一、Netty异步和事件驱动
1.Java网络编程回顾
socket.accept 阻塞
socket.setsockopt /非阻塞
2.NIO异步非阻塞
a).nio 非阻塞的关键时使用选择器(java.nio.channels.Selector)来实现；可以监控多个socket读写的完成状态来协调其他socket的读写，以提高资源使用率；
b).异步事件驱动，socket请求发起，立即响应，后端执行处理请求，处理完毕通知客户端；
c).Channel 链接实体的连接，请求和响应的载体；Netty通过回调来处理事件，时间触发->ChannelHandler->channelActive()来处理事件；
d).ChannelFuture通过ChannelFutureListener来监听事件提供通知处理完成的结果；Future是需要手动去获取结果；每个I/O操作都会立即返回一个ChannelFuture，不会阻塞，后台处理I/O,至于何时处理完成，异步时间驱动通知；
3.Nttey的异步变成模型建立在Future和回调的基础之上，再将时间派发到ChannelHandler之上进行处理；
二、Netty Demo
1.EchoServerHandler
package chap01;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.util.CharsetUtil;
@ChannelHandler.Sharable
public class EchoServerHandler extends ChannelInboundHandlerAdapter {
@Override
public void channelRead(ChannelHandlerContext ctx,Object msg){
ByteBuf in = (ByteBuf) msg;
System.out.println("Server received: "+ in.toString(CharsetUtil.UTF_8));
ctx.write(in);
}
@Override
public void channelReadComplete(ChannelHandlerContext ctx){
ctx.writeAndFlush(Unpooled.EMPTY_BUFFER).addListener(ChannelFutureListener.CLOSE);
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx,Throwable cause){
cause.printStackTrace();
ctx.close();
}
}
2.EchoServer
package chap01;
import io.netty.bootstrap.ServerBootstrap;
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.NioServerSocketChannel;
import java.net.InetSocketAddress;
public class EchoServer {
private final int port;
public EchoServer(int port){
this.port = port;
}
public static void main(String[] args) throws Exception{
// if (args.length !=-1){
// System.err.println("Usage: " + EchoServer.class.getSimpleName()+"<port>");
// }
// int port = Integer.parseInt(args[0]);
// new EchoServer(port).start();
new EchoServer(9001).start();
}
public void start() throws Exception{
final EchoServerHandler serverHandler = new EchoServerHandler();
EventLoopGroup group = new NioEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.group(group).channel(NioServerSocketChannel.class).localAddress(new InetSocketAddress(port)).childHandler(new ChannelInitializer<SocketChannel>(){
@Override
public void initChannel(SocketChannel ch) throws Exception{
ch.pipeline().addLast(serverHandler);
}
});
ChannelFuture f = b.bind().sync();
f.channel().closeFuture().sync();
}finally {
group.shutdownGracefully().sync();
}
}
}
3.EchoClientHandler
package chap01;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.util.CharsetUtil;
public class EchoClientHandler extends SimpleChannelInboundHandler<ByteBuf> {
@Override
public void channelActive(ChannelHandlerContext ctx){
ctx.writeAndFlush(Unpooled.copiedBuffer("Netty rocks!", CharsetUtil.UTF_8));
}
@Override
public void channelRead0(ChannelHandlerContext ctx,ByteBuf in){
System.out.println("Client received: "+in.toString(CharsetUtil.UTF_8));
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx,Throwable cause){
cause.printStackTrace();
ctx.close();
}
}
4.EchoClient
package chap01;
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;
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 group = new NioEventLoopGroup();
try {
Bootstrap b = new Bootstrap();
b.group(group).channel(NioSocketChannel.class).remoteAddress(new InetSocketAddress(host,port)).handler(new ChannelInitializer<SocketChannel>(){
@Override
public void initChannel(SocketChannel ch) throws Exception{
ch.pipeline().addLast(new EchoClientHandler());
}
});
ChannelFuture f = b.connect().sync();
}finally {
group.shutdownGracefully().sync();
}
}
public static void main(String[] args) throws Exception{
// if (args.length!=2){
// System.err.println("Usage: "+EchoClient.class.getSimpleName() + "<host><port>");
// return;
// }
// String host = args[0];
// int port = Integer.parseInt(args[1]);
// new EchoClient(host,port).start();
new EchoClient("127.0.0.1",9001).start();
}
}
原文：https://www.cnblogs.com/therunningfish/p/10959225.html