传统Socket中，NIO和IO的比较（Nio知识回顾）
IO
阻塞点： server.accept(); 和
单线程情况下只能有一个客户端
用线程池可以有多个客户端连接，但是非常消耗性能
NIO
selector.select()会产生阻塞的效果，但是它其实是非阻塞的
为什么呢？
selector.select(1000); 1s检测一次
selector.wakeup(); 唤醒selector
可以任由我们控制休眠和唤醒操作，所以它其实是非阻塞型
要想更加了解NIO，请查看我的NIO专题
什么是netty
netty可以运用在那些领域？
1分布式进程通信
例如: hadoop、dubbo、akka等具有分布式功能的框架，底层RPC通信都是基于netty实现的，这些框架使用的版本通常都还在用netty3.x
2、游戏服务器开发
最新的游戏服务器有部分公司可能已经开始采用netty4.x 或 netty5.x
1、netty服务端hello world案例
1. 创建Server类
package com.netty;
import org.jboss.netty.bootstrap.ServerBootstrap;
import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.channel.Channels;
import org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory;
import org.jboss.netty.handler.codec.string.StringDecoder;
import java.net.InetSocketAddress;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/**
* Created by Fant.J.
* 2018/2/2 21:28
*/
public class Server {
public static void main(String[] args) {
//服务类
ServerBootstrap bootstrap = new ServerBootstrap();
//两个线程池
ExecutorService booss = Executors.newCachedThreadPool();
ExecutorService worker = Executors.newCachedThreadPool();
//设置niosocket工厂
bootstrap.setFactory(new NioServerSocketChannelFactory(booss,worker));
//设置管道工厂
bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
@Override
public ChannelPipeline getPipeline() throws Exception {
ChannelPipeline pipeline = Channels.pipeline();
//将网络传输中的字节码(ChannelBuffer) 转换成String 可看源码
pipeline.addLast("decoder",new StringDecoder());
//将管道交给HelloHandler处理
pipeline.addLast("helloHandler",new HelloHandler());
return pipeline;
}
});
bootstrap.bind(new InetSocketAddress(10101));
System.out.println("server start");
}
}
2. 创建HelloHandler类
需要继承SimpleChannelHandler类，然后重写几个基本方法
- messageReceived() 接受消息
- exceptionCaught() 捕获异常
- channelConnected() 建立连接
- channelDisconnected() 断开连接：必须是连接已经建立，关闭通道的时候才会触发。
- channelClosed() 关闭通道
package com.netty;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.*;
/**
* 接受消息
* Created by Fant.J.
* 2018/2/2 22:54
*/
public class HelloHandler extends SimpleChannelHandler{
/**
* Invoked when a message object (e.g: {@link ChannelBuffer}) was received
* from a remote peer.
* 接受消息
* @param ctx
* @param e
*/
@Override
public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
// int i = 1/0;
// System.out.println("messageReceived()");
// ChannelBuffer message = (ChannelBuffer) e.getMessage();
// String s = new String(message.array());
System.out.println(e.getMessage());
// System.out.println(s);
//回复数据
ChannelBuffer channelBuffer = ChannelBuffers.copiedBuffer("hi".getBytes());
ctx.getChannel().write(channelBuffer);
super.messageReceived(ctx, e);
}
/**
* Invoked when an exception was raised by an I/O thread or a
* {@link ChannelHandler}.
* 捕获异常
* @param ctx
* @param e
*/
@Override
public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) throws Exception {
System.out.println("exceptionCaught()");
super.exceptionCaught(ctx, e);
}
/**
* Invoked when a {@link Channel} is open, bound to a local address, and
* connected to a remote address.
* 建立连接
* @param ctx
* @param e
*/
@Override
public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
System.out.println("channelConnected() ");
super.channelConnected(ctx, e);
}
/**
* Invoked when a {@link Channel} was disconnected from its remote peer.
* 断开连接：必须是连接已经建立，关闭通道的时候才会触发。
* @param ctx
* @param e
*/
@Override
public void channelDisconnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
System.out.println("channelDisconnected()");
super.channelDisconnected(ctx, e);
}
/**
* Invoked when a {@link Channel} was closed and all its related resources
* were released.
* 关闭通道
* @param ctx
* @param e
*/
@Override
public void channelClosed(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
System.out.println("channelClosed()");
super.channelClosed(ctx, e);
}
}
因为网络之间传输是通过字节来传输，所以我们在messageReceived()方法里，获取到的message需要对其进行String转换。转换方法：
//先拿到message对应的channelbuffer对象
ChannelBuffer message = (ChannelBuffer) e.getMessage();
String s = new String(message.array());
同样，我们如果想要回复数据，也要将String转换成字节，这是实例中的一个例子：
//前面管道的实例化 这里省略，直接贴出给管道进行StringDecoder()处理代码
pipeline.addLast("decoder",new StringDecoder());
让我们来研究下原理，其实是这样转换的：
//创建一个ChannelBuffer对象，并赋值 字节
ChannelBuffer channelBuffer = ChannelBuffers.copiedBuffer("hi".getBytes());
//获取到Channel并执行write()方法
ctx.getChannel().write(channelBuffer);
github路径：https://github.com/jiaofanting/Java-nio-and-netty-spring-demo/tree/master/src/com/netty
2、netty客户端hello world案例
Client类
package com.netty.client;
import org.jboss.netty.bootstrap.ClientBootstrap;
import org.jboss.netty.channel.*;
import org.jboss.netty.channel.socket.nio.NioClientSocketChannelFactory;
import org.jboss.netty.handler.codec.string.StringDecoder;
import org.jboss.netty.handler.codec.string.StringEncoder;
import java.net.InetSocketAddress;
import java.util.Scanner;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/**
* Created by Fant.J.
* 2018/2/3 10:59
*/
public class Client {
public static void main(String []args){
//服务类
ClientBootstrap bootstrap = new ClientBootstrap();
//线程池
ExecutorService boss = Executors.newCachedThreadPool();
ExecutorService worker = Executors.newCachedThreadPool();
//socket工厂
bootstrap.setFactory(new NioClientSocketChannelFactory(boss,worker));
//管道工厂
bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
@Override
public ChannelPipeline getPipeline() throws Exception {
ChannelPipeline pipeline = Channels.pipeline();
pipeline.addLast("decoder",new StringDecoder());
pipeline.addLast("encoder",new StringEncoder());
pipeline.addLast("hiHandler",new HiHandler());
return pipeline;
}
});
//连接服务器
ChannelFuture connect = bootstrap.connect(new InetSocketAddress("127.0.0.1",10101));
Channel channel = connect.getChannel();
System.out.println("client start");
Scanner scanner = new Scanner(System.in);
while (true){
System.out.println("please input string");
channel.write(scanner.next());
}
}
}
HiHandler类
package com.netty.client;
import org.jboss.netty.channel.*;
/**
* 消息接受处理器
* Created by Fant.J.
* 2018/2/3 10:59
*/
public class HiHandler extends SimpleChannelHandler{
/**
* 接收消息
*/
@Override
public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
String s = (String) e.getMessage();
System.out.println(s);
super.messageReceived(ctx, e);
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) throws Exception {
System.out.println("exceptionCaught()");
super.exceptionCaught(ctx, e);
}
@Override
public void channelOpen(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
System.out.println("channelOpen()");
super.channelOpen(ctx, e);
}
@Override
public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
System.out.println("channelConnected()");
super.channelConnected(ctx, e);
}
@Override
public void channelDisconnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
System.out.println("channelDisconnected()");
super.channelDisconnected(ctx, e);
}
@Override
public void channelClosed(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
System.out.println("channelClosed()");
super.channelClosed(ctx, e);
}
}
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