【Netty】实战：基于Http的Web服务器

一、实现ChannelHandler

二、实现ChannelInitializer

三、实现服务器启动程序

四、测试

本文来实现一个简单的Web服务器，当用户在浏览器访问Web服务器时，可以返回响应的内容给用户。很简单，就三步。

一、实现ChannelHandler

package cn.md.netty.httpserver;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.*;
import io.netty.util.CharsetUtil;/*** * @Author: Martin* * @Date    2024/9/1 17:47* * @Description**/
public class HttpServerHandler extends SimpleChannelInboundHandler<FullHttpRequest> {/*** Is called for each message of type {@link I}.** @param ctx the {@link ChannelHandlerContext} which this {@link SimpleChannelInboundHandler}*            belongs to* @param msg the message to handle* @throws Exception is thrown if an error occurred*/@Overrideprotected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest msg) throws Exception {// 打印Http请求printHttpRequest(msg);String uri = msg.uri();String resp;switch (uri) {case "/":resp = "hello world";break;case "/test":resp = "test";break;case "/hi":resp = "hello";break;default:resp = "404";}// 返回http格式响应returnHttpResp(ctx, resp);}private void returnHttpResp(ChannelHandlerContext ctx, String msg) {FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK,Unpooled.copiedBuffer(msg, CharsetUtil.UTF_8));response.headers().set(HttpHeaderNames.CONTENT_LENGTH,msg.length());ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE_ON_FAILURE);}private void printHttpRequest(FullHttpRequest msg) {String uri = msg.uri();HttpMethod method = msg.method();HttpVersion httpVersion = msg.protocolVersion();// 打印请求行System.out.println("uri:" + uri + " method:" + method + " httpVersion:" + httpVersion);HttpHeaders headers = msg.headers();for (String name : headers.names()) {System.out.println(name + ":" + headers.get(name));}System.out.println("");System.out.println(msg.content().toString(CharsetUtil.UTF_8));}
}

二、实现ChannelInitializer

package cn.md.netty.httpserver;import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpServerCodec;/*** * @Author: Martin* * @Date    2024/9/1 17:55* * @Description**/
public class HttpServerChannelInitializer extends ChannelInitializer<SocketChannel> {/*** This method will be called once the {@link Channel} was registered. After the method returns this instance* will be removed from the {@link ChannelPipeline} of the {@link Channel}.** @param ch the {@link Channel} which was registered.* @throws Exception is thrown if an error occurs. In that case it will be handled by*                   {@link #exceptionCaught(ChannelHandlerContext, Throwable)} which will by default close*                   the {@link Channel}.*/@Overrideprotected void initChannel(SocketChannel ch) throws Exception {// 添加自定义的handlerch.pipeline().addLast("codec",new HttpServerCodec()) // 添加编解码器// 添加聚合器，聚合为一个完整的 FullHttpMessage.addLast("aggregator",new HttpObjectAggregator(1024*1024*10)).addLast("handler",new HttpServerHandler());}
}

三、实现服务器启动程序

package cn.md.netty.httpserver;import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelOption;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;/*** * @Author: Martin* * @Date    2024/9/1 18:01* * @Description**/
public class HttpServer {public static void main(String[] args) {NioEventLoopGroup bossGroup = new NioEventLoopGroup(1);NioEventLoopGroup workerGroup = new NioEventLoopGroup();ServerBootstrap serverBootstrap = new ServerBootstrap();try {ChannelFuture channelFuture = serverBootstrap.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class).childHandler(new HttpServerChannelInitializer())//服务器在处理客户端连接请求时的等待队列长度。//当服务器接收到客户端的连接请求时，如果服务器正在处理其他连接或者处于忙碌状态，新的连接请求将被放入等待队列中。.option(ChannelOption.SO_BACKLOG, 128)//底层套接字级别设置的选项，由操作系统的 TCP/IP 协议栈实现保活机制。//当开启后，在一定时间没有数据传输时，操作系统自动发送保活探测报文来检测连接是否仍然有效。.option(ChannelOption.SO_KEEPALIVE, true).bind(8888).sync();channelFuture.channel().closeFuture().sync();} catch (InterruptedException e) {throw new RuntimeException(e);} finally {workerGroup.shutdownGracefully();bossGroup.shutdownGracefully();}}}