Netty 替代 Tomcat

**

1. 使用 Netty 作为 web 服务器实例

1**. Netty 作为 web 服务器的流程图**

2. 实现代码

public void start() {
    EventLoopGroup bossGroup = new NioEventLoopGroup();
    EventLoopGroup workerGroup = new NioEventLoopGroup();
    ServerBootstrap bootstrap = new ServerBootstrap();
    try {
        ChannelFuture future = bootstrap
                .group(bossGroup,// bossGroup  负责管理所有的链接    
                 workerGroup) // workerGroup  处理业务
                .channel(NioServerSocketChannel.class)
                //处理 客户端发送的数据
                .childHandler(new MyServerChannelInitializer())
                .bind(8080).sync();// 绑定端口 8080
        future.channel().closeFuture().sync();
    } catch (InterruptedException e) {
        throw new RuntimeException(e);
    } finally {
        bossGroup.shutdownGracefully();
        workerGroup.shutdownGracefully();
    }
}

// ==================================================

// 将拦截器 加入 plpeline 中
public class MyServerChannelInitializer extends ChannelInitializer<SocketChannel> {
    @Override
    protected void initChannel(SocketChannel ch)  {
        ch.pipeline() .addLast(new HttpRequestDecoder()) //http请求的解码器 
        ch.pipeline().addLast(new HttpObjectAggregator(1024 * 128)) 
        ch.pipeline().addLast(new HttpResponseEncoder()) //http响应的编码器 
        ch.pipeline().addLast(new ChunkedWriteHandler()) //支持异步的大文件上传 
        ch.pipeline().addLast(new ServerHandler());  //传输，防止内存溢出 
    }
}

// ==================================================
public class ServerHandler extends SimpleChannelInboundHandler<FullHttpRequest> {
    @Override
    public void channelRead0(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {
        //解析FullHttpRequest，得到请求参数
        Map<String, String> paramMap = new RequestParser(request).parse();
        String name = paramMap.get("name");
        //构造响应对象
        FullHttpResponse httpResponse = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK);
        httpResponse.headers().set(HttpHeaderNames.CONTENT_TYPE, "text/html;charset=utf-8");
        StringBuilder sb = new StringBuilder();
        sb.append("<h1>");
        sb.append("你好，" + name);
        sb.append("</h1>");
        httpResponse.content().writeBytes(Unpooled.copiedBuffer(sb, CharsetUtil.UTF_8));
        ctx.writeAndFlush(httpResponse).addListener(ChannelFutureListener.CLOSE); //操作完成后，将channel 关闭
    }
}

// ==================================================

// HTTP请求参数解析器, 支持GET, POST 
public class RequestParser {
    private FullHttpRequest fullReq;

    // 构造一个解析器 * @param req 
    public RequestParser(FullHttpRequest req) {
        this.fullReq = req;
    }
    
    /*** 
     * 解析请求参数 * @return 包含所有请求参数的键值对, 如果没有参数,
     */
    public Map<String, String> parse() throws Exception {
        HttpMethod method = fullReq.method();
        Map<String, String> parmMap = new HashMap<>();
        if (HttpMethod.GET == method) {
            // 是GET请求
            QueryStringDecoder decoder = new QueryStringDecoder(fullReq.uri());
            decoder.parameters().entrySet().forEach(entry -> {
                // entry.getValue()是一个List, 只取第一个元素
                parmMap.put(entry.getKey(), entry.getValue().get(0));
            });
        } else if (HttpMethod.POST == method) { // 是POST请求
            HttpPostRequestDecoder decoder = new HttpPostRequestDecoder(fullReq);
            decoder.offer(fullReq);
            List<InterfaceHttpData> parmList = decoder.getBodyHttpDatas();
            for (InterfaceHttpData parm : parmList) {
                Attribute data = (Attribute) parm;
                parmMap.put(data.getName(), data.getValue());
            }
        } else { // 不支持其它方法
            throw new RuntimeException("不支持其它方法"); // 这是个自定义的异常, 可删 掉这一行
        }
        return parmMap;
    }
}