前面使用netty实现了http服务器，已经可以从浏览器进行访问，其实netty也可以实现http客户端，来访问netty实现的http服务器

一、httpclient

public class HttpClient {
    public void connect(String host, int port) throws Exception {
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(workerGroup);
            b.channel(NioSocketChannel.class);
            b.option(ChannelOption.SO_KEEPALIVE, true);
            b.handler(new ChannelInitializer<SocketChannel>() {
                @Override
                public void initChannel(SocketChannel ch) throws Exception {
                    // 客户端接收到的是httpResponse响应，所以要使用HttpResponseDecoder进行解码
                    ch.pipeline().addLast(new HttpResponseDecoder());
                    // 客户端发送的是httpRequest，所以要使用HttpRequestEncoder进行编码
                    ch.pipeline().addLast(new HttpRequestEncoder());
                    ch.pipeline().addLast(new HttpClientHandler());
                }
            });
            ChannelFuture f = b.connect(host, port).sync();
            URI uri = new URI("/test");
            String msg = "Are you ok?";
            DefaultFullHttpRequest request = new DefaultFullHttpRequest(
                    HttpVersion.HTTP_1_1, HttpMethod.POST, uri.toASCIIString(),
                    Unpooled.wrappedBuffer(msg.getBytes()));
            // 构建http请求
            request.headers().set(HttpHeaderNames.HOST, host);
            request.headers().set(HttpHeaderNames.CONNECTION,
                    HttpHeaderNames.CONNECTION);
            request.headers().set(HttpHeaderNames.CONTENT_LENGTH,
                    request.content().readableBytes());
            request.headers().set("messageType", "normal");
            request.headers().set("businessType", "testServerState");
            // 发送http请求
            f.channel().write(request);
            f.channel().flush();
            f.channel().closeFuture().sync();
        } finally {
            workerGroup.shutdownGracefully();
        }
    }
    public static void main(String[] args) throws Exception {
        HttpClient client = new HttpClient();
        client.connect("127.0.0.1", 8000);
    }
}

二、HttpClientHandler

public class HttpClientHandler extends ChannelInboundHandlerAdapter {
    private ByteBufToBytes reader;
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg)
            throws Exception {
        if (msg instanceof HttpResponse) {
            HttpResponse response = (HttpResponse) msg;
            System.out.println("CONTENT_TYPE:"+ response.headers().get(HttpHeaderNames.CONTENT_TYPE));
            if (HttpUtil.isContentLengthSet(response)) {
                reader = new ByteBufToBytes(
                        (int) HttpUtil.getContentLength(response));
            }
        }
        if (msg instanceof HttpContent) {
            HttpContent httpContent = (HttpContent) msg;
            ByteBuf content = httpContent.content();
            System.out.println(content);
            System.out.println(reader);
            reader.reading(content);
            content.release();
            if (reader.isEnd()) {
                String resultStr = new String(reader.readFull());
                System.out.println("Server said:" + resultStr);
                ctx.close();
            }
        }
    }

}

三、工具类

public class ByteBufToBytes {
    private ByteBuf temp;
    private boolean end = true;
    public ByteBufToBytes(int length) {
        temp = Unpooled.buffer(length);
    }
    public void reading(ByteBuf datas) {
        datas.readBytes(temp, datas.readableBytes());
        if (this.temp.writableBytes() != 0) {
            end = false;
        } else {
            end = true;
        }
    }
    public boolean isEnd() {
        return end;
    }
    public byte[] readFull() {
        if (end) {
            byte[] contentByte = new byte[this.temp.readableBytes()];
            this.temp.readBytes(contentByte);
            this.temp.release();
            return contentByte;
        } else {
            return null;
        }
    }
    public byte[] read(ByteBuf datas) {
        byte[] bytes = new byte[datas.readableBytes()];
        datas.readBytes(bytes);
        return bytes;
    }
}

 转自：https://blog.csdn.net/wangshuang1631/article/details/73251180/