先来完成一个最简单的httprequest和httpresponse的实现。

客户端

NioEventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(workerGroup)
                    .channel(NioSocketChannel.class)
                    .option(ChannelOption.SO_KEEPALIVE, true)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
                            socketChannel.pipeline().addLast(new HttpRequestEncoder());//客户端对发送的httpRequest进行编码
                            socketChannel.pipeline().addLast(new HttpResponseDecoder());//客户端需要对服务端返回的httpresopnse解码
                            // socketChannel.pipeline().addLast(new HttpClientCodec());//HttpClientCodec()包含了上面两种
                            socketChannel.pipeline().addLast(new HttpClientDealing());
                        }
                    });

            Channel channel = bootstrap.connect("127.0.0.1", 8080).sync().channel();

            URI uri = new URI("http://127.0.0.1:8080");
            DefaultFullHttpRequest httpRequest = new DefaultFullHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.GET, uri.toASCIIString(), Unpooled.wrappedBuffer(msg.getBytes("UTF-8")));//生成一个默认的httpRequest。

            httpRequest.headers().set(HttpHeaders.Names.HOST, "127.0.0.1");
            httpRequest.headers().set(HttpHeaders.Names.CONNECTION, HttpHeaders.Values.KEEP_ALIVE);
            httpRequest.headers().set(HttpHeaders.Names.CONTENT_LENGTH, httpRequest.content().readableBytes());//可以在httpRequest.headers中设置各种需要的信息。

            channel.writeAndFlush(httpRequest).sync();//发送

            channel.closeFuture().sync();

        } finally {
            workerGroup.shutdownGracefully();
        }
    }

    private static class HttpClientDealing extends ChannelInboundHandlerAdapter {
        @Override
        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
            if(msg instanceof HttpResponse){
                System.out.println(msg.toString());//打印服务器返回的httpResponse
            }

            if(msg instanceof HttpContent) {
                System.out.println(msg.toString());
            }
        }
    }

服务端

NioEventLoopGroup bossGroup = new NioEventLoopGroup();
        NioEventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .handler(new LoggingHandler(LogLevel.INFO))
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
                         //   socketChannel.pipeline().addLast(new HttpServerCodec());
                            socketChannel.pipeline().addLast(new HttpRequestDecoder());//服务器添加httpRequest解码
                            socketChannel.pipeline().addLast(new HttpResponseEncoder());//服务器添加httpResponse编码
                            socketChannel.pipeline().addLast(new HttpServerDataDealing());
                        }
                    });

            Channel channel = serverBootstrap.bind(8080).sync().channel();

            channel.closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    private static class HttpServerDataDealing extends ChannelInboundHandlerAdapter {
        @Override
        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
            if(msg instanceof HttpRequest)
            {
                System.out.println(msg.toString());//打印httpRequest
            }

            if(msg instanceof HttpContent)
            {
                System.out.println(msg.toString());
            }

            HttpResponse httpResponse = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, Unpooled.wrappedBuffer("hello client".getBytes()));//建立httpResponse
            httpResponse.headers().add(HttpHeaders.Names.CONTENT_TYPE, "text/plain");
            httpResponse.headers().add(HttpHeaders.Names.CONTENT_LENGTH, 11);

            ctx.writeAndFlush(httpResponse);//返回响应的httpResponse
        }
    }

如果只是发送简单的http请求以及响应，其实非常简单。但是为了完成功能开发，一般会在http头中加入一定的消息列表用于表示此次请求的一些参数

名称	作用
Accept	用于制定客户端接收哪些类型的信息
Accept-Charset	用于指定客户端接受的字符集
Accept-Encoding	类似于Accept，但是它用于指定一种自然语言
Authorization	主要用于证明客户端有权查看某个资源。当浏览器访问一个页面时，如果收到服务器的响应代码为401（未授权），可以发送一个包含Authorization请求报头域的请求，要求服务器对其进行认证
Host	发送请求时，该报头域是必需的，用于指定被请求的资源的Internet主机和端口号，它通常是从HTTP URL中提取出来的
User-Agent	允许客户端将它的操作系统，浏览器和其他属性告诉服务器
Content-Length	请求消息体的长度
Content-Type	表示后面的文档属于什么MIME类型。Servlet默认为text/plain，但通常需要显式的指定为text/html。由于经常要设置Content-Type，因此HttpServletResponse提供了一个专用的方法setContentType
Connection	连接类型

get方法和post方法的区别

根据名称即可得知，这两种方法在设计的时候get就是为了获取资源，而post是为了发送资源
在自己机子上随便抓了一个http的get请求如下：

get方法

这里包含了get请求协议和Cookie的信息。但是没有body，Post包没想到怎么抓就没有示例了。其实get和post在内容上的区别就是post多了一个body，即在httpheaders下面还有一段内容，用于保存http提交的信息。表现在netty代码上如下所示

get方法

        HttpRequest request = new DefaultHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.GET, uriGet.toASCIIString());
        HttpHeaders headers = request.headers();
        headers.set(HttpHeaderNames.HOST, host);
        headers.set(HttpHeaderNames.CONNECTION, HttpHeaderValues.CLOSE);
        headers.set(HttpHeaderNames.ACCEPT_ENCODING, HttpHeaderValues.GZIP + "," + HttpHeaderValues.DEFLATE);

        headers.set(HttpHeaderNames.ACCEPT_CHARSET, "ISO-8859-1,utf-8;q=0.7,*;q=0.7");
        headers.set(HttpHeaderNames.ACCEPT_LANGUAGE, "fr");
        headers.set(HttpHeaderNames.REFERER, uriSimple.toString());
        headers.set(HttpHeaderNames.USER_AGENT, "Netty Simple Http Client side");
        headers.set(HttpHeaderNames.ACCEPT, "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8");

        // send request
        channel.writeAndFlush(request);

post方法

        HttpDataFactory factory = new DefaultHttpDataFactory(DefaultHttpDataFactory.MINSIZE); // Disk if MINSIZE exceed
        // Prepare the HTTP request.
        HttpRequest request = new DefaultHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.POST, uriSimple.toASCIIString());

        // Use the PostBody encoder
        HttpPostRequestEncoder bodyRequestEncoder =
                new HttpPostRequestEncoder(factory, request, false);  // false => not multipart
        //可以给body添加文件等
        bodyRequestEncoder.addBodyFileUpload("myfile", file, "application/x-zip-compressed", false);
        // it is legal to add directly header or cookie into the request until finalize
        //这部分headers和get方法一样
        for (Entry<String, String> entry : headers) {
            request.headers().set(entry.getKey(), entry.getValue());
        }

        // finalize request
        request = bodyRequestEncoder.finalizeRequest();

        // send request
        channel.write(request);

post增加的内容

 HttpDataFactory factory = new DefaultHttpDataFactory(DefaultHttpDataFactory.MINSIZE); 
        HttpPostRequestEncoder bodyRequestEncoder =
                new HttpPostRequestEncoder(factory, request, false);  // false => not multipart
 bodyRequestEncoder.addBodyFileUpload("myfile", file, "application/x-zip-compressed", false);
  request = bodyRequestEncoder.finalizeRequest();

post方法利用HttpPostRequestEncoder编码body信息，然后加入到post消息中进行发送。