler(server, logger));
                    ch.pipeline().addLast("ChecksumHandler", new ServerChecksumHandler(server, logger));
                }
            });

            try {
                // Bind and start to accept incoming connections.
                bootstrap.bind(port).sync().channel().closeFuture().sync();
            } catch (InterruptedException e) {
                logger.debug(Message.CMDTRANSFER_INTERRUPTED_DEBUG, e.getMessage());
            }
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    } catch (Exception e) {
        logger.error(Message.CMDTRANSFER_CONNECT_ERROR, e.getMessage());
    }
}
}

如您所见，我有几个共享频道属性的处理程序。

public class ServerCommandHandler extends ChannelInboundHandlerAdapter {
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ctx.channel().attr(NettyServer.COMMANDKEY).set(clCommand);
        ctx.fireChannelRead(msg);
    }
}

public class ServerChecksumHandler extends ChannelInboundHandlerAdapter {
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        if ctx.channel().attr(NettyServer.COMMANDKEY).getAndRemove() == referenceCommand {
            //do something
        }
    }
}

在不同的上下文处理程序中使用通道属性

1 个答案: