使用netty处理在线播放mp4请求

可以使用Netty来处理在线播放mp4请求，下面是大致的实现思路：

1. 创建一个Netty服务器，监听指定的端口，等待客户端连接。

2. 当有客户端连接时，创建一个ChannelPipeline，添加一系列的ChannelHandler，用于处理请求和响应。

3. 当收到客户端的请求时，解析请求中的URL，获取要播放的mp4文件的路径。

4. 使用Java的NIO API读取mp4文件，将数据写入响应的Channel中，实现流式传输。

5. 客户端收到响应后，使用HTML5的video标签播放mp4文件，实现在线播放。

示例代码如下：

public class Mp4StreamingServer {

    private final int port;

    public Mp4StreamingServer(int port) {
        this.port = port;
    }

    public void run() throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        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 {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new HttpServerCodec());
                            pipeline.addLast(new HttpObjectAggregator(65536));
                            pipeline.addLast(new ChunkedWriteHandler());
                            pipeline.addLast(new Mp4StreamingServerHandler());
                        }
                    });

            ChannelFuture f = b.bind(port).sync();
            f.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception {
        int port = Integer.parseInt(args[0]);
        new Mp4StreamingServer(port).run();
    }
}

public class Mp4StreamingServerHandler extends SimpleChannelInboundHandler<FullHttpRequest> {

    private static final String CONTENT_TYPE = "Content-Type";
    private static final String CONTENT_LENGTH = "Content-Length";
    private static final String KEEP_ALIVE = "keep-alive";

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {
        if (request.method() != HttpMethod.GET) {
            sendError(ctx, HttpResponseStatus.METHOD_NOT_ALLOWED);
            return;
        }

        String uri = request.uri();
        String path = sanitizeUri(uri);
        if (path == null) {
            sendError(ctx, HttpResponseStatus.FORBIDDEN);
            return;
        }

        File file = new File(path);
        if (!file.exists() || file.isHidden() || !file.isFile()) {
            sendError(ctx, HttpResponseStatus.NOT_FOUND);
            return;
        }

        if (!file.canRead()) {
            sendError(ctx, HttpResponseStatus.FORBIDDEN);
            return;
        }

        RandomAccessFile raf = new RandomAccessFile(file, "r");
        long fileLength = raf.length();

        HttpResponse response = new DefaultHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK);
        HttpUtil.setContentLength(response, fileLength);
        setContentTypeHeader(response, file);
        if (HttpUtil.isKeepAlive(request)) {
            response.headers().set(HttpHeaderNames.CONNECTION, HttpHeaderValues.KEEP_ALIVE);
        }
        ctx.write(response);

        ChannelFuture sendFileFuture = ctx.write(new ChunkedFile(raf, 0, fileLength, 8192), ctx.newProgressivePromise());
        sendFileFuture.addListener(new ChannelProgressiveFutureListener() {
            @Override
            public void operationProgressed(ChannelProgressiveFuture future, long progress, long total) throws Exception {
                if (total < 0) {
                    System.err.println("Transfer progress: " + progress);
                } else {
                    System.err.println("Transfer progress: " + progress + " / " + total);
                }
            }

            @Override
            public void operationComplete(ChannelProgressiveFuture future) throws Exception {
                System.err.println("Transfer complete.");
            }
        });

        ChannelFuture lastContentFuture = ctx.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT);
        if (!HttpUtil.isKeepAlive(request)) {
            lastContentFuture.addListener(ChannelFutureListener.CLOSE);
        }
    }

    private static final Pattern INSECURE_URI = Pattern.compile(".*[<>&\"].*");

    private String sanitizeUri(String uri) {
        try {
            uri = URLDecoder.decode(uri, "UTF-8");
        } catch (UnsupportedEncodingException e) {
            try {
                uri = URLDecoder.decode(uri, "ISO-8859-1");
            } catch (UnsupportedEncodingException e1) {
                throw new Error();
            }
        }

        if (!uri.startsWith("/")) {
            return null;
        }

        uri = uri.replace('/', File.separatorChar);

        if (uri.contains(File.separator + '.') ||
            uri.contains('.' + File.separator) ||
            uri.startsWith(".") || uri.endsWith(".") ||
            INSECURE_URI.matcher(uri).matches()) {
            return null;
        }

        return System.getProperty("user.dir") + File.separator + uri;
    }

    private static void sendError(ChannelHandlerContext ctx, HttpResponseStatus status) {
        FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, status,
                Unpooled.copiedBuffer("Failure: " + status.toString() + "\r\n", CharsetUtil.UTF_8));
        response.headers().set(CONTENT_TYPE, "text/plain; charset=UTF-8");

        ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
    }

    private static void setContentTypeHeader(HttpResponse response, File file) {
        MimetypesFileTypeMap mimeTypesMap = new MimetypesFileTypeMap();
        response.headers().set(CONTENT_TYPE, mimeTypesMap.getContentType(file.getPath()));
    }
}

在上面的示例代码中，Mp4StreamingServer类是启动Netty服务器的入口，它创建了一个ServerBootstrap实例，配置了NioEventLoopGroup、NioServerSocketChannel、ChannelInitializer和Mp4StreamingServerHandler等组件，并监听指定的端口，等待客户端连接。

Mp4StreamingServerHandler类是处理请求和响应的核心，它继承了SimpleChannelInboundHandler<FullHttpRequest>，重写了channelRead0方法，用于读取客户端的请求，解析请求中的URL，获取要播放的mp4文件的路径，读取mp4文件并将数据写入响应的Channel中，实现流式传输。同时，如果客户端请求中包含keep-alive头，则在响应中添加该头，以保持连接，避免浪费资源。最后，通过调用ctx.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT)方法，通知客户端数据传输完成，释放资源。

总之，使用Netty来处理在线播放mp4请求，可以提高服务器的并发处理能力和吞吐量，同时实现实时流媒体传输，提升用户体验。