netty的第一个helloworld

一种比较流行的做法是服务端监听线程和IO线程分离,类似于Reactor的多线程模型,它的工作原理图如下:

另外一种描述:

bossGroup线程组实际就是Acceptor线程池,负责处理客户端的TCP连接请求,如果系统只有一个服务端端口需要监听,则建议bossGroup线程组线程数设置为1。

workerGroup是真正负责I/O读写操作的线程组,通过ServerBootstrap的group方法进行设置,用于后续的Channel绑定。

服务端启动类

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package cn.itcast_03_netty.sendstring.server;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import cn.itcast_03_netty.sendobject.coder.PersonDecoder;
/**
* • 配置服务器功能,如线程、端口 • 实现服务器处理程序,它包含业务逻辑,决定当有一个请求连接或接收数据时该做什么
*
* @author wilson
*
*/
public class EchoServer {
private final int port;
public EchoServer(int port) {
this.port = port;
}
public void start() throws Exception {
EventLoopGroup eventLoopGroup = null;
try {
//server端引导类
ServerBootstrap serverBootstrap = new ServerBootstrap();
//连接池处理数据
eventLoopGroup = new NioEventLoopGroup();
//装配bootstrap
serverBootstrap.group(eventLoopGroup)
.channel(NioServerSocketChannel.class)//指定通道类型为NioServerSocketChannel,一种异步模式,OIO阻塞模式为OioServerSocketChannel
.localAddress("localhost",port)//设置InetSocketAddress让服务器监听某个端口已等待客户端连接。
.childHandler(new ChannelInitializer<Channel>() {//设置childHandler执行所有的连接请求
@Override
protected void initChannel(Channel ch) throws Exception {
ch.pipeline().addLast(new EchoServerHandler());//注册handler
}
});
// 最后绑定服务器等待直到绑定完成,调用sync()方法会阻塞直到服务器完成绑定,然后服务器等待通道关闭,因为使用sync(),所以关闭操作也会被阻塞。
ChannelFuture channelFuture = serverBootstrap.bind().sync();
System.out.println("开始监听,端口为:" + channelFuture.channel().localAddress());
channelFuture.channel().closeFuture().sync();
} finally {
eventLoopGroup.shutdownGracefully().sync();
}
}
public static void main(String[] args) throws Exception {
new EchoServer(20000).start();
}
}

服务端回调方法(处理器)

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package cn.itcast_03_netty.sendstring.server;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import java.util.Date;
import cn.itcast_03_netty.sendobject.bean.Person;
//继承了ChannelInboundHandlerAdapter
public class EchoServerHandler extends ChannelInboundHandlerAdapter {
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
System.out.println("server 读取数据……");
//读取数据
ByteBuf buf = (ByteBuf) msg;
byte[] req = new byte[buf.readableBytes()];
buf.readBytes(req);
String body = new String(req, "UTF-8");
System.out.println("接收客户端数据:" + body);
//向客户端写数据
System.out.println("server向client发送数据");
String currentTime = new Date(System.currentTimeMillis()).toString();
ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes());
ctx.write(resp);
}
@Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
System.out.println("server 读取数据完毕..");
ctx.flush();//刷新后才将数据发出到SocketChannel
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
cause.printStackTrace();
ctx.close();
}
}

客户端现场模型

另外一种描述:

客户端启动类

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package cn.itcast_03_netty.sendstring.client;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import java.net.InetSocketAddress;
import cn.itcast_03_netty.sendobject.coder.PersonEncoder;
/**
* • 连接服务器 • 写数据到服务器 • 等待接受服务器返回相同的数据 • 关闭连接
*
* @author wilson
*
*/
public class EchoClient {
private final String host;
private final int port;
public EchoClient(String host, int port) {
this.host = host;
this.port = port;
}
public void start() throws Exception {
EventLoopGroup nioEventLoopGroup = null;
try {
// 客户端引导类
Bootstrap bootstrap = new Bootstrap();
// EventLoopGroup可以理解为是一个线程池,这个线程池用来处理连接、接受数据、发送数据
nioEventLoopGroup = new NioEventLoopGroup();
bootstrap.group(nioEventLoopGroup)//多线程处理
.channel(NioSocketChannel.class)//指定通道类型为NioServerSocketChannel,一种异步模式,OIO阻塞模式为OioServerSocketChannel
.remoteAddress(new InetSocketAddress(host, port))//地址
.handler(new ChannelInitializer<SocketChannel>() {//业务处理类
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ch.pipeline().addLast(new EchoClientHandler());//注册handler
}
});
// 链接服务器
ChannelFuture channelFuture = bootstrap.connect().sync();
channelFuture.channel().closeFuture().sync();
} finally {
nioEventLoopGroup.shutdownGracefully().sync();
}
}
public static void main(String[] args) throws Exception {
new EchoClient("localhost", 20000).start();
}
}

客户端回调方法(处理器)

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package cn.itcast_03_netty.sendstring.client;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import cn.itcast_03_netty.sendobject.bean.Person;
//继承了SimpleChannelInboundHandler
public class EchoClientHandler extends SimpleChannelInboundHandler<ByteBuf> {
// 客户端连接服务器后被调用
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
System.out.println("客户端连接服务器,开始发送数据……");
byte[] req = "QUERY TIME ORDER".getBytes();//消息
ByteBuf firstMessage = Unpooled.buffer(req.length);//发送类
firstMessage.writeBytes(req);//发送
ctx.writeAndFlush(firstMessage);//flush
}
// • 从服务器接收到数据后调用
@Override
protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {
System.out.println("client 读取server数据..");
// 服务端返回消息后
ByteBuf buf = (ByteBuf) msg;
byte[] req = new byte[buf.readableBytes()];
buf.readBytes(req);
String body = new String(req, "UTF-8");
System.out.println("服务端数据为 :" + body);
}
// • 发生异常时被调用
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
System.out.println("client exceptionCaught..");
// 释放资源
ctx.close();
}
}

参考:
Netty系列之Netty线程模型
Netty工作原理架构图