Netty（2） - HelloWorld

Netty：作用场景。

1）Netty可以基于socket实现远程过程调用（RPC）。

2）Netty可以基于WebSocket实现长连接。

3）Netty可以实现Http的服务器，类似于Jetty，Tomcat等Servlet容器。

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Netty充当Http服务器，我们通过浏览器去访问服务器的资源，服务器端处理完之后给我们返回响应-----Helloworld。

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1）定义一个Server

 1 package com.foreign.netty.helloworld;
 2
 3 import io.netty.bootstrap.ServerBootstrap;
 4 import io.netty.channel.ChannelFuture;
 5 import io.netty.channel.EventLoopGroup;
 6 import io.netty.channel.nio.NioEventLoopGroup;
 7 import io.netty.channel.socket.nio.NioServerSocketChannel;
 8
 9 /**
10  * Created with IDEA
11  * author:foreign
12  * Date:2018/12/25
13  * Time:23:21
14  */
15 public class TestServer {
16     public static void main(String[] args) throws InterruptedException {
17         /**
18          * 两个事件循环组(死循环) boos接受连接并发送给worker
19          */
20         EventLoopGroup bossLooper = new NioEventLoopGroup();
21         EventLoopGroup workerLooper = new NioEventLoopGroup();
22
23         try {
24             /**
25              * ServerBootstrap 服务端启动
26              * NioServerSocketChannel 通道（反射）
27              */
28             ServerBootstrap serverBootstrap = new ServerBootstrap();
29             serverBootstrap.group(bossLooper, workerLooper).channel(NioServerSocketChannel.class).childHandler(new TestServerInitializer());
30
31             ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
32             channelFuture.channel().closeFuture().sync();
33         } finally {
34             bossLooper.shutdownGracefully();
35             workerLooper.shutdownGracefully();
36         }
37     }
38 }

2）定义一个Initializer

 1 package com.foreign.netty.helloworld;
 2
 3 import io.netty.channel.ChannelInitializer;
 4 import io.netty.channel.ChannelPipeline;
 5 import io.netty.channel.socket.SocketChannel;
 6 import io.netty.handler.codec.http.HttpServerCodec;
 7
 8 /**
 9  * Created with IDEA
10  * author:foreign
11  * Date:2018/12/25
12  * Time:23:32
13  */
14 public class TestServerInitializer extends ChannelInitializer<SocketChannel> {
15
16     /**
17      * 子处理器， channel被注册好，会被自动创建
18      * @param ch
19      * @throws Exception
20      */
21     @Override
22     protected void initChannel(SocketChannel ch) throws Exception {
23         ChannelPipeline pipeline = ch.pipeline();
24         //编解码
25         pipeline.addLast("httpServerCodec",new HttpServerCodec());
26         //自己定义的handler
27         pipeline.addLast("testHttpServerHandler",new TestHttpServerHandler());
28
29     }
30 }

3）定义一个Handler

1 package com.foreign.netty.helloworld;
 2
 3 import io.netty.buffer.ByteBuf;
 4 import io.netty.buffer.Unpooled;
 5 import io.netty.channel.ChannelHandlerContext;
 6 import io.netty.channel.SimpleChannelInboundHandler;
 7 import io.netty.handler.codec.http.*;
 8 import io.netty.util.CharsetUtil;
 9
10 import java.net.URI;
11
12 /**
13  * Created with IDEA
14  * author:foreign
15  * Date:2018/12/25
16  * Time:23:34
17  */
18 public class TestHttpServerHandler extends SimpleChannelInboundHandler<HttpObject> {
19     /**
20      * 把结果返回给客户端（回调）
21      */
22     @Override
23     protected void channelRead0(ChannelHandlerContext ctx, HttpObject msg) throws Exception {
24         if (msg instanceof HttpRequest) {
25
26             HttpRequest httpRequest = (HttpRequest) msg;
27
28             //获取请求的方法类型
29             System.out.println(httpRequest.method().name());
30
31             URI uri = new URI(httpRequest.uri());
32             if("/favicon.io".equals(uri)) {
33                 System.out.println("请求了favicon.io 图标");
34                 return;
35             }
36
37             ByteBuf content = Unpooled.copiedBuffer("Hello Netty", CharsetUtil.UTF_8);
38             FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, content);
39             response.headers().set(HttpHeaderNames.CONTENT_TYPE, "text/plain");
40             response.headers().set(HttpHeaderNames.CONTENT_LENGTH, content.readableBytes());
41
42             ctx.writeAndFlush(response);
43
44             ctx.channel().close();
45         }
46     }
47 }

4）gradle的配置

plugins {
    id 'java'
}

group 'com.foreign'
version '1.0-SNAPSHOT'

apply plugin: 'java'

sourceCompatibility = 1.8
targetCompatibility = 1.8

repositories {
    mavenCentral()
}

dependencies {
    implementation 'io.netty:netty-all:4.1.10.Final'
    testCompile (
            "junit:junit:4.11"
    )
}

5）运行结果：运行server，并访问该地址。

6）总结：

1）在TestServer类中，启动一个ServerBootStrap的服务器，里面有两个事件循环组，并且通childHandler关联处理器。

2）在TestServerInitializer中加载netty内置的handler和自己的handler。

3）在TestHttpServerHandler中返回数据到客户端。

7）项目代码：https://github.com/fk123456/Netty/