Netty学习笔记（一）

学习圣思园Netty笔记，个人理解

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2.netty宏观理解-本节内容：

1.阶段性事件驱动，一个请求分为若干阶段处理，每个阶段根据情况合理分配线程去处理，各阶段间通信采用异步事件驱动方式。

2.netty5废弃原因，ForkJoinPool使netty开发复杂且性能提升不高。

3.netty大纲深度解读--本节内容：

了解google protobuf:Protocol Buffers\thrift\http\websocket这些概念

书籍推荐netty in action

4.项目环境搭建秘Gradle配置--本节内容

学习方法：先对整体了解，再去研究局部

Gradle:简洁，强大，灵活 推荐使用

Gradle安装方法：

1.下载

2.设置环境变量

For running Gradle, firstly add the environment variable GRADLE_HOME. This should point to the unpacked files from the Gradle website. Next add GRADLE_HOME/bin to your PATH environment variable. Usually, this is sufficient to run Gradle.

5.Netty执行流程分析与重要组件介绍--本节内容

本节实现了一个hello world例子，例子开始之前，我先把原理说一下（个人理解）：

Netty服务器通过监听通道发来的请求，并处理返回；在启动之前 ，要创建好处理请求的Event,同时定义监听的端口及处理请求的handler,最后关闭。具体 看代码

build.gradle文件

plugins {
    id 'java'
}
group 'com.nettydemo'
version '1.0-SNAPSHOT'
sourceCompatibility = 1.8
targetCompatibility = 1.8

repositories {
    //mavenCentral()
    maven { url 'http://maven.aliyun.com/nexus/content/groups/public/' }
}

dependencies {
    compile(
            "io.netty:netty-all:4.1.0.Final"
    )
}

TestServer.java

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

public class TestServer {

    public static void main(String[] args) throws InterruptedException {
        //接收客户端的请求，分配给workGroup
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        //真正的对连接处理的是workGroup
        EventLoopGroup workGroup = new NioEventLoopGroup();

        try{
            //简化服务端启动
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(bossGroup,workGroup).channel(NioServerSocketChannel.class)
                    .childHandler(new TestServerInitializer());//自定义的handler
            ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
            channelFuture.channel().closeFuture().sync();
        }finally {
            bossGroup.shutdownGracefully();
            workGroup.shutdownGracefully();
        }
    }
}

TestServerInitializer.java

import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.http.HttpServerCodec;
public class TestServerInitializer extends ChannelInitializer<SocketChannel> {
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline = ch.pipeline();
        pipeline.addLast("httpServerCodec",new HttpServerCodec());//非单例
        pipeline.addLast("testHttpServerHandler",new TestHttpServerHandler());
    }
}

TestHttpServerHandler.java

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.*;
import io.netty.util.CharsetUtil;

public class TestHttpServerHandler extends SimpleChannelInboundHandler<HttpObject> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, HttpObject msg) throws Exception {
        //读取客户端发来的请求，并返回响应
        ByteBuf content = Unpooled.copiedBuffer("Hello World!", CharsetUtil.UTF_8);//向客户端返回的数据
        FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK,content);
        response.headers().set(HttpHeaderNames.CONTENT_TYPE,"text/plain");
        response.headers().set(HttpHeaderNames.CONTENT_LENGTH,content.readableBytes());
        ctx.writeAndFlush(response);
    }
}