Netty5入门教程
1、Netty是什么？
本质：JBoss做的一个Jar包
目的：快速开发高性能、高可靠性的网络服务器和客户端程序
优点：提供异步的、事件驱动的网络应用程序框架和工具
通俗的说：一个好使的处理Socket的东东
2、Netty的异步事件驱动模型主要涉及到下面几个核心的概念
Channel：表示一个与socket关联的通道
ChannelPipeline： 管道，一个Channel拥有一个ChannelPipeline，ChannelPipeline维护着一个处理链（严格的说是两 个：upstream、downstream），处理链是由很 多通道处理器ChannelHandler所构成，每个ChannelHandler处理完以 后会传递给链中的下一个通道处理器继续处理。
ChannelHandler：通道处理器，用户可以定义自己的处理句柄来处理每个请求，或发出请求前进行预处理，典型的有编码/解码器：decoder、encoder。
ChannelEvent：事件，是整个模型的处理对象，当产生或触发（fire）一个事件时，该事件会沿着ChannelPipeline处理链依次被处理。 ChannelFuture： 异步结果，这个是异步事件处理的关键，当一个事件被处理时，可以直接以ChannelFuture的形式直接返回，不用在当前操作中被阻塞。可以通过 ChannelFuture得到最终的执行结果，具体的做法是在ChannelFuture添加监听器listener，当操作最终被执行完 后，listener会被触发，我们可以在listener的回调函数中预定义我们的业务代码。
ChannelPipeline实际上维持了两个处理链：upstream、downstream。 Upstream一般处理来自Channel的读事件，而downstream一般处理向Channel的写事件。需要注意的是，这两个处理链是相互独立 的，在upstream链中传递到最后一个ChannelHandler处理后，不会再传递到downstream链中继续处理。
在downstream链的末端会有个ChannelSink处理，用户可以自定义这个ChannelSink的实现，系统也有个默认的实现，当downstream链中最后一个ChannelHandler处理完后会被传递给这个ChannelSink进行最后的处理。
3、Demo
3.1、NettyServer.java
package com.jacky.server;
import java.util.concurrent.TimeUnit;
import org.apache.log4j.Logger;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.ChannelPipeline;
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 io.netty.handler.codec.LengthFieldBasedFrameDecoder;
import io.netty.handler.timeout.IdleStateHandler;
public class NettyServer {
private static Logger logger = Logger.getLogger(NettyServer.class);
private int port;
public NettyServer(int port) {
this.port = port;
bind();
}
private void bind() {
EventLoopGroup boss = new NioEventLoopGroup();
EventLoopGroup worker = new NioEventLoopGroup();
try {
ServerBootstrap bootstrap = new ServerBootstrap();
bootstrap.group(boss, worker);
bootstrap.channel(NioServerSocketChannel.class);
bootstrap.option(ChannelOption.SO_BACKLOG, 1024); //连接数
bootstrap.option(ChannelOption.TCP_NODELAY, true); //不延迟，消息立即发送
bootstrap.childOption(ChannelOption.SO_KEEPALIVE, true); //长连接
bootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel socketChannel)
throws Exception {
ChannelPipeline p = socketChannel.pipeline();
p.addLast(new NettyServerHandler());
}
});
ChannelFuture f = bootstrap.bind(port).sync();
if (f.isSuccess()) {
logger.debug("启动Netty服务成功，端口号：" + this.port);
}
// 关闭连接
f.channel().closeFuture().sync();
} catch (Exception e) {
logger.error("启动Netty服务异常，异常信息：" + e.getMessage());
e.printStackTrace();
} finally {
boss.shutdownGracefully();
worker.shutdownGracefully();
}
}
public static void main(String[] args) throws InterruptedException {
NettyServer server= new NettyServer(9999);
}
}
3.2、NettyServerHandler.java
package com.jacky.server;
import java.io.UnsupportedEncodingException;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
public class NettyServerHandler extends ChannelHandlerAdapter {
@Override
public void channelRead(ChannelHandlerContext context, Object msg) {
ByteBuf buf = (ByteBuf) msg;
String recieved = getMessage(buf);
System.out.println("服务器接收到消息：" + recieved);
try {
context.writeAndFlush(getSendByteBuf("APPLE"));
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
/*
* 从ByteBuf中获取信息 使用UTF-8编码返回
*/
private String getMessage(ByteBuf buf) {
byte[] con = new byte[buf.readableBytes()];
buf.readBytes(con);
try {
return new String(con, "UTF-8");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
return null;
}
}
private ByteBuf getSendByteBuf(String message)
throws UnsupportedEncodingException {
byte[] req = message.getBytes("UTF-8");
ByteBuf pingMessage = Unpooled.buffer();
pingMessage.writeBytes(req);
return pingMessage;
}
}
3.3、NettyClient.java
package com.jacky.client;
import java.util.concurrent.TimeUnit;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
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 io.netty.handler.codec.LengthFieldBasedFrameDecoder;
import io.netty.handler.timeout.IdleStateHandler;
public class NettyClient {
/*
* 服务器端口号
*/
private int port;
/*
* 服务器IP
*/
private String host;
public NettyClient(int port, String host)
throws InterruptedException {
this.port = port;
this.host = host;
start();
}
private void start() throws InterruptedException {
EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
try {
Bootstrap bootstrap = new Bootstrap();
bootstrap.channel(NioSocketChannel.class);
bootstrap.option(ChannelOption.SO_KEEPALIVE, true);
bootstrap.group(eventLoopGroup);
bootstrap.remoteAddress(host, port);
bootstrap.handler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel socketChannel)
throws Exception {
socketChannel.pipeline().addLast(new NettyClientHandler());
}
});
ChannelFuture future = bootstrap.connect(host, port).sync();
if (future.isSuccess()) {
SocketChannel socketChannel = (SocketChannel) future.channel();
System.out.println("----------------connect server success----------------");
}
future.channel().closeFuture().sync();
} finally {
eventLoopGroup.shutdownGracefully();
}
}
public static void main(String[] args) throws InterruptedException {
NettyClient client = new NettyClient(9999, "localhost");
}
}
3.4、NettyClientHandler.java
package com.jacky.client;
import java.io.UnsupportedEncodingException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.TimeUnit;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
public class NettyClientHandler extends ChannelHandlerAdapter {
private ByteBuf firstMessage;
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
byte[] data = "服务器，给我一个APPLE".getBytes();
firstMessage=Unpooled.buffer();
firstMessage.writeBytes(data);
ctx.writeAndFlush(firstMessage);
}
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg)
throws Exception {
ByteBuf buf = (ByteBuf) msg;
String rev = getMessage(buf);
System.out.println("客户端收到服务器数据:" + rev);
}
private String getMessage(ByteBuf buf) {
byte[] con = new byte[buf.readableBytes()];
buf.readBytes(con);
try {
return new String(con, "UTF-8");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
return null;
}
}
}
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