Netty 3.x 简例

Netty是一个异步的、事件驱动的网络应用框架，可以用来快速开发高性的客户端、服务端程序。示例使用Netty 3.10.5


首先是Server部分的代码：

Server端主程序：

package com.sean.server;

import java.net.InetSocketAddress;
import java.util.concurrent.Executors;

import org.jboss.netty.bootstrap.ServerBootstrap;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelFactory;
import org.jboss.netty.channel.group.ChannelGroup;
import org.jboss.netty.channel.group.ChannelGroupFuture;
import org.jboss.netty.channel.group.DefaultChannelGroup;
import org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory;

public class Server {
private ChannelFactory factory;

public static ChannelGroup channelGroup = new DefaultChannelGroup();

public void start(){
// NioServerSocketChannelFactory用于创建基于NIO的服务端
// ServerSocketChannel。本身包含2种线程，boss线程和worker线程。
// 每个ServerSocketChannel会都会拥有自己的boss线程，
// 当一个连接被服务端接受（accepted），
// boss线程就会将接收到的Channel传递给一个worker线程处理，
// 而worker线程以非阻塞的方式为一个或多个Channel提供非阻塞的读写
factory = new NioServerSocketChannelFactory(
Executors.newCachedThreadPool(),	// boss线程池
Executors.newCachedThreadPool(),	// worker线程池
8);	// worker线程数

// ServerBootstrap用于帮助服务器启动
ServerBootstrap bootstrap = new ServerBootstrap(factory);

// 没有child.前缀，则该选项是为ServerSocketChannel设置
bootstrap.setOption("reuseAddress", true);
// 有child.前缀，则该选项是为Channel设置
//		bootstrap.setOption("child.tcpNoDelay", true);
//		bootstrap.setOption("child.keepAlive", true);

// 对每一个连接（channel），server都会调用
// ChannelPipelineFactory为该连接创建一个ChannelPipeline
ServerChannelPiplineFactory channelPiplineFactory =
new ServerChannelPiplineFactory();
bootstrap.setPipelineFactory(channelPiplineFactory);

// 这里绑定服务端监听的IP和端口
Channel channel = bootstrap.bind(new InetSocketAddress("127.0.0.1", 8000));
Server.channelGroup.add(channel);

System.out.println("Server is started...");
}

public void stop(){
// ChannelGroup为其管理的Channels提供一系列的批量操作
// 关闭的Channel会自动从ChannelGroup中移除
ChannelGroupFuture channelGroupFuture = Server.channelGroup.close();
channelGroupFuture.awaitUninterruptibly();
factory.releaseExternalResources();
System.out.println("Server is stopped.");
}

public static void main(String[] args) throws Exception {
Server server = new Server();
server.start();
Thread.sleep(30*1000);
server.stop();
}
}

PipelineFactory：

package com.sean.server;

import java.util.concurrent.Executor;

import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.channel.Channels;
import org.jboss.netty.handler.execution.OrderedMemoryAwareThreadPoolExecutor;

import com.sean.server.handler.ServerExecutionHandler;
import com.sean.server.handler.ServerLogicHandler;
import com.sean.server.handler.ServerReadDecoder;
import com.sean.server.handler.ServerWriteEncoder;

public class ServerChannelPiplineFactory implements ChannelPipelineFactory {

@Override
public ChannelPipeline getPipeline() throws Exception {
ServerReadDecoder serverReadDecoder = new ServerReadDecoder();
ServerWriteEncoder serverWriteEncoder = new ServerWriteEncoder();
Executor executor =
new OrderedMemoryAwareThreadPoolExecutor(4, 200, 200);
ServerExecutionHandler serverExecutionHandler =
new ServerExecutionHandler(executor);
ServerLogicHandler serverLogicHandler = new ServerLogicHandler();

// ChannelPipeline的源码中的javadoc介绍的非常详细，很有必要看一下
// ChannelPipeline是一个处理ChannelEvent的handler链
// 如果为读操作，ChannelEvent事件会从前到后依次被
// Upstream的handler处理
// serverReadDecoder -> serverLogicHandler
// 如果为写操作，ChannelEvent事件会从后至前依次被
// Downstream的handler处理
// serverLogicHandler -> serverWriteEncoder
ChannelPipeline channelPipeline = Channels.pipeline();
channelPipeline.addLast("1", serverReadDecoder);
channelPipeline.addLast("2", serverWriteEncoder);
channelPipeline.addLast("3", serverExecutionHandler);
channelPipeline.addLast("4", serverLogicHandler);

System.out.println(channelPipeline.hashCode());
return channelPipeline;
}

}

各个Handler：

package com.sean.server.handler;

import java.util.concurrent.Executor;

import org.jboss.netty.handler.execution.ExecutionHandler;

// 提供一个线程池
public class ServerExecutionHandler extends ExecutionHandler{

public ServerExecutionHandler(Executor executor) {
super(executor);
}
}

package com.sean.server.handler;

import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelFuture;
import org.jboss.netty.channel.ChannelFutureListener;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ChannelStateEvent;
import org.jboss.netty.channel.ExceptionEvent;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelHandler;

import com.sean.server.Server;

// SimpleChannelHandler提供了很多基本的handler方法用来重写
// 通常情况下足够使用了
public class ServerLogicHandler extends SimpleChannelHandler {
@Override
public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e)
throws Exception {
System.out.println("######channelConnected");
// channel group is thread safe
Server.channelGroup.add(e.getChannel());
System.out.println(e.getChannel().toString());
}

@Override
public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) {
System.out.println("######messageReceived");

// 经过了ServerReadDecoder的处理，这里可以直接得到String类型的message
String msg = (String)e.getMessage();
System.out.println("The message sent by client is : " + msg);

Channel ch = e.getChannel();
String str = "Hi, Client.";
// 由于IO操作是异步的，当方法返回时并不能保证IO操作一定完成了
// 因此返回一个ChannelFuture对象实例
// 该实例中保存了IO操作的状态信息
ChannelFuture cf = ch.write(str);
// 为ChannelFuture对象实例添加监听，如果数据发送完毕则关闭连接
cf.addListener(new ChannelFutureListener(){
@Override
public void operationComplete(ChannelFuture future)
throws Exception {
Channel ch = future.getChannel();
ch.close();
}
});

System.out.println("The message has sent to client.");
}

@Override
public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) {
e.getCause().printStackTrace();
Channel ch = e.getChannel();
ch.close();
}
}

package com.sean.server.handler;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.string.StringDecoder;
import org.jboss.netty.util.CharsetUtil;

// 解决接收流数据时，数据出现碎片化的问题
public class ServerReadDecoder extends StringDecoder{

@Override
protected Object decode(ChannelHandlerContext ctx, Channel channel,
Object msg) throws Exception {
System.out.println("######ServerReadDecoder");

// 从msg中取出的数据类型是ChannelBuffer的
byte[] buffer = ((ChannelBuffer)msg).array();
byte last = buffer[buffer.length - 1];
// 46 is '.'
if(last == 46)
// 并将ChannelBuffer转为String
return new String(buffer, CharsetUtil.UTF_8);
return null;
}
}

package com.sean.server.handler;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.string.StringEncoder;
import org.jboss.netty.util.CharsetUtil;

public class ServerWriteEncoder extends StringEncoder{

@Override
protected Object encode(ChannelHandlerContext ctx, Channel channel,
Object msg) throws Exception {
System.out.println("######ServerWriteEncoder");

String str = (String)msg;
// 通过ChannelBuffers工具，为指定编码的指定字符串分配缓存空间
// 并将String转为ChannelBuffer
ChannelBuffer channelBuffer =
ChannelBuffers.copiedBuffer(str, CharsetUtil.UTF_8);
return channelBuffer;
}
}

然后是Client部分的代码：

Client端主程序：

package com.sean.client;

import java.net.InetSocketAddress;
import java.util.concurrent.Executors;

import org.jboss.netty.bootstrap.ClientBootstrap;
import org.jboss.netty.channel.ChannelFactory;
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.NioClientSocketChannelFactory;

import com.sean.client.handler.ClientLogicHandler;
import com.sean.client.handler.ClientReadDecoder;
import com.sean.client.handler.ClientWriteEncoder;

public class Client {
public static void main(String[] args){
// 同服务端相同，只是这里使用的是NioClientSocketChannelFactory
final ChannelFactory factory = new NioClientSocketChannelFactory(
Executors.newCachedThreadPool(),
Executors.newCachedThreadPool(),
8);

// ClientBootstrap用于帮助客户端启动
ClientBootstrap bootstrap = new ClientBootstrap(factory);
// 由于客户端不包含ServerSocketChannel，所以参数名不能带有child.前缀
bootstrap.setOption("tcpNoDelay", true);
//		bootstrap.setOption("keepAlive", true);

bootstrap.setPipelineFactory(new ChannelPipelineFactory(){
@Override
public ChannelPipeline getPipeline() throws Exception {
ChannelPipeline channelPipeline =
Channels.pipeline(new ClientReadDecoder(),
new ClientWriteEncoder(), new ClientLogicHandler());

System.out.println(channelPipeline.hashCode());
return channelPipeline;
}
});

// 这里连接服务端绑定的IP和端口
bootstrap.connect(new InetSocketAddress("127.0.0.1", 8000));
System.out.println("Client is started...");
}
}

各个Handler：

package com.sean.client.handler;

import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelFuture;
import org.jboss.netty.channel.ChannelFutureListener;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ChannelStateEvent;
import org.jboss.netty.channel.ExceptionEvent;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelHandler;
import org.jboss.netty.channel.WriteCompletionEvent;

public class ClientLogicHandler extends SimpleChannelHandler {

@Override
public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e)
throws Exception {
System.out.println("######channelConnected");

Channel ch = e.getChannel();
String msg = "Hi, Server.";
ch.write(msg);
}

@Override
public void writeComplete(ChannelHandlerContext ctx, WriteCompletionEvent e)
throws Exception {
System.out.println("######writeComplete");
}

@Override
public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) {
System.out.println("######messageReceived");

String msg = (String)e.getMessage();
System.out.println("The message gotten from server is : " + msg);

ChannelFuture channelFuture = e.getChannel().close();
channelFuture.addListener(ChannelFutureListener.CLOSE);
}

@Override
public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) {
e.getCause().printStackTrace();
Channel ch = e.getChannel();
ch.close();
}
}

package com.sean.client.handler;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.string.StringDecoder;
import org.jboss.netty.util.CharsetUtil;

public class ClientReadDecoder extends StringDecoder{

@Override
protected Object decode(ChannelHandlerContext ctx, Channel channel,
Object msg) throws Exception {
System.out.println("######ClientReadDecoder");

byte[] buffer = ((ChannelBuffer)msg).array();
byte last = buffer[buffer.length - 1];
// 46 is '.'
if(last == 46)
return new String(buffer, CharsetUtil.UTF_8);
return null;
}
}

package com.sean.client.handler;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.string.StringEncoder;
import org.jboss.netty.util.CharsetUtil;

public class ClientWriteEncoder extends StringEncoder{

@Override
protected Object encode(ChannelHandlerContext ctx, Channel channel,
Object msg) throws Exception {
System.out.println("######ClientWriteEncoder");

String str = (String)msg;
ChannelBuffer channelBuffer =
ChannelBuffers.copiedBuffer(str, CharsetUtil.UTF_8);
return channelBuffer;
}
}

运行结果如下：

Server端后台日志：

Server is started...
1257526899
######channelConnected
[id: 0x88120865, /127.0.0.1:58887 => /127.0.0.1:8000]
######ServerReadDecoder
######messageReceived
The message sent by client is : Hi, Server.
######ServerWriteEncoder
The message has sent to client.
Server is stopped.

Client端后台日志：

1767582956
Client is started...
######channelConnected
######ClientWriteEncoder
######writeComplete
######ClientReadDecoder
######messageReceived
The message gotten from server is : Hi, Client.