Netty是如何解析Redis的RESP协议—响应篇

public class RedisDecoderTest {
    public static void main(String[] args) {
         EmbeddedChannel channel = newChannel(false);


        System.out.println(channel.writeInbound(byteBufOf("$6\r\nfoobar\r")));
        System.out.println(channel.writeInbound(byteBufOf("\n")));


        RedisMessage msg = channel.readInbound();
        System.out.println(msg instanceof FullBulkStringRedisMessage);

        String bytes = stringOf(((FullBulkStringRedisMessage) msg).content());
        System.out.println(bytes);


        ReferenceCountUtil.release(msg);

        channel.finish();
    }
    private static EmbeddedChannel newChannel(boolean decodeInlineCommands) {
        return new EmbeddedChannel(
                new RedisDecoder(decodeInlineCommands),
                new RedisBulkStringAggregator(),
                new RedisArrayAggregator());
    }
}

$<length>\r\n<data>\r\n
比如
$5\r\nhello\r\n
$0\r\n\r\n

System.out.println(channel.writeInbound(byteBufOf("$6\r\nfoobar\r")));
 System.out.println(channel.writeInbound(byteBufOf("\n")));

/**
 * Simple Redis client that demonstrates Redis commands against a Redis server.
 */
public class RedisClient {
    private static final String HOST = System.getProperty("host", "192.168.200.128");
    private static final int PORT = Integer.parseInt(System.getProperty("port", "6379"));

    public static void main(String[] args) throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group)
             .channel(NioSocketChannel.class)
             .handler(new ChannelInitializer<SocketChannel>() {
                 @Override
                 protected void initChannel(SocketChannel ch) throws Exception {
                     ChannelPipeline p = ch.pipeline();
                     p.addLast(new RedisDecoder());
                     p.addLast(new RedisBulkStringAggregator());
                     p.addLast(new RedisArrayAggregator());
                     p.addLast(new RedisEncoder());
                     p.addLast(new RedisClientHandler());
                 }
             });

            // Start the connection attempt.
            Channel ch = b.connect(HOST, PORT).sync().channel();

            // Read commands from the stdin.
            System.out.println("Enter Redis commands (quit to end)");
            ChannelFuture lastWriteFuture = null;
            BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
            for (;;) {
                final String input = in.readLine();
                final String line = input != null ? input.trim() : null;
                if (line == null || "quit".equalsIgnoreCase(line)) { // EOF or "quit"
                    ch.close().sync();
                    break;
                } else if (line.isEmpty()) { // skip `enter` or `enter` with spaces.
                    continue;
                }
                // Sends the received line to the server.
                lastWriteFuture = ch.writeAndFlush(line);
                lastWriteFuture.addListener(new GenericFutureListener<ChannelFuture>() {
                    @Override
                    public void operationComplete(ChannelFuture future) throws Exception {
                        if (!future.isSuccess()) {
                            System.err.print("write failed: ");
                            future.cause().printStackTrace(System.err);
                        }
                    }
                });
            }

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


/**
 * An example Redis client handler. This handler read input from STDIN and write output to STDOUT.
 */
public class RedisClientHandler extends ChannelDuplexHandler {

    @Override
    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
        String[] commands = ((String) msg).split("\\s+");
        List<RedisMessage> children = new ArrayList<RedisMessage>(commands.length);
        for (String cmdString : commands) {
            children.add(new FullBulkStringRedisMessage(ByteBufUtil.writeUtf8(ctx.alloc(), cmdString)));
        }
        RedisMessage request = new ArrayRedisMessage(children);
        ctx.write(request, promise);
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        RedisMessage redisMessage = (RedisMessage) msg;
        printAggregatedRedisResponse(redisMessage);
        ReferenceCountUtil.release(redisMessage);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        System.err.print("exceptionCaught: ");
        cause.printStackTrace(System.err);
        ctx.close();
    }

    private static void printAggregatedRedisResponse(RedisMessage msg) {
        if (msg instanceof SimpleStringRedisMessage) {
            System.out.println(((SimpleStringRedisMessage) msg).content());
        } else if (msg instanceof ErrorRedisMessage) {
            System.out.println(((ErrorRedisMessage) msg).content());
        } else if (msg instanceof IntegerRedisMessage) {
            System.out.println(((IntegerRedisMessage) msg).value());
        } else if (msg instanceof FullBulkStringRedisMessage) {
            System.out.println(getString((FullBulkStringRedisMessage) msg));
        } else if (msg instanceof ArrayRedisMessage) {
            for (RedisMessage child : ((ArrayRedisMessage) msg).children()) {
                printAggregatedRedisResponse(child);
            }
        } else {
            throw new CodecException("unknown message type: " + msg);
        }
    }

    private static String getString(FullBulkStringRedisMessage msg) {
        if (msg.isNull()) {
            return "(null)";
        }
        return msg.content().toString(CharsetUtil.UTF_8);
    }
}