Netty因其易编程;高可靠性;高性能的网络IO;在分布式开发中被广泛用于网络通信;比如RocketMQ;Dubbo底层都能看到Netty的身影;高性能的本质是其Reactor线程模型以及异步的编程处理。Reactor有三种模型;常用的有主从 Reactor多线程模式;具体表现如下;
在日常开发中;常见基于Netty实现TCP报文传输;本文则基于Netty实现一个HTTP服务器;了解Netty的另一种用法。跟nginx类似;Netty在HTTP协议栈上也有优越的性能表现;不需要依赖Web容器;所以相比的Tomcat、Jetty等Web容器会更轻量和轻巧。
新建一个Pom工程;引入Netty的相关依赖;
io.nettynetty-all4.1.42.Final
定义Netty服务端NettyHttpServer用作HTTP服务端。创建bossGroup线程组和workerGroup线程组;bossGroup线程组分配一个线程用于轮询注册的通道;监听网络的连接事件;workerGroup用于处理网络的读写IO事件;不指定线程数则默认是CPU核数*2;
EventLoopGroup bossGroup = new NioEventLoopGroup(1); EventLoopGroup workerGroup = new NioEventLoopGroup();
同时定义服务启动助手ServerBootstrap;用于管理bossGroup和workerGroup;设置服务端通道实现为NIO;全连接队列的大小为1024;同时增加心跳检测的配置;具体代码如下;
serverBootstrap.group(bossGroup, workerGroup) .channel(NioServerSocketChannel.class) .option(ChannelOption.SO_BACKLOG, 1024) .childOption(ChannelOption.SO_KEEPALIVE, Boolean.TRUE) .childHandler()
接着初始化通道同时向pipeline中添加自定义的处理的handler;针对HTTP请求;Netty给我们提供了核心的HTTP编解码器HttpServerCodec;所以在通道初始化的时候增加HTTP编解码器;同时还有我们自定义的业务处理handler;具体代码如下;
serverBootstrap.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.option(ChannelOption.SO_BACKLOG, 1024)
.childOption(ChannelOption.SO_KEEPALIVE, Boolean.TRUE)
.childHandler(new ChannelInitializer() {;Override
protected void initChannel(SocketChannel ch) throws Exception {ch.pipeline().addLast(new HttpServerCodec());
// 自定义的业务处理handler
ch.pipeline().addLast(new NettyHttpServerHandler());
}
});之后启动服务端并绑定端口;同时将异步改为同步;之后监听通道关闭的状态和关闭连接池;服务端完整代码如下;
public class NettyHttpServer {private int port;
public NettyHttpServer(int port) {this.port = port;
}
public void run() throws InterruptedException {EventLoopGroup bossGroup = null;
EventLoopGroup workerGroup = null;
try {bossGroup = new NioEventLoopGroup(1);
workerGroup = new NioEventLoopGroup();
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.option(ChannelOption.SO_BACKLOG, 1024)
.childOption(ChannelOption.SO_KEEPALIVE, Boolean.TRUE)
.childHandler(new ChannelInitializer() {;Override
protected void initChannel(SocketChannel ch) throws Exception {ch.pipeline().addLast(new HttpServerCodec());
ch.pipeline().addLast(new NettyHttpServerHandler());
}
});
// 将异步改为同步
ChannelFuture future = serverBootstrap.bind(port);
future.addListener(new ChannelFutureListener() {;Override
public void operationComplete(ChannelFuture future) throws Exception {if (future.isSuccess()) {System.out.println(;端口; ; port ; ;绑定成功!;);
}
}
});
future.channel().closeFuture().sync();
} finally {bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
public static void main(String[] args) throws Exception {new NettyHttpServer(8080).run();
}
}剩下就是定义业务处理handler;NettyHttpServerHandler继承抽象类SimpleChannelInboundHandler用于接收数据的传入;类型为HttpObject。当服务端接收到HTTP的请求后;回一个响应”Hello! 我是Netty服务器“;具体代码如下;
public class NettyHttpServerHandler extends SimpleChannelInboundHandler{;Override
protected void channelRead0(ChannelHandlerContext ctx, HttpObject msg) throws Exception {//1.判断请求是不是HTTP请求
if (msg instanceof HttpRequest) {DefaultHttpRequest request = (DefaultHttpRequest) msg;
if (;/favicon.ico;.equals(request.uri())) {return;
}
//2.给浏览器进行响应
ByteBuf byteBuf = Unpooled.copiedBuffer(;Hello! 我是Netty服务器 ;, CharsetUtil.UTF_8);
DefaultFullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, byteBuf);
//2.1 设置响应头
response.headers().set(HttpHeaderNames.CONTENT_TYPE, ;text/html;charset=utf-8;);
response.headers().set(HttpHeaderNames.CONTENT_LENGTH, byteBuf.readableBytes());
ctx.writeAndFlush(response);
}
}
}启动服务端;显示端口绑定成功则说明服务端正常
流量器请求指定端口;可以看到在浏览器页面显示服务端返回的数据。
到这里;就完成基于Netty实现一个HTTP服务端;主要还是依赖于HTTP的编解码器HttpServerCodec;用于处理浏览器的GET请求;如果要实现POST请求;则需要依赖HttpObjectAggregator编解码器。
