netty

Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients.

如何使用

关键在编写ServerInitializer和clientInitializer。

在其中会申明调用的handler以及调用的顺序。

在handler中我们会自定义自己的处理逻辑。分别继承SimpleChannelInboundHandler和ChannelOutboundHandlerAdapter 在读入和写出时分别调用不同子类的处理逻辑。每一个连接到来时都对应一个pipeline，互相不影响。

在netty中 ByteBuf 和nio 中ByteBuffer是不同的概念。

当需要写出时，推荐使用堆外内存

• pipeline

package demo1;
import io.netty.channel.Channel;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.http.HttpServerCodec;
import io.netty.handler.codec.http2.Http2ChannelDuplexHandler;
/**
 * @Author: small_double
 * @Date: 2019/10/2 上午11:01
 */
public class TestServerInitializer extends ChannelInitializer<SocketChannel> {

    @Override
    protected void initChannel(SocketChannel socketChannel) throws Exception {
        ChannelPipeline channelPipeline = socketChannel.pipeline();
        channelPipeline.addLast("httpServerCodec",new HttpServerCodec());
        channelPipeline.addLast("testServerHandler", new TestServerHandler());
    }
}

• Handler

  ```java

  package demo1;

import io.netty.buffer.ByteBuf; import io.netty.buffer.Unpooled; import io.netty.channel.ChannelHandlerContext; import io.netty.channel.SimpleChannelInboundHandler; import io.netty.handler.codec.http.DefaultFullHttpResponse; import io.netty.handler.codec.http.FullHttpMessage; import io.netty.handler.codec.http.FullHttpResponse; import io.netty.handler.codec.http.HttpHeaderNames; import io.netty.handler.codec.http.HttpObject; import io.netty.handler.codec.http.HttpRequest; import io.netty.handler.codec.http.HttpResponseStatus; import io.netty.handler.codec.http.HttpVersion; import io.netty.util.CharsetUtil;

import java.nio.ByteBuffer; import java.nio.charset.Charset;

/**

• @Author: small_double

• @Date: 2019/10/4 上午9:19 */ public class TestServerHandler extends SimpleChannelInboundHandler {

  @Override protected void channelRead0(ChannelHandlerContext channelHandlerContext, HttpObject httpObject) throws Exception { if (httpObject instanceof HttpRequest) { HttpRequest httpRequest = (HttpRequest) httpObject; String uri = httpRequest.uri(); System.out.println(uri); ByteBuf byteBuf = Unpooled.copiedBuffer("hello world", CharsetUtil.UTF_8); HttpVersion version; HttpResponseStatus status; FullHttpResponse fullHttpResponse = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK,byteBuf); fullHttpResponse.headers().set(HttpHeaderNames.CONTENT_TYPE,"text/plain"); fullHttpResponse.headers().set(HttpHeaderNames.CONTENT_LENGTH,byteBuf.readableBytes()); channelHandlerContext.writeAndFlush(fullHttpResponse); } } }

- TestServer 基本是固定写法

```java
package demo1;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.EventLoop;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;

/**
 * @Author: small_double
 * @Date: 2019/10/2 上午10:46
 */
public class TestServer {
    public static void main(String[] args) {
        EventLoopGroup bossGroup=new NioEventLoopGroup(1);  //接收客户端连接的线程组
                EventLoopGroup workGroup=new NioEventLoopGroup(); //真正处理读写事件的线程组   16
                try {
                    ServerBootstrap serverBootstrap=new ServerBootstrap();
                    serverBootstrap.group(bossGroup,workGroup)
                            .channel(NioServerSocketChannel.class)  //服务端用什么通道
                            .childHandler(new TestServerLnitializer()); //已经连接上来的客户端
                    ChannelFuture channelFuture = serverBootstrap.bind(8989).sync();
                    channelFuture.channel().closeFuture().sync();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } finally {
                    bossGroup.shutdownGracefully();
                    workGroup.shutdownGracefully();
                }

    }
}

原理极其源码笔记