什么是Netty?

Netty 是一个利用Java 的高级网络的能力，隐藏其背后的复杂性而提供一个易于使用的API 的客户端/服务器 框架。

Netty 与 Tomcat

Netty与tomcat 最大的区别在于通信协议。Tomcat 是基于Http 协议的，它的实质是一个基于Http协议的web 容器。

但是Netty 不一样，它能通过编程自定义各种协议，因为netty能够通过codec 自己来编码/解码 字节流。完成类似redis访问的功能。

这就是netty 和tomcat 最大的不同

Netty 实现接受http 请求及响应

NettyHttpServerHandler 实际处理的handler，可以处理get 和post 请求

package com.damai;
 
 
import com.alibaba.fastjson.JSONObject;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.DefaultFullHttpResponse;
import io.netty.handler.codec.http.FullHttpRequest;
import io.netty.handler.codec.http.FullHttpResponse;
import io.netty.handler.codec.http.HttpMethod;
import io.netty.handler.codec.http.HttpResponseStatus;
import io.netty.handler.codec.http.HttpVersion;
import io.netty.handler.codec.http.QueryStringDecoder;
import io.netty.handler.codec.http.multipart.DefaultHttpDataFactory;
import io.netty.handler.codec.http.multipart.HttpPostRequestDecoder;
import io.netty.handler.codec.http.multipart.InterfaceHttpData;
import io.netty.handler.codec.http.multipart.MemoryAttribute;
import io.netty.util.CharsetUtil;
import io.netty.util.internal.StringUtil;
 
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
 
/**
 * @ClassName NettyHttpServerHandler
 * @Description 自定义处理的Handler
 * @Author xl
 * @Date 2019/8/27 11:30
 * @Version 1.0
 */
public class NettyHttpServerHandler extends SimpleChannelInboundHandler<FullHttpRequest> {
    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, FullHttpRequest fullHttpRequest) throws Exception {
        System.out.println(fullHttpRequest);
        
        FullHttpResponse response = null;
        if(fullHttpRequest.method() == HttpMethod.GET){
            System.out.println(getGetParamsFromChannel(fullHttpRequest));
            String data = "GET method over";
            ByteBuf buf = copiedBuffer(data, CharsetUtil.UTF_8);
            response = responseOk(HttpResponseStatus.OK,buf);
        }else if(fullHttpRequest.method() == HttpMethod.POST){
            System.out.println(getPostParamsFromChannel(fullHttpRequest));
            String data = "POST method over";
            ByteBuf buf = copiedBuffer(data, CharsetUtil.UTF_8);
            response = responseOk(HttpResponseStatus.OK,buf);
        }else{
            response = responseOk(HttpResponseStatus.INTERNAL_SERVER_ERROR,null);
        }
        // 发送响应
        channelHandlerContext.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
    }
 
    private ByteBuf copiedBuffer(String data, Charset utf8) {
        return Unpooled.wrappedBuffer(data.getBytes());
    }
 
    private Map<String, Object> getPostParamsFromChannel(FullHttpRequest fullHttpRequest) {
        Map<String, Object> params = new HashMap<>();
        if(fullHttpRequest.method() == HttpMethod.POST){
            // 处理post 请求
            String strContentType = fullHttpRequest.headers().get("Content-Type").trim();
            if(StringUtil.isNullOrEmpty(strContentType)){
                return null;
            }
            if(strContentType.contains("x-www-form-urlencoded")){
                params = getFormParams(fullHttpRequest);
            }else if(strContentType.contains("application/json")){
                params = getJSONParams(fullHttpRequest);
            }else {
                return null;
            }
        }
        return params;
    }
 
    private Map<String, Object> getJSONParams(FullHttpRequest fullHttpRequest) {
        Map<String, Object> params = new HashMap<>();
 
        ByteBuf content = fullHttpRequest.content();
        byte[] reqContent = new byte[content.readableBytes()];
        content.readBytes(reqContent);
        String strContent = null;
        try {
            strContent = new String(reqContent, "UTF-8");
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
 
        JSONObject jsonParams = JSONObject.parseObject(strContent);
        for (Object key : jsonParams.keySet()) {
            params.put(key.toString(), jsonParams.get(key));
        }
 
        return params;
 
    }
 
    private Map<String, Object> getFormParams(FullHttpRequest fullHttpRequest) {
        Map<String, Object> params = new HashMap<>();
 
        HttpPostRequestDecoder decoder = new HttpPostRequestDecoder(new DefaultHttpDataFactory(false), fullHttpRequest);
        List<InterfaceHttpData> postData = decoder.getBodyHttpDatas();
 
        for (InterfaceHttpData data : postData) {
            if (data.getHttpDataType() == InterfaceHttpData.HttpDataType.Attribute) {
                MemoryAttribute attribute = (MemoryAttribute) data;
                params.put(attribute.getName(), attribute.getValue());
            }
        }
 
        return params;
    }
 
    private FullHttpResponse responseOk(HttpResponseStatus status, ByteBuf buf) {
        FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1,
                status,buf);
        if(buf != null){
            response.headers().set("Content-Type","text/plain;charset=UTF-8");
            response.headers().set("Content-Length",response.content().readableBytes());
        }
        return response;
    }
 
    private Map<String, Object> getGetParamsFromChannel(FullHttpRequest fullHttpRequest) {
        Map<String, Object> params = new HashMap<>();
        if(fullHttpRequest.method() == HttpMethod.GET){
            QueryStringDecoder decoder = new QueryStringDecoder(fullHttpRequest.uri());
            Map<String, List<String>> paramList = decoder.parameters();
 
            for(Map.Entry<String, List<String>> entry : paramList.entrySet()){
                params.put(entry.getKey(),entry.getValue().get(0));
            }
            return params;
        }
        return params;
    }
}

Server 端启动程序

package com.damai;
 
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpRequestDecoder;
import io.netty.handler.codec.http.HttpResponseEncoder;
import io.netty.handler.stream.ChunkedWriteHandler;
 
/**
 * @ClassName NettyHttpServer
 * @Description TODO
 * @Author xl
 * @Date 2019/8/27 12:09
 * @Version 1.0
 */
public class NettyHttpServer {
 
    private int inetPort;
 
    public NettyHttpServer(int inetPort) {
        this.inetPort = inetPort;
    }
 
    public int getInetPort() {
        return inetPort;
    }
 
    public void init() throws Exception {
 
        EventLoopGroup parentGroup = new NioEventLoopGroup();
        EventLoopGroup childGroup = new NioEventLoopGroup();
 
        try {
            ServerBootstrap server = new ServerBootstrap();
            // 1. 绑定两个线程组分别用来处理客户端通道的accept和读写时间
            server.group(parentGroup, childGroup)
                    // 2. 绑定服务端通道NioServerSocketChannel
                    .channel(NioServerSocketChannel.class)
                    // 3. 给读写事件的线程通道绑定handler去真正处理读写
                    // ChannelInitializer初始化通道SocketChannel
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
                            // 请求解码器
                            socketChannel.pipeline().addLast("http-decoder", new HttpRequestDecoder());
                            // 将HTTP消息的多个部分合成一条完整的HTTP消息
                            socketChannel.pipeline().addLast("http-aggregator", new HttpObjectAggregator(65535));
                            // 响应转码器
                            socketChannel.pipeline().addLast("http-encoder", new HttpResponseEncoder());
                            // 解决大码流的问题，ChunkedWriteHandler：向客户端发送HTML5文件
                            socketChannel.pipeline().addLast("http-chunked", new ChunkedWriteHandler());
                            // 自定义处理handler
                            socketChannel.pipeline().addLast("http-server", new NettyHttpServerHandler());
                        }
                    });
            // 4. 监听端口（服务器host和port端口），同步返回
            // ChannelFuture future = server.bind(inetHost, this.inetPort).sync();
            ChannelFuture future = server.bind(this.inetPort).sync();
            // 当通道关闭时继续向后执行，这是一个阻塞方法
            future.channel().closeFuture().sync();
        } finally {
            childGroup.shutdownGracefully();
            parentGroup.shutdownGracefully();
        }
    }
 
    public static void main(String[] args) {
        NettyHttpServer server = new NettyHttpServer(8080);
 
        try {
            server.init();
        } catch (Exception e) {
            e.printStackTrace();
            System.err.println("exception: " + e.getMessage());
        }
        System.out.println("server close!");
 
    }
 
}

服务端启动后，可以通过postman 进行请求模拟:

get请求：

HttpObjectAggregator$AggregatedFullHttpRequest(decodeResult: success, version: HTTP/1.1, content: CompositeByteBuf(ridx: 0, widx: 0, cap: 0, components=0))
GET /?abc=666 HTTP/1.1
cache-control: no-cache
Postman-Token: fc519c93-cb2b-4ef1-b002-9f5b02834bc2
User-Agent: PostmanRuntime/7.6.0
Accept: */*
Host: 127.0.0.1:8080
accept-encoding: gzip, deflate
Connection: keep-alive
content-length: 0
{abc=666}

post请求：

HttpObjectAggregator$AggregatedFullHttpRequest(decodeResult: success, version: HTTP/1.1, content: CompositeByteBuf(ridx: 0, widx: 17, cap: 17, components=1))
POST / HTTP/1.1
Content-Type: application/x-www-form-urlencoded
cache-control: no-cache
Postman-Token: de61613e-ef01-405f-9a24-3976449f3428
User-Agent: PostmanRuntime/7.6.0
Accept: */*
Host: 127.0.0.1:8080
accept-encoding: gzip, deflate
content-length: 17
Connection: keep-alive
{a=888, b=999, c=000}