netty系列之:小白福利！手把手教你做一个简单的代理服务器

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":1},"content":[{"type":"text","text":"简介","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"爱因斯坦说过:所有的伟大，都产生于简单的细节中。netty为我们提供了如此强大的eventloop、channel通过对这些简单东西的有效利用，可以得到非常强大的应用程序，比如今天要讲的代理。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":1},"content":[{"type":"text","text":"代理和反向代理","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"相信只要是程序员应该都听过nginx服务器了，这个超级优秀nginx一个很重要的功能就是做反向代理。那么有小伙伴要问了，有反向代理肯定就有正向代理，那么他们两个有什么区别呢？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"先讲一下正向代理，举个例子，最近流量明星备受打击，虽然被打压，但是明星就是明星，一般人是见不到的，如果有人需要跟明星对话的话，需要首先经过明星的经纪人，有经纪人将话转达给明星。这个经纪人就是正向代理。我们通过正向代理来访问要访问的对象。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"那么什么是反向代理呢？比如现在出现了很多人工智能，假如我们跟智能机器人A对话，然后A把我们之间的对话转给了后面的藏着的人，这个人用他的智慧，回答了我们的对话，交由智能机器人A输出，最终实现了人工智能。这个过程就叫做反向代理。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":1},"content":[{"type":"text","text":"netty实现代理的原理","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"那么在netty中怎么实现这个代理服务器呢？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"首选我们首先代理服务器是一个服务器，所以我们需要在netty中使用ServerBootstrap创建一个服务器：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"text"},"content":[{"type":"text","text":"EventLoopGroup bossGroup = new NioEventLoopGroup(1);\n EventLoopGroup workerGroup = new NioEventLoopGroup();\n try {\n ServerBootstrap b = new ServerBootstrap();\n b.group(bossGroup, workerGroup)\n .channel(NioServerSocketChannel.class)\n .handler(new LoggingHandler(LogLevel.INFO))\n .childHandler(new SimpleDumpProxyInitializer(REMOTE_HOST, REMOTE_PORT))\n .childOption(ChannelOption.AUTO_READ, false)\n .bind(LOCAL_PORT).sync().channel().closeFuture().sync();\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在这个local服务器中，我们传入ProxyInitializer。在这个handler初始化器中，我们传入自定义的handler：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"text"},"content":[{"type":"text","text":" public void initChannel(SocketChannel ch) {\n ch.pipeline().addLast(\n new LoggingHandler(LogLevel.INFO),\n new SimpleDumpProxyInboundHandler(remoteHost, remotePort));\n }\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在自定义的handler中，我们使用Bootstrap创建一个client，用来连接远程要代理的服务器，我们将这个client端的创建放在channelActive方法中：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"text"},"content":[{"type":"text","text":"// 开启outbound连接\n Bootstrap b = new Bootstrap();\n b.group(inboundChannel.eventLoop())\n .channel(ctx.channel().getClass())\n .handler(new SimpleDumpProxyOutboundHandler(inboundChannel))\n .option(ChannelOption.AUTO_READ, false);\n ChannelFuture f = b.connect(remoteHost, remotePort);\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"然后在client建立好连接之后，就可以从inboundChannel中读取数据了：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"text"},"content":[{"type":"text","text":"outboundChannel = f.channel();\n f.addListener(future -> {\n if (future.isSuccess()) {\n // 连接建立完毕，读取inbound数据\n inboundChannel.read();\n } else {\n // 关闭inbound channel\n inboundChannel.close();\n }\n });\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"因为是代理服务，所以需要将inboundChannel读取的数据，转发给outboundChannel，所以在channelRead中我们需要这样写：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"text"},"content":[{"type":"text","text":" public void channelRead(final ChannelHandlerContext ctx, Object msg) {\n // 将inboundChannel中的消息读取，并写入到outboundChannel\n if (outboundChannel.isActive()) {\n outboundChannel.writeAndFlush(msg).addListener((ChannelFutureListener) future -> {\n if (future.isSuccess()) {\n // flush成功，读取下一个消息\n ctx.channel().read();\n } else {\n future.channel().close();\n }\n });\n }\n }\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"当outboundChannel写成功之后，再继续inboundChannel的读取工作。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"同样对于client的outboundChannel来说，也有一个handler，在这个handler中，我们需要将outboundChannel读取到的数据反写会inboundChannel中：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"text"},"content":[{"type":"text","text":" public void channelRead(final ChannelHandlerContext ctx, Object msg) {\n // 将outboundChannel中的消息读取，并写入到inboundChannel中\n inboundChannel.writeAndFlush(msg).addListener((ChannelFutureListener) future -> {\n if (future.isSuccess()) {\n ctx.channel().read();\n } else {\n future.channel().close();\n }\n });\n }\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"当inboundChannel写成功之后，再继续outboundChannel的读取工作。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如此一个简单的代理服务器就完成了。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":1},"content":[{"type":"text","text":"实战","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果我们将本地的8000端口，代理到www.163.com的80端口，会发生什么情况呢？运行我们的程序，访问http://localhost:8000, 我们会看到下面的页面：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/a9/a9a954e6c723151b6c0bc931a1fd27d6.png","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"为什么没有如我们想象的那样展示正常的页面呢？那是因为我们代理过去之后的域名是localhost，而不是正常的www.163.com, 所以服务器端不认识我们的请求，从而报错。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":1},"content":[{"type":"text","text":"总结","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"本文的代理服务器之间简单的转发请求，并不能够处理上述的场景，那么该怎么解决上面的问题呢？ 敬请期待我的后续文章！","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"本文的例子可以参考：","attrs":{}},{"type":"link","attrs":{"href":"https://github.com/ddean2009/learn-netty4","title":"","type":null},"content":[{"type":"text","text":"learn-netty4","attrs":{}}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"本文已收录于 ","attrs":{}},{"type":"link","attrs":{"href":"http://www.flydean.com/35-netty-simple-proxy/","title":"","type":null},"content":[{"type":"text","text":"http://www.flydean.com/35-netty-simple-proxy/","attrs":{}}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最通俗的解读，最深刻的干货，最简洁的教程，众多你不知道的小技巧等你来发现！","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"欢迎关注我的公众号:「程序那些事」,懂技术，更懂你！","attrs":{}}]}],"attrs":{}}]}