JAVA写HTTP代理服务器(二)-netty实现

接上一篇,因为是用BIO的一个连接一个线程去处理，对于HTTP这种短连接协议来说CPU开销是非常大的，就算加入了线程池也不能完美解决BIO的缺陷，所以可以用NIO进行服务器的优化，NIO基于IO多路复用以实现单线程处理大量连接,但是编写起来比较复杂，所以就选择了netty，这里就不在多叙netty是什么了。

思路

netty有内置的http编解码器，那就可以轻易做到不只是转发原始数据，而是可以修改响应内容，当然仅限http代理，因为https代理的话私钥都存在客户端和目标服务器上，代理服务器只能捕获到双方的公钥，无法解密成明文，除非代理服务器制作证书,并实现SSL/TLS握手。

实现

EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup(2);
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 100)
                    .option(ChannelOption.TCP_NODELAY, true)
                    .handler(new LoggingHandler(LogLevel.INFO))
                    .childHandler(new ChannelInitializer<Channel>() {

                        @Override
                        protected void initChannel(Channel ch) throws Exception {
                            ch.pipeline().addLast("httpCodec",new HttpServerCodec());
                            ch.pipeline().addLast("httpObject",new HttpObjectAggregator(65536));
                            ch.pipeline().addLast("serverHandle",new HttpProxyServerHandle());
                        }
                    });
            ChannelFuture f = b
                    .bind(port)
                    .sync();
            f.channel().closeFuture().sync();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }

public class HttpProxyServerHandle extends ChannelInboundHandlerAdapter {

    private ChannelFuture cf;
    private String host;
    private int port;

    @Override
    public void channelRead(final ChannelHandlerContext ctx, final Object msg) throws Exception {
        if (msg instanceof FullHttpRequest) {
            FullHttpRequest request = (FullHttpRequest) msg;
            String host = request.headers().get("host");
            String[] temp = host.split(":");
            int port = 80;
            if (temp.length > 1) {
                port = Integer.parseInt(temp[1]);
            } else {
                if (request.uri().indexOf("https") == 0) {
                    port = 443;
                }
            }
            this.host = temp[0];
            this.port = port;
            if ("CONNECT".equalsIgnoreCase(request.method().name())) {//HTTPS建立代理握手
                HttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, NettyHttpProxyServer.SUCCESS);
                ctx.writeAndFlush(response);
                ctx.pipeline().remove("httpCodec");
                ctx.pipeline().remove("httpObject");
                return;
            }
            //连接至目标服务器
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(ctx.channel().eventLoop()) // 注册线程池
                    .channel(ctx.channel().getClass()) // 使用NioSocketChannel来作为连接用的channel类
                    .handler(new HttpProxyInitializer(ctx.channel()));

            ChannelFuture cf = bootstrap.connect(temp[0], port);
            cf.addListener(new ChannelFutureListener() {
                public void operationComplete(ChannelFuture future) throws Exception {
                    if (future.isSuccess()) {
                        future.channel().writeAndFlush(msg);
                    } else {
                        ctx.channel().close();
                    }
                }
            });
//            ChannelFuture cf = bootstrap.connect(temp[0], port).sync();
//            cf.channel().writeAndFlush(request);
        } else { // https 只转发数据，不做处理
            if (cf == null) {
                //连接至目标服务器
                Bootstrap bootstrap = new Bootstrap();
                bootstrap.group(ctx.channel().eventLoop()) // 复用客户端连接线程池
                        .channel(ctx.channel().getClass()) // 使用NioSocketChannel来作为连接用的channel类
                        .handler(new ChannelInitializer() {

                            @Override
                            protected void initChannel(Channel ch) throws Exception {
                                ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
                                    @Override
                                    public void channelRead(ChannelHandlerContext ctx0, Object msg) throws Exception {
                                        ctx.channel().writeAndFlush(msg);
                                    }
                                });
                            }
                        });
                cf = bootstrap.connect(host, port);
                cf.addListener(new ChannelFutureListener() {
                    public void operationComplete(ChannelFuture future) throws Exception {
                        if (future.isSuccess()) {
                            future.channel().writeAndFlush(msg);
                        } else {
                            ctx.channel().close();
                        }
                    }
                });
            } else {
                cf.channel().writeAndFlush(msg);
            }
        }
    }


}

public class HttpProxyInitializer extends ChannelInitializer{

    private Channel clientChannel;

    public HttpProxyInitializer(Channel clientChannel) {
        this.clientChannel = clientChannel;
    }

    @Override
    protected void initChannel(Channel ch) throws Exception {
        ch.pipeline().addLast(new HttpClientCodec());
        ch.pipeline().addLast(new HttpObjectAggregator(6553600));
        ch.pipeline().addLast(new HttpProxyClientHandle(clientChannel));
    }
}

public class HttpProxyClientHandle extends ChannelInboundHandlerAdapter {

    private Channel clientChannel;

    public HttpProxyClientHandle(Channel clientChannel) {
        this.clientChannel = clientChannel;
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        FullHttpResponse response = (FullHttpResponse) msg;
        //修改http响应体返回至客户端
        response.headers().add("test","from proxy");
        clientChannel.writeAndFlush(msg);
    }
}

后记

netty框架下开发简单的高性能http代理服务器，并且用内置的http编解码器实现了响应体的修改。后续会再深入HTTPS明文捕获，由代理服务器制作CA证书，并实现与目标服务器SSL/TLS握手。
代码托管在github上，欢迎start